9- fixed that parameters passed on as variadic arguments to SCIPsolveNLP() and SCIPsolveNlpi() were ignored when compiling with MS compilers without -Zc:preprocessor
10- make more CONOPT output available when verbosity level is set to 2
11- turn off detection of definitional constraints in CONOPT for now, to work around a related issue in CONOPT 4.39.0
12- fixed call of SCIPcreateConsBasicSOCNonlinear() with coefs being NULL, and fixed check for offsets being finite
13- avoid crash when initial IIS solve fails while reporting errors explicitly
14- fixed that variable removal in IIS cleanup tried to delete variables that were marked as not deletable
15- fixed that some IIS info messages were not using a user's message handler
16- fixed use of interactive option (-i) of AMPL interface
17- fixed failure in nl writing on big endian machines
18- correct memory reallocation in storeSubproblemMasterVar() of benders.c to avoid errors when freeing memory
19- also set real solution in SCIPsolSetValExact() to maintain approximation
20- handle exact solutions in SCIPsolCheckOrig(), SCIPcheckSolOrig(), and SCIPrecomputeSolObj() to correctly check exact initial solutions in SCIPtransformProb()
21- fixed calculation of Euclidean norm in calcEfficacyDenseStorage() for use in exact solving
22- removed unnecessary explicit linking of GMP library for exact solving mode unittests
23- fixed bug with changing the type of the slack variable in indicator constraints while copying
24- signal extreme estimations in timeSeriesEstimate() and skip pruning estimations in eventExecEstim() to avoid unstable restarting
25- fixed parallelism computation of dynamic cut selector to use Euclidean norm instead of unsupported argument
26- fixed that non-efficacious cuts were not filtered out before checking dynamic parallelism in dynamic cut selector
27- fixes in nauty.h for 32bit systems
28- fixed SCIPgetDualSolVal() for a linear constraint with a single variable
29- adjust conflictAnalyzeLP() to inability of row aggregation to handle a change in the number of variables
30- propagate child lower bounds back to focus node to ensure consistent lower bound tracking
31
32Miscellaneous
33-------------
34
35- updated ampl/mp to version 4.0.4
36- switch from GetTempPath2A to GetTempPathA in nl writer for Windows for broader compatibility
37
38@section RN1000 SCIP 10.0.0
39***************************
40
41Features and Performance Improvements
42-------------------------------------
43
44### Exact Solving
45- added numerically exact solving mode for mixed-integer linear programs to the core framework including certification of branch-and-bound phase
46- core extensions:
47 - new wrapper struct SCIP_RATIONAL for rational arithmetic currently based on Boost, GMP, and MPFR
48 - new data structure SCIP_LPEXACT for handling rational LP relaxation and computing safe dual bounds
49 - new interfaces to exact LP solvers SoPlex and QSopt_ex
50 - safe dualproof version of conflict analysis
51 - new data structure SCIP_CERTIFICATE for certificate printing/proof logging
52- new plugins:
53 - new constraint handler "exactlinear" for handling linear constraints with rational data
54 - new constraint handler "exactsol" to post-process and repair solutions from floating-point heuristics
55- plugins revised for numerically exact solving mode:
56 - adjusted readers for MPS, LP, CIP, OPB/WBO, and ZIMPL files
57 - extended presolver "milp" to perform rational presolving with PaPILO
59 - extended Gomory cut separator to separate and certify numerically safe MIR cuts
60 - adjusted all primal heuristics (except for five dedicated MINLP heuristics)
61- new interfaces to exact LP solvers SoPlex and QSopt_ex
62
63### Symmetry Handling
64- added more techniques to handle reflection symmetries, in particular, for orbitopes with column reflections and matrices whose rows and columns can be permuted by a symmetry
65- Dejavu can be used to compute symmetries; the source code is shipped with SCIP and incorporates sassy
66- implemented symmetry detection callbacks for disjunction and superindicator constraint handlers
67- detailed information about applied symmetry handling techniques can be printed to the terminal
68- improve memory usage by introducing different constraint handlers for full orbitopes and packing/partitioning orbitopes
69- symmetry detection no longer treats implicit integer variables separately, but computes symmetries based on the variable type inferred from variable bounds and implied integrality
70- extended the statistics to also include information about the number of variables (per type) affected by symmetry
71- implemented method to compute new permutations from a given list of symmetry group generators
72- cons_orbisack, cons_orbitope_full, cons_orbitope_pp, and cons_symresack now try to replace the stored aggregated variables by active ones at the end of presolving;
73 this should reduce the size of copies of the presolved problem
74- simplified symmetry detection graphs in case all edges have the same color
75
76### Presolve
77- distinguish implicit integrality of variables into strong and weak type, depending on whether integrality is implied for all feasible or only at least one optimal solution
78- added a new presolver "implint", which detects implied integral variables by detecting (transposed) network submatrices in the problem; for now, this plugin is disabled by default
79- added support for (transposed) network matrix detection
80- allow multi-aggregation of unbounded slack variables, which may enable more bound tightening due to a reduction in the number of unbounded variables
81- resolve all fixings in xor constraints also for an available integer variable
82
83### Conflict Analysis
84- added generalized resolution conflict analysis that operates directly on linear constraints instead of conflict graphs
85- disabled dualsol and dualray conflict upgrades to maintain conflict store
86- apply general conflict upgrades in conflict store
87
88### Cutting Planes
89- added a new separator "flower" to generate flower cuts from AND constraints and nonlinear product expressions
90- added functionality to deal with hypergraphs by means of efficient access to vertices, edges, and intersections edges
91
92### Primal Heuristics
93- added decomposition kernel search (DKS) heuristic (disabled by default), which implements a kernel search framework;
94 it can be used both as a construction heuristic as well as an improvement heuristic; existing decomposition information can be utilized
95- reduced maximal fraction of diving LP iterations relative to total node LP iterations
96
97### Branching
98- added a dynamic max-lookahead criterion for strong branching; a probability distribution is fitted to the observed candidate gains and
99 evaluating further candidates stops when the expected tree-size reduction no longer justifies the LP evaluation cost
100- added new fields in history to store ancestral pseudo cost updates, used in the pseudo costs branching rule to compute discounted pseudo costs
101
102### Nonlinearity
103- added an interface to the NLP solver CONOPT
104- implemented columnwise Jacobian sparsity computation in the NLP oracle
108- added the possibility to search for irreducible infeasible subsystems (IIS)
109- added new plugin type for finding irreducible infeasible subsystems (IIS)
110- new iisfinder plugin "greedy", which implements a greedy addition and deletion based algorithm with dynamic batch sizing
111
112### Benders' Decomposition
113- when solving a problem with additional decomposition information (for example, when reading a DEC file) and enabling decomposition/applybenders,
114 the problem is now solved in a Benders' decomposition relaxator; instead of decomposing the original SCIP instance, the relaxator builds the decomposed problem in
115 sub-SCIPs and solves it via default Benders' Decomposition; a solution to the original (undecomposed) problem is now made available by the relaxator;
116 the SCIP shell dialog "display statistics" now also prints the statistics from solving the Benders' decomposition in the relaxator
117- adds objective types for Benders' decomposition; the choices are to sum the subproblems objectives (classical approach) and to use the maximum of the subproblems objectives
118- the linking master variables for each Benders' decomposition subproblem are now stored; these can be accessed for the generation of cuts and setting up the subproblems
119
120### Reading and Writing
121- added a new data structure SCIP_DATATREE that holds serializable data and a function to export to a JSON file
122- added ability to collect statistics from tables in a SCIP_DATATREE and write out as JSON file;
123 dialog write statistics now writes a JSON file if name of file to write ends with .json
124- added writing support for AMPL NL writer: currently only general and specialized linear and nonlinear constraints can be written
125- added support for AND-constraints to GAMS writer
126- simplify expressions of nonlinear constraints in MPS and LP writing to increase chance that they are recognized as quadratic
127
128### Applications
129- New application "PBSolver" to solve pseudoboolean instances in OPB and WBO format while complying with PB competition rules
130- Coloring: new parameter branching/coloring/strategy to choose the least/most fractional variable for branching
131
132### Miscellaneous
133- do not allow non-root restarts when no global fixings were found
134- reimplemented SCIPvarGetActiveRepresentatives() by using dense arrays to avoid repeated resorting
135- avoid unnecessary calls of constraint handlers components, benders, benderslp, propagator genvbounds, and heuristics ofins, subnlp, nlpdiving, indicator
136- inlined SCIPgetStatus() to reduce computational overhead
137- variable data pointer are now copied if no copy routine was supplied
138- add check that parameter value pointers are unique, i.e., no two are the same
139
140Interface changes
141-----------------
142
143### Deprecations
144
145- The variable type \ref SCIP_VARTYPE_IMPLINT is deprecated in favor of a new enum \ref SCIP_IMPLINTTYPE that indicates if a
146 variable is implied integral, independent of the variable type.
147 The problem variable arrays is still sorted as:
151 where the implied integral subsection is now subdivided into 3 parts (left to right):
152 ```
153 | binary implied integral | integer implied integral | continuous implied integral |
154 ```
155 SCIP 10 still supports using `SCIP_VARTYPE_IMPLINT` for backward compatibility, see SCIPcreateVar() and SCIPchgVarType() for more details.
156 SCIP 11 will remove `SCIP_VARTYPE_IMPLINT`.
157- SCIPsubversion() is deprecated and will be removed
158
159### New and changed callbacks
160
161- added SCIP_DECL_IISFINDERCOPY(), SCIP_DECL_IISFINDERFREE(), and SCIP_DECL_IISFINDEREXEC() for iisfinder implementations
162- added a new callback SCIP_DECL_TABLECOLLECT() for the table plugin that collects the data for the specific statistics table in a SCIP_DATATREE object
163- for a table plugin, only one of the callbacks SCIP_DECL_TABLECOLLECT() or SCIP_DECL_TABLEOUTPUT() needs to be implemented, but implementing both is preferred;
164 if SCIP_DECL_TABLEOUTPUT() is omitted, then SCIP tries to print a table from the data given by SCIP_DECL_TABLECOLLECT()
165- the callback SCIP_DECL_EXPRINTEGRALITY(), which returns the integrality of an expression, had its fourth argument changed from `SCIP_Bool*` to `SCIP_IMPLINTTYPE*` to represent implied integrality in nonlinear expressions,
166 that is, an implied integral type of an auxiliary variable if the expression were assigned to it
167- added argument `filename` to the SCIP_DECL_READERWRITE() callback in the 4th position
168- the callback SCIP_DECL_READERWRITE() is equipped with `objoffset`, `objscale`, `objoffsetexact`, and `objscaleexact` as arguments 9 through 12 to write the exact objective offset and scale in exact mode
169
170### Deleted and changed API functions
171
172- SCIPgetProbvarLinearSum(): remove parameter `mergemultiples`, which is now automatically true with the new implementation of SCIPvarGetActiveRepresentatives()
173- `SCIPcreateRow*()`, SCIPaddVarToRow(), SCIPaddVarsToRow(), SCIPaddVarsToRowSameCoef() can now only be called in the solving stage, because otherwise the LP is not yet available and the row data is invalid
174- SCIPcreateConsPseudobooleanWithConss(), SCIPcreateConsPseudoboolean(), and SCIPcreateConsBasicPseudoboolean(): removed `intvar` from arguments because the non-linear objective reformulation with pseudoboolean constraints did not work
175- SCIPcleanupConssLinear() and SCIPcleanupConssKnapsack(): added argument `ndelconss` to directly delete empty redundant constraints before creating problem matrix
179- SCIPpermuteProb(): argument `permuteimplvars` has been replaced by new arguments `permutebinimplvars`, `permuteintimplvars`, and `permutecontimplvars`
180- SCIPgetLPBranchCands(): implied integral variables with integrality constraints are included in `nlpcands` count and stored at the end of `lpcands`
181- SCIPgetNLPBranchCands(): implied integral variables with integrality constraints are included
182- SCIPgetSolVarsData(): argument `nimplvars` has been replaced by new arguments `nbinimplvars`, `nintimplvars`, and `ncontimplvars`
184- SCIPcreateVar() (temporarily for SCIP 10 only): attempting to create a variable with type \ref SCIP_VARTYPE_IMPLINT creates a variable of type \ref SCIP_VARTYPE_CONTINUOUS and implied integral type \ref SCIP_IMPLINTTYPE_WEAK
185- SCIPchgVarType() (temporarily for SCIP 10 only): attempting to change a variable type to \ref SCIP_VARTYPE_IMPLINT leads to a call of SCIPchgVarImplType() with type \ref SCIP_IMPLINTTYPE_WEAK
186- `SCIPapplyBendersDecomposition()` has been removed; this was originally used to apply Benders' decomposition from a supplied decomposition structure; the application of Benders' decomposition now occurs in relax_benders
187- SCIPcalcMIR(), SCIPcutGenerationHeuristicCMIR(), SCIPcalcStrongCG(): replaced boolean argument `usevbds` by an integer argument `vartypeusevbds`, which indicates for which variables variable bound substitution should be performed
188- `SCIPchgAndConsCheckFlagWhenUpgr()`, `SCIPchgAndConsRemovableFlagWhenUpgr()`: removed to keep upgrade flags consistent; use SCIPconsAddUpgradeLocks() to control upgrades instead
189- SCIPaddConflict(): argument `cons` changed to type `SCIP_CONS**` to release the conflict constraint in a clean way
190- SCIPprintOrigProblem() and SCIPprintTransProblem(): moved declaration moved from scip_solvingstats.h to scip_prob.h
191- `SCIPnlpiOracleGetJacobianSparsity()`: renamed to SCIPnlpiOracleGetJacobianRowSparsity() and added arguments `colnlflags` and `nnlnz`
205 `SCIPbendersApplyDecomposition()`, `SCIPgetExprsdataBilinear()`, `SCIPgetVarCoefChg()`, `SCIPvarGetOrigIndex()`, `SCIPallocateSymgraphConsnodeperm()`, `SCIPwriteSto()`: removed the declaration because there was no implementation
206
207### New API functions
208
209Exact Solving:
210- SCIPenableExactSolving(): enable and disable exact solving mode; see below for a list of many new API functions added to support exact solving
211- `SCIPrational*()`: create and compute with rational numbers
212- SCIPintervalSetRational(): compute interval of rational number
213- SCIPstrToRationalValue(), SCIPrationalStrLen(), SCIPrationalToString(): handle string conversion of a rational number
214- SCIPrationalChgInfinity(), SCIPrationalGetInfinity(): handle infinity threshold of rational numbers
215- `SCIPrationalarray*()`: create and handle rational arrays
216- SCIPisExact(): query whether exact solving is enabled
217- SCIPisCertified(): query whether certification is enabled
218- `SCIPcertify*()`, `SCIP*Certificate()`: support proof logging/certificate generation
219- `SCIP*MarkExact()`: mark plugins as safe to use in exact solving mode
220- `SCIP*IsExact()` : query whether objects are ready for exact solving
221- SCIPincludeConshdlrExactLinear(): include the constraint handler for exact linear constraints
222- `SCIP*ExactLinear()`: create, query, and modify an exact linear constraint
223- SCIPconsGetLhsExact()`, SCIPconsGetRhsExact(), SCIPgetConsValsExact(): query exact sides and coefficients of a linear constraint
224- `SCIPmatrix*Exact()`: query matrix information in rational arithmetic
225- SCIPaddVarExactData(): add exact data to an existing variable
226- `SCIPvarGet*Exact()`: query variable information in rational arithmetic
229- SCIPlpExactDiving(): query whether exact LP is in diving mode
230- SCIPlpExactIsSolved(): query whether the exact LP is solved
231- SCIPwriteLPexact(): write the exact LP
232- `SCIPcolExact*()`, `SCIProwExact*()`: handle the exact LP columns and rows
233- `SCIPlpiExact*()`: handle the exact LP interface
234- SCIPgetNExactLPs(): query the number of exact LP solves
235- SCIPgetLPExactSolstat(), SCIPgetLPExactObjval(): query solution status and objective value of the exact LP
236- SCIPaddOrigObjoffsetExact(), SCIPgetOrigObjoffsetExact(): add and query exact objective offset of the original problem
237- `SCIP*Sol*Exact()`: create and handle exact solutions
238- SCIPsolOrigAddObjvalExact(): add to exact objective of original solution
239- SCIPincludeConshdlrExactSol(): include the exact post-processing for solutions
240- `SCIP*Row*Exact*()`: create and handle exact LP rows
241- `SCIPaggrRow*Safely()`: compute safe real row aggregation
242- SCIPallowNegSlack(): query whether negative slacks are allowed
243- SCIPbranchLPExact(): branch exactly on the LP solution
244- SCIPeventGetOldboundExact(): query exact old bound for a bound change event
245- SCIPcalcIntegralScalarExact(): compute a scalar so that all given values become exactly integral
246- SCIPnodeGetLowerboundExact(): query the exact lower bound of a node
247- SCIPgetCutoffboundExact(), SCIPgetLowerboundExact(), SCIPgetUpperboundExact(), SCIPgetDualboundExact(), SCIPgetPrimalboundExact(): query exact best bounds on optimal value
248- SCIPvalidateSolveExact(): validate the exact solve
249
250Implicit Integrality:
251- SCIPincludePresolImplint(): include the new implied integral presolver
252- SCIPcreateVarImpl(), SCIPcreateObjVarImpl(): behave identically to SCIPcreateVar() and SCIPcreateObjVar(), respectively, but have an additional argument for the new implied integral type flag (8th position)
253- SCIPchgVarImplType(), SCIPvarGetImplType(), SCIPvarIsImpliedIntegral(), SCIPcolIsImpliedIntegral(): control and query implied integrality
254- SCIPvarIsNonimpliedIntegral(): query whether a variable is integral but not implied integral
255- SCIPgetNOrigBinImplVars(), SCIPgetNOrigIntImplVars(), SCIPgetNOrigContImplVars(): query the number of implied integral variables of each type in original problem;
256 note that SCIPgetNOrigBinVars(), SCIPgetNOrigIntVars(), and SCIPgetNOrigContVars() no longer include the implied integral variables in their counts
257- SCIPgetNBinImplVars(), SCIPgetNIntImplVars(), SCIPgetNContImplVars(): query the number of implied integral variables of each type in current problem;
258 note that SCIPgetNBinVars(), SCIPgetNIntVars(), and SCIPgetNContVars() no longer include the implied integral variables in their counts
259- SCIProwGetNumImpliedIntCols(): query number of implied integer columns in a row
260- SCIPvarsCountTypes(): determine the variable type count distribution for an array of variables
261- SCIPeventGetOldImplType(), SCIPeventGetNewImplType(): query implication type change for the new event \ref SCIP_EVENTTYPE_IMPLTYPECHANGED
262- SCIPexprGetIntegrality(): provides information about the presence of weakly implied integral variables, in addition to the existing function SCIPexprIsIntegral()
266- SCIPdisplaySymmetryGenerators(), SCIPdialogExecDisplaySymmetry(): display generators of symmetry group
267- SCIPclearSymgraph(), SCIPcopySymgraphAsSubgraph(): clear and copy a symmetry detection graph, respectively
268
269Conflict Analysis:
270- SCIPgetNResConflictConssApplied(): return the number of generalized resolution conflict constraints added to the problem
271- SCIPaddConsUpgrade(): add constraint upgrades while informing the conflict store
272
273Branching:
274- SCIPhistoryUpdateAncPseudocost(), SCIPvarUpdateAncPseudocost(): update the ancestral pseudo cost fields in variable history
275- SCIPhistoryGetAncPseudocost(), SCIPhistoryGetAncPseudocostCount(), SCIPhistoryIsAncPseudocostEmpty(), SCIPgetVarAncPseudocostVal(), SCIPvarGetAncPseudocost(): retrieve values related to ancestral pseudo cost fields in variable history
277- SCIPboundchgGetLPSolVal(): access LP solution value in the branching data of a bound change
278
279Cutting Planes:
280- SCIPincludeSepaFlower(): include the new flower cut separator
281- SCIPconsCreateRow(): to create and return the row of a linearly representable constraint
282- SCIPcreateRowKnapsack(), SCIPcreateRowLinear(), SCIPcreateRowLogicor(), SCIPcreateRowSetppc(), SCIPcreateRowVarbound(): create and get the row of linearly representable constraints
283
284Benders' Decomposition:
285- SCIPincludeRelaxBenders(): include the Benders' decomposition relaxator
286- SCIPgetMasterProblemRelaxBenders(): retrieve master problem SCIP instance from the Benders' decomposition relaxator
287- SCIPbendersGetSubproblemMasterVars(), SCIPbendersGetNSubproblemMasterVars(), SCIPbendersGetSubproblemMasterVarsData(): get the linking master variables for each subproblem and details about the number of binary and integer variables
288- SCIPsetBendersObjectiveType(), SCIPbendersGetObjectiveType(): set and get the objective type for the aggregation of the Benders' decompostion subproblems
289- SCIPbenderGetMasterAuxiliaryVar(): get master auxiliary variable
290- SCIPfreeReaderdataCor(), SCIPfreeReaderdataTim(), SCIPfreeReaderdataSto(): free the data for the COR, TIM, and STO readers, respectively; these readers are all used when reading an SMPS instance
303 SCIPhypergraphOverlapsEdgesGetAtIndex(), SCIPhypergraphVertexOverlapsFirst(), SCIPhypergraphVertexOverlapsBeyond(), SCIPhypergraphVertexOverlapsGetAtIndex(): query information about vertices, edges, and overlaps as well as their incidences
304
305Network Matrix:
306- SCIPnetmatdecCreate(), SCIPnetmatdecFree(): create and delete a network matrix decomposition
307- SCIPnetmatdecTryAddCol(), SCIPnetmatdecTryAddRow(): add columns and rows to a matrix decomposition
308- SCIPnetmatdecContainsRow(), SCIPnetmatdecContainsColumn(): check if a matrix decomposition contains the given row or columns
309- SCIPnetmatdecRemoveComponent(): remove connected components from a matrix decomposition
310- SCIPnetmatdecCreateDiGraph(): expose underlying digraph of matrix decomposition
311- SCIPnetmatdecIsMinimal(), SCIPnetmatdecVerifyCycle(): check whether certain invariants of a matrix decomposition are satisfied and used in tests
312
313Solve Statistics:
314- functions to create, modify, and free SCIP_DATATREE objects and to print as JSON or table (see pub_datatree.h and scip_datatree.h)
315- `SCIPcollect*Statistics()`: for every `SCIPprint*Statistics()` in scip_solvingstats.h
316- SCIPprintStatisticsJson(): output a JSON string of the table statistics data
317
318Nonlinearity:
319- SCIPincludeNlpSolverConopt(), SCIPsetLicenseConopt(), SCIPgetSolverNameConopt(), SCIPgetSolverDescConopt(), SCIPisConoptAvailableConopt(): interact with the new CONOPT interface
320- SCIPnlpiOracleGetConstraintLinearCoef(): get a linear coefficient of a variable in a given constraint in the NLP oracle
321- SCIPnlpiOracleGetJacobianColSparsity(): get the column-wise sparsity pattern of the Jacobian from the NLP oracle
322- SCIPnlpiOracleGetObjGradientNnz(): get indices of nonzeroes in the objective gradient
323- `src/objscip/objexprhdlr.h`: C++ interface for expression handlers
324
325Miscellaneous:
326- SCIPsortRealPtrPtr(), ..., SCIPsortDownIntIntIntReal(): new sorting functions
327- `SCIPdebugClearSol()`: clear the debug solution
328- SCIPdialogIsHidden(), SCIPdialogSetHidden(): determine whether a dialog should be hidden in help list
329- SCIPstatusName() to get a string representation of SCIP_STATUS
330- SCIPconshdlrSetNeedsCons(): set whether constraint handler callbacks should also be called if there are no constraints
331- SCIPpropSetTimingmask(): set timing mask of a propagator
333- SCIPvarGetMinAggrCoef(), SCIPvarGetMaxAggrCoef(): get bounds on absolute aggregation coefficients for a loose variable
334- SCIPisVarAggrCoefAcceptable(): check whether bounds on aggregation coefficients would exceed thresholds when using a loose variable in another aggregation
335- SCIPgetNRootIntFixings(): retrieve the number of integer fixings at the root node
336- SCIPcollectMemoryGarbage(): explicitly trigger garbage collection on block memory; before SCIP 10, this was done in SCIPtransformProb()
337
338### Data Structures
339
340- added struct \ref SCIP_RATIONAL for rational number arithmetic
341- added struct \ref SCIP_LPEXACT and many further data structures to support exact solving mode
343- added struct \ref SCIP_DATATREE to model generic serializable data; new enum \ref SCIP_DATATREE_VALUETYPE
344
345### Changes in Preprocessor Macros
346
347- `SCIP_EVENTTYPE_TYPECHANGED`: no longer generated if a variable becomes implied integral
348- `SCIP_EVENTTYPE_IMPLTYPECHANGED`: new event that is generated if a variable is declared implied integral, this event is included in the set \ref SCIP_EVENTTYPE_VARCHANGED
349- `SCIP_EVENTTYPE_DUALBOUNDIMPROVED`: new event that is generated whenever the global dual bound is improved
350- `SCIP_EVENTTYPE_GAPUPDATED`: new event mask for catching updates in primal or dual bound
351- `SCIP_PROPTIMING_NONE`: new propagator timing for never calling a propagator
352- `SCIP_HEURTIMING_NONE`: new heuristic timing for never call a primal heuristic
353- `strcasecmp`, `strncasecmp` (Windows builds): removed `#define` from scip/def.h; use SCIPstrcasecmp() and SCIPstrncasecmp() instead
360- `help <command>` now allows to display information on specific command
361- allow to hide certain commands in the help list
362- added the (hidden) command "exit" to exit the shell
363- added command `iis` to create an infeasible subsystem
364- added `write/iis` dialog to write out the infeasible subsystem to file
365- added `display/iis` dialog to write out the infeasible subsystem to console
366
367### Changed parameters
368
369- `heuristics/scheduler/heurtimelimit` removed to avoid indeterministic behavior of scheduler heuristic, uses main time limit instead
370- removed parameters `constraints/orbitope/checkpporbitope`, `constraints/orbitope/sepafullorbitope`, `constraints/orbitope/forceconscopy`, which became superfluous
371- removed `reading/gmsreader/signpower`
372- removed `benders/default/numthreads`: multi-threading support for Benders' decomposition has been temporarily disabled
373- restricted range of parameter `propagating/symmetry/sstleadervartype` to [1,7]; its new default value is 6
374- `propagating/∗/timingmask` extended by setting 0 to disable propagators completely
375- changed defaults of `constraints/components/propfreq` and `constraints/components/maxdepth` to -1 and 2147483647, respectively, to avoid unnecessary calls of components propagator by default
376- changed frequencies for the following heuristics: shifting, gins, crossover, rins, randrounding
377- changed default `maxlpiterquot` to 0.05 for all LP diving heuristics and feaspump, whereas adaptivediving uses 0.15 and rootsoldiving remains at 0.01
378- changed default of `presolving/restartminred` to 0.05
379- changed default of `presolving/immrestartfac` to 0.05
381- updated description of parameter `misc/usesymmetry`
382
383### New parameters
384
385- `exact/enable`: enable exact solving mode
386- `exact/improvingsols`: whether only improving exact solutions should be considered
387- `exact/safedbmethod`: method of safe dual bounding
388- `exact/interleavedbstrat`: interleaving strategy between safe dual bounding and exact LP solving
389- `exact/psdualcolselection`: project-and-shift strategy of dual column selection
390- `exact/cutapproxmaxboundval`: maximal absolute bound for which coefficients in exact cuts should be approximated
391- `exact/cutmaxdenom`: maximal denominator of coefficients in approximating exact cuts
392- `exact/allownegslack`: whether negative slack variables in exact Gomory cuts should be used
393- `exact/lpinfo`: whether the exact LP solver should display status messages
394- `constraints/exact{linear,sol}/{sepafreq,propfreq,proptiming,eagerfreq,maxprerounds,delaysepa,delayprop,presoltiming}`: functionality of constraint handlers exactlinear and exactsol
395- `constraints/exactlinear/sortvars`: whether binary variable coefficients should be sorted with decreasing absolute value in exactlinear constraints
396- `constraints/exactlinear/{tightenboundsfreq,propcont,limitdenom,boundmaxdenom}`: propagation of exactlinear constraints
397- `constraints/exactlinear/{maxrounds,maxroundsroot,maxsepacuts,maxsepacutsroot}`: separation of exactlinear constraints
398- `constraints/exactsol/solbufsize`: size of solution buffer in exactsol handler
399- `constraints/exactsol/{minimprove,checkfpfeasibility,checkcontimplint,abortfrac,unfixfrac}`: solution processing in exactsol handler
400- `constraints/exactsol/maxstalls`: maximal number of consecutive unsuccessful reparations in exactsol handler
402- `branching/pscost/discountfactor`, `branching/relpscost/discountfactor`: discount factor for ancestral pseudo costs in pscost and relpscost branching rules
403- `branching/collectancpscost`: enable/disable recording of ancestral pseudo costs
405 configure the dynamic max-lookahead criterion for strong branching: enable flag, fraction threshold, distribution choice, and minimum sample size
406- `constraints/cumulative/maxtime`: limit the time horizon and avoid integer overflow for unbounded variables
407- `constraints/orbitope_full/forceconscopy`, `constraints/orbitope_pp/forceconscopy`: whether non-model constraints of type full orbitope and packing/partitioning orbitope are copied to sub-SCIPs, respectively
408- `propagating/symmetry/handlesignedorbitopes`: whether to apply special symmetry handling techniques for orbitopes whose columns can be (partially) reflected
409- `propagating/symmetry/usesimplesgncomp:` whether symmetry components all of whose variables are simultaneously reflected by a symmetry shall be handled by a special inequality
410- `propagating/symmetry/dispsyminfo`: whether to print information about applied symmetry handling methods
411- `propagating/symmetry/nautymaxlevel`: limit on depth level of Nauty's search tree
412- `presolving/implint/convertintegers`: whether implied integrality should also be detected for enforced integral variables
413- `presolving/implint/columnrowratio`: ratio of rows/columns where the row-wise network matrix detection algorithm is used instead of the column-wise network matrix detection algorithm
414- `presolving/implint/numericslimit`: limit for absolute integral coefficients beyond which the corresponding rows and variables are excluded from implied integrality detection
415- `write/implintlevel`: whether integrality constraints should be written for implied integral variables (regarded by cip, mps, lp, rlp, pip, fzn, and gms writers)
416- `iis/∗`
417- `presolving/milp/enablecliquemerging`: whether to enable clique merging in PaPILO
418- `presolving/milp/maxedgesparallel`: maximal number of edges in the parallel clique merging graph
419- `presolving/milp/maxedgessequential`: maximal number of edges in the sequential clique merging graph
420- `presolving/milp/maxcliquesize`: maximal size of cliques considered for clique merging
421- `presolving/milp/maxgreedycalls`: maximal number of greedy max clique calls in a single thread
423- `relaxing/benders/continueorig`: whether original problem should continue solving after the completion of the Benders' decomposition algorithm in the Benders' relaxator, if the problem is not solved to optimality
424- `relaxing/benders/nodelimit`: node limit for the Benders' decomposition master problem in the Benders' relaxator; by default the limits from the original SCIP instance are copied
426- `lp/minsolvedepth`: lower bound on the depth at which LPs are solved
427- `reading/opbreader/maxintsize`: maximal intsize above which an OPB instance is rejected
428- `reading/nlreader/binary`, `reading/nlreader/comments`: adjust writing of `nl` files
429- `nlpi/conopt/priority`: priority of the CONOPT NLP solver
430- `randomization/randomseedshiftmultiplier`: multiplier for the shift set by `randomization/randomseedshift`;
431 the shift is multiplied by (6*`randomseedshiftmultiplier`+1), with the default value for `randomseedshiftmultiplier` set to 10 now;
432 this default value is expected to change with every major release; setting the parameter to 0 restores SCIP 9 behavior
433
434### Other Changes
435
436- removed LP solver interface `lpi_spx1`, which used the old SoPlex interface; renamed `lpi_spx2` to `lpi_spx`
437- removed `cons_abspower.{h,c}`, `cons_quadratic.{h,c}`, and `cons_soc.{h,c}`
438
439Build system
440------------
441
442- new option `SYM=dejavu` to choose Dejavu for computing symmetries
443- changed the default for `TPI` to `tny`
444- added build flag `CHECKSTAGE=auto` to control stage checks in API function calls
445- removed `LPS` options `spx1` and `spx2`, only `LPS=spx` is available to select SoPlex now
446- removed previously deprecated `PARASCIP` option, use `THREADSAFE=false` instead to disable thread-safety
447
448### Makefile
449
450- added build flag `EXACTSOLVE=<true|false|auto>` to turn exact solving mode on, off, or turn it on if all necessary dependencies are available
451- added build flag `MPFR` (default: false) to link with the multiprecision floating-point library, needed when SoPlex is also built with `MPFR=true` for precision boosting in rational solving mode
452- added build flag `CONOPT` (default: false) to link to the CONOPT NLP solver
453- link-time-optimization can be enabled on Linux and macOS with gcc and clang by setting `LTO=true`, default is false
454- revised `SANITIZE` options: removed `SANITIZE=full`, added `SANITIZE=thread`, `SANITIZE=address`, and `SANITIZE=memory` to enable thread, address, and memory sanitizers, respectively, in addition to undefined behavior sanitizer;
455 changed default to `SANITIZE=false`
456- default settings for makefile variables in `make.project` are now only used if variable hasn't been set already
457- the symlink `$(LIBDIR)/include/papilo` should now point to the `src` subdirectory of a PaPILO repository or the headers directory of a PaPILO installation without TBB; pointing to the directory of a PaPILO repository still works, but is deprecated
458- removed option to link TBB library, as this is not used by default when PaPILO has not been built via cmake (use `USRCXXFLAGS=-DPAPILO_TBB USRLDFLAGS=-ltbb` to enable TBB for PaPILO)
459- `LPS=spx` is no longer mapped to `LPS=spx2`, which changes the name of the generated LPI libraries and binaries when using SoPlex
460- removed `OPENSOURCE` flag
461
462### Cmake
463
464- added build flag `EXACTSOLVE=<on|off|auto>` to turn exact solving mode on, off, or turn it on if all necessary dependencies are available
465- added build flag CONOPT (default: off) to link to the CONOPT NLP solver and variable `CONOPT_DIR` to specify the path to CONOPT
466- link-time-optimization can be enabled if supported by compiler by using `-DLTO=on`, default is `off`
467- replaced `SANITIZE_XYZ=(on|off)` options by `SANITIZE=(on|off|thread|address|memory)`;
468 undefined behavior sanitizer is always enabled if not `SANITIZE=off` (the default)
469- increased minimal required cmake version to 3.11
470- scip-config.cmake now defines a variable `SCIP_COMPILE_FLAGS`, which could be used to compile code that builds against SCIP via cmake;
471 currently, this only passes on the sanitizer flags that were used to build `libscip`
472- removed automatic download and build of Bliss during cmake configuration when `-DSYM=(s)bliss`;
473 a Bliss installation from https://github.com/scipopt/bliss can be specified with `-DBLISS_DIR`
474- removed option `LEGACY`
475
476Fixed bugs
477----------
478
479- fixed bug related to unreleased data for the Benders' decomposition framework; when reading an SMPS file and applying
480 Benders' decomposition, data is created that was not correctly released; also, data within the Benders' decomposition
481 framework was not appropriately reset; the data is now released/reset as expected
482- to fix a bug where duplicate cuts from different constraint handlers were not recognized, `SCIPrealHash()` was changed
483 to be stable around shortly representable numbers, and a numerical tolerance for comparing cutting plane efficacy for the aggregation
484 separator is introduced
485- accept fractional continuous implied integral variables in heuristic "completesol"
486- invalidate activity with contradicting infinity contributions
487- avoid integer overflow in cumulative constraints triggered by unbounded variables, see new parameter `constraints/cumulative/maxtime`
488- allow negative update in SCIPconsAddUpgradeLocks() to unlock constraint upgrade
489- fixed memory leaks when LP, MPS, and OPB/WBO readers abort unsuccessfully
490- removed erroneous catching of objective-changed events in intobj separator; instead, the separator no longer executes within probing with changed objective function
491- propagator dualfix no longer fixes variables to infinity to avoid issues when transferring the solution to the original problem
492- track and check bounds on the coefficients that is used for a variable in aggregations of other variables to improve numerical stability
493- corrected the upgrade of full orbitopes to packing/partitioning orbitopes in case the orbitopal symmetries form a proper subgroup of a component's symmetry group
494- aggregate integer variable to not in clique variable in cliquePresolve() of xor constraints to avoid infeasible solutions
495- fixed memory leak in dynamic partition search primal heuristic
496- fixed issue with file existence check in XML parser when SCIP was build with ZLIB support on Windows
497- fixed thread-safety issue when using CppAD and user-defined expression handler
498- fixed typo in `#pragma` directive of redistributed nauty.h
499
500Miscellaneous
501-------------
502
503- removed 4th number in SCIP version; the new format is major.minor.patch
504- changed sassy to the version included in Dejavu
505- updated ampl/mp to v4.0.3
506- the CIP reader now sets an objective offset instead of adding a variable fixed to the objective offset
507- the solchecker tool has been extended for rational values
508- SCIPclassifyConstraintTypesLinear() classify a varbound only when a binary variable is present
509- the internal limit `MAXGENNUMERATOR` has been increased to allow more generators of symmetry groups, especially for problems with many variables
510
511@page RN9 Release notes for SCIP 9
512
513@section RN924 SCIP 9.2.4
514*************************
515
516Fixed bugs
517----------
518
519- fixed bugs with counting changes in presolving of nonlinear and setppc constraints, which resulted in negative values
520- cut off dead end node to correctly track dual bound update during solving
521- no longer construct and flush the LP in SCIPwriteLP() and SCIPwriteMIP() to avoid unexpected side effects
522- apply multi-aggregations before detecting redundancy in propagation of varbound constraints to keep bound implications
523- skip bound changes when cutting off a branch-and-bound subtree
524- correct detection of doublelex matrices and their handling via orbitope constraints
525- skip attempting to free transformed problem if SCIPtransformProb() failed with an error in SCIPpresolve(), since freeing
526 the transformed problem is likely to fail as well
527- fixed memory leak in primal heuristic "scheduler" when there is a restart
528- fixed stopping when there is a candidate with a change in the LP bound for both children in strong branching of branch_fullstrong
529- fixed detection of sinks in varbound detection from cumulative constraints
530- fixed memory allocation when adding strong SBCs for enclosing orbit of symmetric subgroups (disabled by default)
531- free paths of branch-and-bound tree iteratively instead of recursively to avoid stack overflow
532- fixed rare invalid memory access when collecting symmetry information for indicator constraints
533- recompute activity bounds before checking infeasibility and redundancy in linear constraint presolving
534- skip integer variables with fractional value in reference solution when finding additional variable fixings in ALNS heuristic
535- fix call of SCIPaddExprsViolScoreNonlinear() with constant expressions (no variables)
536- fixed bug with concurrent solve w.r.t. variable indices that led to segmentation faults and fix termination test
537- adjust further bounds before checking feasibility in SCIPvarAddVlb() and SCIPvarAddVub() to detect integrality cutoff
538- fixed that the last fixed binary variable was not set after binary variables were created for linking constraints
539- fixed that when a linking constraint with only one binary variable was added during solving, it was not disabled
540- fixed set_search_limits call when using SYM=sbliss with an old patched Bliss version
541
542Build system
543------------
544
545### CMake
546
547- added workaround for recent ctest versions rejecting -R -default as arguments
548
549### Makefile
550
551- added experimental target to run cppcheck
552
553
554@section RN923 SCIP 9.2.3
555*************************
556
557Fixed bugs
558----------
559
560- avoid hashmap key error in removal of doubletons and singletons in dual presolve of setppc constraints by skipping tripleton locks
561- when upgrading to xor constraint require parity variable to be enforced integral
562- provide the depth of the applied effective root with SCIPtreeGetEffectiveRootDepth() to avert invalid globalization of constraint set changes
563- disable objective limit during lexicographic dual minimization to preserve feasibility status
564- declare infinite bound inference infeasible in SCIPinferVarLbCons() and SCIPinferVarUbCons() to maintain correct loose LP values
565- fixed update of consssorted flags in a variable expressions data when adding an additional constraint using this variable
566- corrected computation of number of variables affected by symmetry
567- fixed computation of symmetry group size
568- correct comparison conditions in checkRedundancySide() of cons_varbound.c to ensure pair redundancy
569- also for the initial LP solve force acceptance of Farkas row in SCIPlpGetDualfarkas() if all other means for obtaining a reliable Farkas proof have failed
570- avoid overwriting the cutoff flag in tightenCoefs(), preprocessConstraintPairs(), and applyFixings() of cons_varbound.c to reject infeasible solutions
571- fix memory leak in CppAD interface w.r.t. user expressions
572- adjust bound before checking feasibility in SCIPvarAddVlb() and SCIPvarAddVub() to detect integrality cutoff
573- choose incumbent solution as reference in varFixingsRins() and varFixingsDins() of ALNS heuristic to ensure integrality
574- consider variable type in selectInitialVariableRandomly() of GINS heuristic to count integral variables
575- correct fractionality sign when standardizing bounds in simplifyInequalities() of cons_linear.c
576
577Build system
578------------
579
580### CMake
581
582- disable setting the boolean variable MACOSX_RPATH to a string value to actually enable @rpath usage
583- define SOPLEX_NEEDED and ZIMPL_NEEDED to avoid syntax error in configuration file
584
585Miscellaneous
586-------------
587
588- when writing a problem with non-generic names, warnings are printed if variable or constraint names are not unique
589
590@section RN922 SCIP 9.2.2
591*************************
592
593Fixed bugs
594----------
595
596- fixed definition of slack variables of >= constraints and ranged rows in LP interface to Gurobi
597- free memory leaking singleton arrays for ignored variables in SCIPapplyHeurDualval()
598- use epsilon tolerance for bound implications of dual substitutions in dualPresolve() of cons_linear
599- fixed timeouts due to race conditions when using TPI=omp
600- fixed issues with indexing of concurrent solvers when a solver finishes (because SCIP is too fast) before others have been created when using TPI=tny
601- respect fixing if variable is declared binary in bounds section of mps file
602- fixed reading mps files with short row and column names and some fixed-form mps files with spaces in row names
603- force local bounds to adjusted value when fixing variable
604- adds missing NULL check for Benders' subproblems in feasalt cut
605- apply objective scale to pseudoboolean non-linear terms
606- impose pseudoboolean cost bound without intermediate casting
607- flatten aggregation graph before finishing presolve to accelerate evaluating an empty solution
608- respect fixed resultants in binvarGetActiveProbindex() of branch_relpscost
609- drop fixed resultants when copying pseudoboolean constraint
610- correct matrix entry when resolving aggregated variables in checkSystemGF2() of cons_xor
611- corrected symmetry detection graph of cons_and, cons_or, cons_xor, and cons_indicator
612- correct redundancy filter in consdataCreateRedundant() of cons_bounddisjunction
613- replaced unreliable comparison of node pointers by node numbers in prop_genvbounds
614- allocate memory for all integral variables in applyCliqueFixings() of heur_clique
615- fix conflict resolution for one particular case in cons_indicator
616- make interface to nauty thread safe
617- use relative epsilon tolerance to check Farkas row in SCIPlpGetDualfarkas() to avoid invalid cutoff
618- fixed bug with SOS2 constraints of size that avoided a correct enforcing
619
620Build system
621------------
622
623### Cmake
624
625- allow to set HIGHS_DIR via -D flag as well
626- reenable building and testing of SCFLP example
627- fixed that compiler flags for sanitizers were not used for compiling objects of SCIP library
628- prioritize local includes for unittests, examples, and applications to link the intended SCIP version
629- fix detection of Gurobi 11 and 12 libs on Linux
630
631### Makefile
632
633- fix use of SANITIZE=full for debug builds with GCC on Linux: removed -fsanitize=leak because it cannot be used together with -fsanitize=address
634- fix that make install SHARED=true missed to install libscipbase
635
636@section RN921 SCIP 9.2.1
637*************************
638
639Fixed bugs
640----------
641
642- apply same feasibility definition in PaPILO as in SCIP to avoid numerical inconsistencies
643- check variable cancellation in SCIPvarAddVlb() and SCIPvarAddVub() to avert wrong infeasibility
644- SCIPfreeReoptSolve() now also clears partial solutions
645- fixed bug in calculation of "fractionality score" for spatial branching candidates in cons_nonlinear
646- fixed bug with installing symmetry dialog in sub-SCIPs
647- added copy callbacks for presolvers dualagg and redvub, branching rules lookahead and cloud, primal heuristics dualval and repair, propagator nlobbt, and separators gauge and convexproj
648- respect maximal separation rounds setting by running remaining delayed separators in last round
649- replace terms consistently in applyFixings() of cons_linear to handle infinite aggregations
650
651Build system
652------------
653
654### Cmake
655
656- fix SCIP Optimization Suite build with -DSYM=(s)bliss and bliss being downloaded and built during configuration by cmake
657- fix use of a bliss cmake installation (from https://github.com/scipopt/bliss) specified via BLISS_DIR if -DSYM=(s)bliss
658
659### Makefile
660
661- the check/solchecker build can now use also GMP installations by Homebrew on macOS/arm64
662
663Miscellaneous
664-------------
665
666- the output precision for writing CIP/OPB files has been increased at several places for nonlinear constraints
667- the solchecker tool now also supports SCIP solutions without unknown or infinite values
668- generate an error if the same linear constraint is used by several indicator constraints
669
670@section RN920 SCIP 9.2.0
671*************************
672
673Features
674--------
675
676- added check for absolute and relative gap limits at end of synchronization in concurrent solving mode, in order to terminate earlier;
677 note that if the concurrent solve is stopped due to a gap limit, the "winner" solver will have an interrupted solution status and
678 its primal and dual bounds may not be the best possible ones (use SCIPgetConcurrentPrimalbound() and SCIPgetConcurrentDualbound() instead)
679- parse pseudoboolean constraint from CIP format (and add linear-"and"-reformulation)
680
681
682Performance improvements
683------------------------
684
685- reoptimization now also stores propagations from propagators if reoptimization/saveconsprop is enabled;
686 the parameter will be renamed to reoptimization/saveprop in a next major release
687- imposed stricter limits on the size of disconnected components which may be solved separately during presolve
688- use individual slack variables also for constraints indicated by a common binary variable to use tighter formulation by default
689- when computing symmetries using Nauty, iteration limits are now available to terminate Nauty early
690
691Fixed bugs
692----------
693
694- Benders' decomposition subproblems that are always infeasible are correctly handled and the complete problem is declared infeasible
695- skip linear constraint propagation if the residual activity bound cancels the side precision
696- correct bound tracking to make the evaluation of primal-dual-integrals work
697- skip aggregations on fixed variables in milp presolver to avoid errors for earlier versions of PaPILO
698- use indices of negation counterparts and accept fixings when ordering and-resultants of pseudoboolean constraints
699- update locks on model variables before removing pseudoboolean constraints in presolve
700- reformulate soft pseudoboolean constraints with linear constraints if the indicator decomposition is disabled
701- add workaround for recent HiGHS versions resetting the model status when changing the presolve option after a solve
702- avoid hashmap key error in removal of doubletons and singletons in dual presolve of setppc constraints by updating constraints and corresponding hashmaps after each multi-aggregation
703
704Interface changes
705-----------------
706
707### New API functions
708
709- added SCIPtpiIsAvailable() to check whether a working task processing interface is available (TPI != none)
710- added SCIPtpiGetLibraryName() and SCIPtpiGetLibraryDesc()
711- SCIPdelCons() can now also be called in SCIP_STAGE_TRANSFORMED
712- added SCIPstrcasecmp() and SCIPstrncasecmp() for case-insensitive string comparison
713- added SCIPbendersSubproblemsAreInfeasible() to return if at least one subproblem has been identified as being
714 infeasible prior to performing any variable fixing
715
716### New parameters
717
718- presolving/milp/abortfacexhaustive to control the abort threshold for exhaustive presolving in PAPILO
719- presolving/milp/abortfacmedium to control the abort threshold for medium presolving in PAPILO
720- presolving/milp/abortfacfast to control the abort threshold for fast presolving in PAPILO
721- constraints/components/maxcompweight to determine the maximum weight for a disconnected component that is solved during presolve
722- constraints/components/contfactor counts the contributing factor of a single continuous variables with respect to the weight limit specified by constraints/components/maxcompweight
723- constraints/indicator/usesameslackvar to decide whether the same slack variable should be used for indicators constraints with common binary variable
724- propagating/symmetry/nautymaxncells and propagating/symmetry/nautymaxnnodes to set iteration limits in Nauty (only available if build with SYM=nauty or SYM=snauty)
725
726### Changed parameters
727
728- presolving/milp/threads is now only available if PaPILO is built with TBB
729- changed default of numerics/recomputefac to 1e+6 to aim at relative epsilon precision
730
731Build system
732------------
733
734### Cmake
735
736- attempted to fix detection of CPLEX library on macOS and Windows systems
737
738Testing
739-------
740
741- added parameter FILTER for tests/Makefile to run only tests with a specific pattern (ctest with -R FILTER)
742
743Miscellaneous
744-------------
745
746- adjusted Gurobi interface for Gurobi 12
747- reordered events: BESTSOLFOUND/NODE_FEASIBLE are now processed before the nodes are cut off and before NODE_DELETE events are processed
748- removed `#define` of `getcwd` (in case of Windows builds) in scip/def.h
749- the `#define` of `strcasecmp` and `strncasecmp` (in case of Windows builds) in scip/def.h will be removed with SCIP 10;
750 use `SCIPstr(n)casecmp()` (scip/pub_misc.h) instead
751
752@section RN911 SCIP 9.1.1
753*************************
754
755Fixed bugs
756----------
757
758- fix bug in separator aggregation that caused incorrect terminations when for an integral objective the objective limit was set to a fractional value
759- fix bug in memory management of doublelex matrices where indices were set beyond array bounds
760- store relevance flags in consdataTightenCoefs() of cons_linear.c to avoid dropping variables unintentionally due to numerical changes
761- fix possible segmentation fault when resetting local and global bounds of original variables after abnormal termination
762- compare coefficient scales to detect parallelism to avoid integral relaxations in detectRedundantConstraints() of cons_linear.c
763- remove coefficient information from linear constraint hashes in order to compare keys with tolerances
764- fixed NULL pointer dereference in SCIPtpiGetNumThreads() of TinyCThread interface if called before SCIPtpiInit(); now returns 0 in this case
765- calling SCIPsolveConcurrent() when SCIP was compiled without a TPI now results in a plugin-not-found error
766- fixed LPI status functions of lpi_cpx if the barrier is called
767- check cuts for redundancy after scaling in cutTightenCoefs() and cutTightenCoefsQuad() of cuts.c
768- maintain definition of artificial integral variables in xor constraints to avoid invalidation of conflict constraints
769- free childless nodes only after the deactivation of the old focus path in treeSwitchPath() of tree.c
770- only normalize rows for column norm evaluations in shift-and-propagate heuristic to avoid unscaled violations
771- expression handler for absolute value computes now also a cut when one of the bounds is infinite as long as the sign of the argument is known
772- check for more data to be freed before modifying nonlinear constraints in SCIPaddExprNonlinear()
773- allow for terms with zero coefficients when checking sum in SCIPexprCheckQuadratic()
774- do not abort writing of constraints to lp/pip files (and forget to free buffer memory) when encountering unsupported nonlinear constraint
775- fixed that strings with names and descriptions of the LPI's were not null-terminated
776- fixed decision on when to enforce nonlinear constraints on relaxation solutions if integer variables are present
777- fixed reading of very long lines (>78000 characters) in FlatZinc reader
778- fixed write of strings with at least 1024 characters when compiling with MSVS 2015 (14.0) or later (still an issue with earlier MSVS, which will not be fixed)
779- keep epsilon coefficients in applyFixings() of cons_linear.c until multiples are merged to avoid loss of relevant contributions
780- fixed that some variable type changes were not accounted correctly in presolve of linear constraints
781- fix constraint sorting in setpp-orbitope upgrade in symmetry code
782- fixed that SCIPnodeGetConsProps() also counted bound changes from propagators
783- use original and-constraints of an untransformed pseudoboolean constraint when copying original problems to avert segmentation faults
784- sort and-constraints of a pseudoboolean constraint with respect to the resultant problem indices to avoid shuffled copies
785- treat pseudoboolean constraints as nonlinear constraints in OPB reader to prevent duplication mistakes
786
787Examples and applications
788-------------------------
789
790- in example Binpacking implement Farkas pricing for packings because branching can actually lead to infeasible restricted master LPs
791
792Testing
793-------
794
795- allow unknown parameters to let tests pass if only optional dependencies are missing
796
797Build system
798------------
799
800### Cmake
801
802- fixed compilation and linking with HiGHS; to use HiGHS, cmake now requires to specify the directory containing the `highs-config.cmake` file via `-DHIGHS_DIR`
803- extended identification of Ipopt library on Windows to also look for ipopt.dll.lib, as this is used since Ipopt 3.13.0 (2019)
804
805
806@section RN910 SCIP 9.1.0
807*************************
808
809Features
810--------
811
812- added constraint handler that checks and enforces bounds on original variables which have been fixed or aggregated in the transformed problem
813- allow for implicit integer variables in xor constraints
814- implemented symmetry detection callbacks for pseudoboolean constraints
815- added option to consider enforcement of nonlinear constraints (including spatial branching) before integrality has been enforced
816
817Fixed bugs
818----------
819
820- make sure that, in dual proof analysis, upgraded constraints can report their number of variables
821- check knapsack constraints as linear constraints to avoid violations based on implicit integrality
822- make sure that symmetry detection callbacks report success
823- make arithmetics in cuts.c more robust to avoid invalid scg cuts due to numerical rounding sensitivity
824- allow to copy pseudoboolean constraints even if no AND constraints are present in order to avoid a warning
825- set value for variable that is introduced to reformulate nonlinear objective function when reading .nl files with initial solution
826- fixed that multi-aggregations from PaPILO were accepted without ensuring that their bounds hold
827
828Examples and applications
829-------------------------
830
831- TSP: removed `gzstream.h/hpp` and parse gzipped files differently
832
833Interface changes
834-----------------
835
836### New callbacks
837
838- SCIP_DECL_NLHDLRENFO takes additional parameter branchcandonly to indicate whether only branching candidates should be registered,
839 without looking for cuts or boundchanges
840
841### New API functions
842
843- new function SCIPgetExprActivityNonlinear() to get activity of nonlinear constraint
844- new function SCIPincludeConshdlrFixedvar() to include new constraint handler that checks bounds on fixed original variables
845
846### New parameters
847
848- limits/primal to terminate the solve as soon as the primal bound is at least as good as this value, same as limits/objectivestop (deprecated)
849- limits/dual to terminate the solve as soon as the dual bound is at least as good as this value
850- presolving/milp/internalmaxrounds to control the maximal rounds for each call of the milp presolver (PaPILO)
851- constraints/fixedvar/∗ to control the new constraint handler that checks bounds on fixed original variables
852- constraints/nonlinear/branching/mixfractional to specify minimal average pseudo cost count for discrete variables
853 at which to start considering spatial branching before branching on fractional integer variables
854 (default infinity means that integrality is always enforced before nonlinear constraints)
855- constraints/nonlinear/branching/fracweight to specify weight of fractionality of integer variables in spatial branching
856
857### New data structures
858
859- enum SCIP_Status has been extended by SCIP_STATUS_PRIMALLIMIT and SCIP_STATUS_DUALLIMIT to indicate termination at limits/primal and limits/dual respectively
860
861Build system
862------------
863- changed the default symmetry computation package from sassy+bliss to sassy+nauty
864- bliss source is no longer included in the source tree, but can be linked as external library (https://github.com/ds4dm/Bliss)
865- cmake now automatically downloads and installs the latest release version of SoPlex from GitHub if it is not found directly
866
867Miscellaneous
868-------------
869
870- updated nauty to version 2.8.8
871
872
873@section RN901 SCIP 9.0.1
874*************************
875
876Fixed bugs
877----------
878
879- fixed bug in detection of double lex matrices due to wrong memory allocation
880- fixed bug where parameter `limits/objectivestop` was copied to subscips in plugins which have different objectives
881- in count mode respect empty solution when problem is solved in presolving
882- fixed that SCIP may have tried to pass a negative random seed to an LP solver
883- fixed bug where conflict analysis in strong branching tried to analyze an unsuccessful LP solve
884- enable parameter limits/restarts by allowing to reach the restart limit in restartAllowed()
885- handle normalizing linear constraints in presolving with more caution to avoid numerical difficulties for integer variables with large coefficients
886- use quad precision to calculate residual activity bounds to reduce numerical errors for large variable bounds in cons_linear.c
887- in SCIPsolveProbingLP() when objective has been changed do not return cutoff due to exceeding the cutoff bound
888- set probing LP to be a relaxation only when objective has not been changed
889- declare contradicting infinities in getMinActivity() and getMaxActivity() as non-tight
890- reject farkas solution with large values to bound magnification of errors in SCIPgetFarkasProof()
891- if all variables are fixed, apply relative feasibility tolerance to avoid invalid infeasibility in applyFixings() of cons_linear.c
892- delete empty redundant knapsack and linear constraints after cleanup in SCIPmatrixCreate()
893- cleanup first constraints in SCIPcleanupConssVarbound(), SCIPcleanupConssSetppc(), and SCIPcleanupConssLogicor()
894- symmetry handling methods have not been added immediately after computing symmetries, which has been fixed
895- delay checking node limits after presolving to correctly continue up to the exceeding main node
896- simplified the objective sense assumption for the subproblems in the Lagromory separator
897- update effective root depth iteratively to avoid trapping it at a single child node
898- fixed that dualsparsify presolver did not always check do-not-multiaggregate variable flag
899- fixed bug in computing elements of orbits in orbital reduction
900
901Miscellaneous
902-------------
903
904- redefine isrelax to istight in cons_linear.c
905
906Build system
907------------
908
909### Cmake
910
911- A file cmake.log containing the changed options is written to the cmake build directory.
912- removed replacement of the settings of RelWithDebInfo
913- add compile option -ffp-contract=off or /fp:precise to enhance reproducibility across different systems
914
915### Makefile
916
917- add flags -ffp-contract=off and /fp:precise to enhance reproducibility across different systems
918
919Interface changes
920-----------------
921
922### New parameters
923
924- added parameter "propagating/symmetry/symtiming" to determine when symmetries are computed and handled
925
926### Changed parameters
927
928- Disabled "propagating/symmetry/addconsstiming" since it is not used anymore.
929- Disabled "propagating/symmetry/ofsymcomptiming" since it is not used anymore.
930
931@section RN900 SCIP 9.0.0
932*************************
933
934Features
935--------
936
937- added simplification of abs(x)^n to x^n when n is even (simplify rule POW12)
938- in expression simplification, added possibility to expand power of sum with exponents larger than 2 (simplify rule POW7)
939- in expression simplification, added possibility to expand products with sums as factor when there are more than two factors (simplify rule SP12b)
940- in expression simplification, added possibility to allow expanding power of products with fractional exponent (simplify rule POW5a)
941- can now build with Lapack (used for solving nonlinear problems) explicitly; if IPOPT is used, then Lapack is accessed through it;
942 an interface to Lapack is available in lapack_calls.h
943- added support for logical constraints in binary variables and basic logical operators (and, or, not, equal) to AMPL .nl reader
944- indicator constraints now use the same slack variable for the linear constraints if binary variables are used multiple times
945 for indicator constraints
946- new diving heuristic indicatordiving that focuses on indicator variables which control semicontinuous variables
947- updated statistics on NLP relaxation; information on convexity of NLP has been added
948- added new bandit method (EXP.3-IX) that is the new default of the ALNS heuristic
949- added dialog to display recognized permutation symmetries ("display symmetry")
950- The symmetry detection code has been completely restructured. Instead of completely encoding symmetry information in
951 prop_symmetry.c, there is a new callback for constraint handlers, which returns symmetry relevant information by
952 encoding a constraint as a node and edge colored graph. This way, also custom constraint handlers can provide
953 symmetry information.
954- added special presolving step for logicor and set covering/packing for constraints with two variables and one independent variable
955- increased the depth field of the tree structure from 16 to 30 bits and the max depth of the search tree from 65534 to 1073741822
956- added new cut selector plugin called cutsel_ensemble. Performs a superset of hybrid cutsel. Implements new filtering methods and scoring options.
957- added new branching rule based on Gomory mixed-integer cuts
958- added new branching score to the reliability pseudo-cost branching rule
959- added new cut selector plugin called cutsel_dynamic. Performs a superset of hybrid cutsel. Implements new filtering methods and scoring options.
960- added monoidal strengthening to intersection cut generation of nlhdlr_quadratic
961- extended heuristic dps to run after processing the node and to use strict limits for the reoptimization step
962- extended obbt propagator to handle variables of the linear constraints corresponding to indicator constraints
963- added new heuristic heur_scheduler that models the selection of LNS and diving heuristics as a multi-armed bandit problem
964- added nonlinear handler for signomial expressions: adds cuts based on a difference of convex functions representation
965- Delayed separators are now called if no other cuts have been found. Previously, such separators were only called near stalling or when the separation rounds limit was reached.
966- added a new separator sepa_lagromory to generate Lagromory cuts in a relax-and-cut framework, i.e., GMI cuts generated
967 at different bases that are explored in the process of solving the Lagrangian dual problem at a node. This separator
968 is OFF by default.
969- when parsing nonlinear constraints from CIP files, the * after the number in a term is now optional if followed by a variable,
970 i.e., instead of 3*<x>*<y>, now also 3<x>*<y> can be read, but 3<x><y> is not supported;
971 this allows to read some CIP files that were written with SCIP < 8
972- when running bliss, we now limit the number of actually created generators and not the ones considered by bliss
973
974Performance improvements
975------------------------
976
977- Variable conflict-based addition of Schreier-Sims cuts for symmetry handling in prop_symmetry.c does no longer use
978 an expensive explicit conflict graph construction.
979- Only run propagation of indicator constraints if relevant variables have changed.
980- Propagation of indicator constraints propagates maximal activity of linear constraint to upper bound of slack variable.
981- Added initialization of LP relaxation for SOC constraints.
982- Avoided some numerical issues when separating SOC constraints.
983- If differentation of convex expression fails in convex nlhdlr, then a perturbed point is tried.
984- Use sassy/bliss as default symmetry computation package.
985- No longer linearize indicator constraints in undercover heuristic by default.
986- Deactivate pre-root heuristic zeroobj in undercover heuristic.
987- Added new branching score tiebreaker for reliability pseudo-cost branching rule
988- Try nearest bound if zero solution value is out of bounds in heuristic trivial.
989
990Interface changes
991-----------------
992
993### New and changed callbacks
994
995- Added solution linearization callback for nonlinear handlers.
996 The nonlinear handler may use this callback to add tight cuts that use the given solution as reference point to the cutpool.
997 The callback is called if option constraints/nonlinear/linearizeheursol is enabled.
998- The callback for copying problem data SCIP_DECL_PROBCOPY() now has a parameter "original" indicating whether the original
999 or transformed problem should be copied. Similarly, SCIPprobCopy() in prob.h/c has such a parameter.
1000- Added CONSGETPERMSYMGRAPH and CONSGETSIGNEDPERMSYMGRAPH callback for constraint handlers, which provides symmetry information about constraints to SCIP.
1001
1002### Deleted and changed API functions
1003
1004- SCIPtpiInitLock(), SCIPtpiDestroyLock(), SCIPtpiInitCondition(), SCIPtpiDestroyCondition() now take a double
1005 pointer to SCIP_LOCK/SCIP_CONDITION, respectively.
1006- Renamed SCIPtpiSumbitJob() to SCIPtpiSubmitJob().
1007- SCIPcreateConsIndicatorLinCons(), SCIPcreateConsIndicatorGenericLinCons() do not allow binvar to be NULL anymore
1008- Replaced SCIPnlrowSetCurvature() by SCIPsetNlRowCurvature().
1009- SCIPsnprintf() now returns the required string length in case reallocation is necessary.
1010- SCIPcomputeCoverUndercover() receives three more arguments which nonlinearities to cover
1011- removed definition of SQRT
1012- SCIPincludeObjConshdlr(), SCIPincludeConshdlr(), SCIPconshdlrCreate() receive two more arguments for the
1013 conshdlr callbacks CONSGETPERMSYMGRAPH and CONSGETSIGNEDPERMSYMGRAPH
1015- new parameter issigned for SCIPcomputeOrbitsSym()
1016- new parameter symtype for SCIPcomputeComponentsSym()
1017- new parameter symtype and permvardomaincenter for SCIPlexicographicReductionAddPermutation()
1018- replaced parameters matrixdata and exprdata of SYMcomputeSymmetryGenerators() by graph
1019
1020### New API functions
1021
1022- new functions for interfacing with Lapack: SCIPlapackIsAvailable(), SCIPlapackIsAvailable(), SCIPlapackComputeEigenvalues(), and SCIPlapackSolveLinearEquations
1023 These functions should be used instead of SCIPisIpoptAvailableIpopt(), SCIPcallLapackDsyevIpopt(), and
1024 SCIPsolveLinearEquationsIpopt() in the context of computing eigenvalues or solving linear equations.
1025 If IPOPT is available, the calls will be passed on to Ipopt's interface to Lapack.
1048- SCIPincludeCutselEnsemble(), SCIPselectCutsEnsemble() to include cutsel_ensemble or use the selection algorithm
1049- SCIPincludeBranchruleGomory() includes new gomory cut based branching rule
1050- SCIPgetVarAvgGMIScore(), SCIPincVarGMISumScore(), SCIPgetVarLastGMIScore(), SCIPsetVarLastGMIScore() set historical values used by SCIP's default branching rule
1051- SCIPincludeNlhdlrSignomial() includes the signomial nonlinear handler
1052- SCIPgetExprMonomialData() returns a monomial representation of a product expression
1053- SCIPestimateRoot() computes estimators for roots with exponent in [0,1]
1054- SCIPincludeCutselDynamic(), SCIPselectCutsDynamic() to include cutsel_dynamic or use the selection algorithm
1055- SCIPincludeSepaLagromory() to include the new Lagromory separator
1056- SCIPconsCompCheck() to compare two constraints based on their check priority
1057- SCIPgetConsPermsymGraph() and SCIPgetConsSignedPermsymGraph() to access the (signed) permutation symmetry detection graph of a constraint
1058- SCIPsetConshdlrGetPermsymGraph() and SCIPsetConshdlrGetSignedPermsymGraph() to set the (signed) permutation symmetry detection graph of a constraint
1059- SCIPconshdlrSupportsPermsymDetection() and SCIPconshdlrSupportsSignedPermsymDetection() to access whether a conshdlr supports detection of (signed) permutation symmetries
1060- new API functions for creating and manipulating a symmetry detection graph: SCIPcreateSymgraph(), SCIPfreeSymgraph(), SCIPcopySymgraph(), SCIPextendPermsymDetectionGraphLinear(),
1092 String values should not be quoted and spaces in string values are not supported.
1093- sassy can be used now as preprocessor for nauty/traces
1094- The solution status codes written to AMPL solution files now match those from https://mp.ampl.com/details.html#_CPPv4N2mp3sol6StatusE.
1095
1096### Changed parameters
1097
1098- change default value of parameter separating/filtercutpoolrel to FALSE
1099- Shrunk range of parameter "propagating/symmetry/sstleaderrule" from [0,3] to [0,2], removed "MAXCONFLICTS"-option.
1100- Removed reading/gmsreader/freeints. A default upper bound of +inf is now assumed for integer variables in GAMS (which is the case since GAMS 23.1).
1101- Disabled "propagating/symmetry/symfixnonbinaryvars" since it is not used in the new symmetry code.
1102- Replaced "propagating/symmetry/onlybinarysymmetry" with "propagating/symmetry/enforcecomputesymmetry" and set to FALSE by default.
1103- Disabled "propagating/symmetry/performpresolving" since running orbital reduction during presolving is not effective.
1104- Repurposed "propagating/symmetry/usedynamicprop" since it now also applies to lexicographic reduction.
1105- Changed default value of parameter "propagating/symmetry/addsymresacks" from FALSE to TRUE.
1106
1107### New parameters
1108
1109- separating/maxcutsgenfactor and separating/maxcutsrootgenfactor as factors (w.r.t. separating/maxcuts and
1110 separating/maxcutsroot) for limits on the number of cuts generated (which used to be constants '2')
1111- expr/pow/expandmaxexponent to specify limit on exponent when to expand power of sum
1112- expr/pow/distribfracexponent to enable expanding power of products with fractional exponents
1113- expr/product/expandalways to enable expanding any product with sums as factor (that is, also when more than two factors)
1114- nlhdlr/convex/maxperturb to specify maximal perturbation of non-differential reference points
1115- benders/default/nlpiterlimit to adjust iteration limit for NLP solver for Benders' decomposition NLP subproblems
1116- limits/objectivestop to interrupt the solve as soon as a primal solution is found
1117 that is at least as good as the given value
1118- heuristics/undercover/{coverand,coverind,covernl} to control which nonlinearities to consider (by default only "and" and nonlinear constraints)
1119- cutselection/ensemble/∗ all parameters for new ensemble cut selector
1120- cutselection/dynamic/∗ all parameters for new dynamic cut selector
1121- branching/relpscost/gmiavgeffweight specifies the weight in the relpscost branching score of the normalized efficacy of all generated GMI cuts (for a variable)
1122 branching/relpscost/gmilasteffweight specifies the weight in the elpscost branching score of the normalized efficacy of the last generated GMI cut (for a variable)
1123- nlhdlr/quadratic/usemonoidal to enable monoidal strengthening when separating quadratics with intersection cuts
1124- nlhdlr/quadratic/trackmore to collect more statistics for monoidal strengthening when separating quadratics with intersection cuts
1125- nlhdlr/quadratic/useminrep to use the minimal representation to compute cut coefficients when separating quadratics with intersection cuts
1126- nlhdlr/quadratic/sparsifycuts to enable sparsification of intersection cuts for quadratics
1127- heuristics/dps/reoptlimits to set strict limits for the reoptimization step in dps
1128- heuristics/dps/timing to run dps after processing the node
1129- heuristics/scheduler/∗ all parameters for new scheduler heuristic
1130- nlhdlr/signomial/enabled, nlhdlr/signomial/maxnundervars, nlhdlr/signomial/mincutscale: parameters for the signomial nonlinear handler
1131- separating/lagromory/freq to denote the frequency for calling Lagromory separator
1132- separating/lagromory/away to denote the minimal integrality violation of a basis variable to try separation
1133- separating/lagromory/dynamiccuts to denote whether the generated cuts be removed from LP if they are no longer tight
1134- separating/lagromory/maxroundsroot to denote the maximal number of separation rounds in the root node
1135- separating/lagromory/maxrounds to denote the maximal number of separation rounds in a non-root node
1136- separating/lagromory/nmaxcutsperlproot to denote, in the root node, the maximal number of Lagromory cuts that can be
1137 separated per explored basis of the Lagrangian dual
1138- separating/lagromory/nmaxcutsperlp to denote, in a non-root node, the maximal number of Lagromory cuts that can be
1139 separated per explored basis of the Lagrangian dual
1140- separating/lagromory/perroundnmaxlpiters to denote the maximal number of separating LP iterations that are allowed per
1141 separation round
1142- separating/lagromory/dualdegeneracyratethreshold to denote the minimum dual degeneracy rate for the separator execution
1143- separating/lagromory/varconsratiothreshold to denote the minimum variable-constraint ratio on the optimal face for the
1144 separator execution
1145- many other advanced parameters for the Lagromory separator, which are also mentioned under separating/lagromory/∗
1146
1147### Data structures
1148
1149- new data structure SYM_GRAPH to encode symmetry information from a constraint
1150- new data structure SYM_EXPRDATA to encode symmetry information from expressions
1151- replaced enum SYM_SYMTYPE by a complete new one; removed SYM_RHSSENSE, added SYM_NODETYPE and SYM_CONSOPTYPE
1152
1153Deleted files
1154-------------
1155
1156- deleted the now unused files: tpi_none.h, tpi_openmp.h, tpi_tnycthrd.h, type_tpi_none.h, type_tpi_openmp.h, type_tpi_tnycthrd.h
1157
1158Unit tests
1159----------
1160
1161- new unittests for nlhdlr_quadratic that test monoidal strengthening and the use of the minimal representation to compute cut coefficients
1162- unittests for nlhdlr_signomial
1163
1164Testing
1165-------
1166
1167- changed `set lim obj` to `set lim objective` in ctest since `obj` is no longer unambiguous
1168
1169Build system
1170------------
1171
1172### Cmake
1173
1174- New flag -DLAPACK=on for linking with Lapack (must be available in the system)
1175- added flag option "SYM=sbliss" for using sassy/bliss as a graph automorphism package
1176- use SYM=sbliss by default, since sassy and bliss are now shipped with SCIP.
1177- added flag option "SYM=snauty" for using sassy/nauty as a graph automorphism package
1178
1179### Makefile
1180
1181- added flag option "nauty" for SYM variable to specify which graph automorphism package should be used
1182- added flag option "sbliss" (sassy/bliss) for SYM variable to specify which graph automorphism package should be used
1183- added flag option "snauty" (sassy/nauty) for SYM variable to specify which graph automorphism package should be used
1184- use SYM=sbliss by default, since sassy and bliss are now shipped with SCIP
1185- New flag LAPACK for linking with Lapack (must be available in the system)
1186- A file scip/config.h is created in the build directory ($(OBJDIR)/include) now.
1187 Defining NO_CONFIG_HEADER is no longer necessary and has no effect anymore.
1188
1189Fixed bugs
1190----------
1191
1192- Number of runs in which separation is enabled will now be correct as per "separating/maxruns" parameter. Earlier,
1193 separation was enabled for "maxruns + 1" number of runs, i.e., separation was enabled even when "maxruns = 0" was set.
1194- add safeguard for number of selected cuts
1195- use double double precision for delta in activity updates of cons_linear.c
1196- sort constraints in checkSolOrig() to keep the logic of constraint handlers intact
1197- fixed make install when SHARED=no and make uninstall
1198- check absolute coefficients relative to extremal average to avoid invalid unifications in normalizeCons()
1199- enforce and check symmetry-based constraints to take their locks (in dual reductions) into account
1200- flush changes at the end of SCIPlpiSetBase() in lpi_grb.c to apply the newly set basis correctly
1201
1202Miscellaneous
1203-------------
1204
1205- The TPI has been changed to become mostly independent from the actual parallel interface during compile time.
1206 For this, the locks and conditions are now pointers to abstract structs.
1207- fixed that scip/def.h, the header for C preprocessor definition (`#define`'s), included headers for some SCIP type and function definitions
1219- fixed that scaling of rows in Gurobi interface (SCIPlpiScaleRow()) changed infinite sides to large finite ones (1e20) when scale factor is negative
1220- check whether objective limit is truly reached in SCIPlpiIsStable()
1221- if an objective limit is set and Mosek claims that it is exceeded, check that this is indeed the case in SCIPlpiIsStable()
1222- the .mps file reader was extended to additionally accept .mps files with the objective sense section on one line
1223- ensure that delayed cutpool separation does not happen if enough cuts have been found already
1224- fixed that a Gurobi or Mosek interface (LPI) could not be freed from a thread different than the one it was created in, which lead to problems when, e.g., using the concurrent optimizer
1225- in cons_varbound if both variables are fixed, instead of propagating the constraint check the feasibility of the constraint since propagating can lead to unnecessary numerical troubles
1226- fixed memory leak in branching rule "distribution"
1227- fixed that undercover did not enforce that sufficiently many variables in an and-constraints were fixed to have it linearized in the generated sub-scip
1228- fixed two bugs in cons_varbound: avoid adding variable bounds if vbdcoef is infinite and unlock/lock variables if lhs/rhs/vbdcoef are changed
1229- globalize constraint changes before bound changes during the effective root shift in treeSwitchPath() to correctly update variable locks by avoiding global bounds with outstanding bound change events when deleting constraints
1230- fixed error when attempting to copy SCIP with activated pricers
1231- remove integrality check for implicit integral variables in cons_integral.c, updated the definition for variable type implicit integer to be more explicit that these variables can take fractional values, and updated FAQ entry
1232- updated and, or, and pseudoboolean constraint handlers to better handle fractional implicit integer variables in enforcement
1233- avoid invalid strong Chvatal-Gomory cuts by ceiling with tolerance in the calculation of parameter k and flooring slack coefficients with standard epsilon tolerance as well as quad precision
1234- add missing row links to columns in SCIPflushRowExtensions() required to maintain correct row norms
1235- restrict separator intobj to solutions for which there can be no better feasible integral objective values to avoid cutting them off
1236- delay removal of clique lists from SCIPvarRemoveCliquesImplicsVbs() into cliqueCleanup() to avoid segmentation faults by incomplete cleanups after variable conversions
1237- reject sub-solutions with invalid objectives in SCIPtranslateSubSols() due to contradicting infinite contributions
1238- correct column index in getMinMaxActivityResiduals() to make presolver dualinfer work
1239- copy quiet flag from main scip's message handler to the one of solverscip in concurrent optimization
1240- avoid bound tightening cycles towards huge redundancy bounds in fullDualPresolve() to avert fatal numerical trouble in representing vertices of linear relaxations with unbounded domains
1241- fix problem where debug solution did not work if branching constraints are present
1242- update index of dominating variable on coefficient deletion in dualPresolving() of constraint handler logicor
1243- pass on flags from a redundant to the implying varbound constraint in preprocessConstraintPairs() to avoid suboptimal fixings by model relaxations
1244- apply reductions of dualinfer only if a dual solution exists (primal is bounded)
1245- before presolving is finished check solutions before retransforming them including tiny values to keep check flags consistent
1246- disable heuristics before and during presolving in benders decomposition to avoid messing up the objective structure in the solution store by dropping auxiliary variables in the required retransformations
1247- correct local flag of singleton conflict constraints in tightenSingleVar() against invalid bound globalization
1248- respect unboundedness in the computation of activity bounds in conflict.c to avoid invalid huge bounds due to small coefficients on unbounded variables
1249- ensure positive sides of a linear constraint when recognizing a set partition in rangedRowSimplify() to account for redundancy issues
1250- relax numerical conditions for variable aggregations to avert invalid variable fixings
1251- fixed harmless read of uninitialized data when creating parameters
1252- fix call of SCIPnlpiOraclePrintProblem in nlpi_worhp
1253
1254Performance improvements
1255------------------------
1256
1257- Use sassy/bliss as default symmetry computation package.
1258
1259Interface changes
1260-----------------
1261
1262### Interfaces to external software
1263
1264- added interface to nauty/traces for symmetry computation
1265- added interface to sassy, a preprocessor for symmetry computation
1266- The directory src/sassy contains the source code of sassy.
1267
1268Build system
1269------------
1270
1271### Cmake
1272
1273- added flag option "SYM=sbliss" for using sassy/bliss as a graph automorphism package
1274
1275### Makefile
1276
1277- added flag option "nauty" for SYM variable to specify which graph automorphism package should be used
1278- added flag option "sbliss" for SYM variable to specify which graph automorphism package should be used
1279- use SYM=sbliss by default, since sassy and bliss are now shipped with SCIP
1280
1281Miscellaneous
1282-------------
1283
1284- the parameter change callback is no longer called at the moment a parameter is created
1285
1286@section RN804 SCIP 8.0.4
1287*************************
1288
1289Features
1290--------
1291
1292- use quad precision in cutsSubstituteMIR() for substituting slack variables into CMIR cuts
1293- use quad precision for activity computations in cons_linear.c
1294
1295### Deleted and changed API functions
1296
1297- SCIPshrinkDisjunctiveVarSet() no longer attempts to cutoff the current node if it finds the
1298 given disjunction to be infeasible; it is now in the responsibility of the caller to act accordingly
1299
1300### New API functions
1301
1302- added SCIPskipSpace
1303- added XML parser routines from src/xml/xml.h
1304
1305### Interfaces to external software
1306
1307- updated XPRESS interface to work with XPRESS 41 as well
1308- new interface to LP solver HiGHS (lpi_highs.cpp)
1309
1310### Changed parameters
1311
1312- changed integer parameter "propagating/symmetry/recomputrestart" from range {0, 1, 2} to being fixed at value 0
1313
1314Unit tests
1315----------
1316
1317- added new checks for objective, bounds and sides inside the scaling tests in lpi/change.c
1318
1319Fixed bugs
1320----------
1321
1322- relax condition of assert in lpSolve to hold only if lp/checkstability is true
1323- OPB reader: dynamically increase the size of the line buffer for reading in getMaxAndConsDim()
1324- Enabled the solution limit checks in SCIPsolveIsStopped in solve.c when in SCIP_STAGE_PRESOLVING
1325- fix quad precision comparison for the calculation of knapsackcover constraints.
1326- force copying of symmetry constraints for concurrent solve
1327- increase the precision of double multiplications in quad precision environments
1328- corrected handling of different variable types in symmetry
1329- orbitope detection: refine computation of overlap structure and fixed bug in finding orbitope generators
1330- ensure that winner is always determined in concurrent mode
1331- when a row with invalid index range is added to the global cutpool, update the indices instead of failing with an assert
1332- update of watched literals in cons_xor.c and ensure that fixed variables are counted in propacateCons()
1333- avoid some numerical issue in check for redundant variables in linear constraints (introduced with version 8.0.2)
1334- more rows are treated as being integral in cutsSubstituteMIR() for CMIR cuts
1335- fixed several relaxations of the rhs of cuts to 0 in cuts.c
1336- avoid aggregation into a single linear constraint if they should not be upgraded (needed for indicator constraints)
1337- apply effective root changes before fork is repropagated during treeSwitchPath() in tree.c
1338- avoid invalid objective value for solutions generated from an unbounded LP relaxation in case of a nonlinear objective function
1339- disable recomputing symmetries after a restart (constraint removal is not permitted)
1340- avoid cutting off optimal solutions for small feasibility tolerances in conflict analysis
1341- initialize variable in presol_dualsparsify.c
1342- fix in presolving of variable bound constraints to use absolute instead of relative difference
1343- free variable histories in reoptimization mode
1344- handle whitespaces in interactive shell history consistently
1345- check and enforce equalities on which the objective is projected in cons_linear.c
1346- ensure row feasibilities of solution shiftings in heur_oneopt.c and heur_twoopt.c
1433- new parameters to turn on more statistics: misc/showdivingstats (diving heuristics), heuristics/alns/shownbstats (ALNS), estimation/showstats (tree size estimation)
1434
1435### Data structures
1436
1437- added nrootcalls and ncutsadded to SCIP_Cutpool
1438- added fromcutpool flag to SCIP_Row and fixed 33 bit allocation
1589 Removed support for parameterized expressions.
1590- Added support for expression types sin, cos, and entropy. Added an expression type that stores a SCIP variable.
1591- Added handling of sin and cos expressions in OSiL reader.
1592- Added handling of sin, cos, and tan expressions in ZIMPL reader.
1593- Added expression handler plugin type, removed user expression type.
1594- Replaced expressions, expression trees, and expression graphs by a new implementation of expressions.
1595- Added differentiation methods (Gradients and Hessian directions) to expressions.
1596- Added integrality information to expressions.
1597- Added comparison and hashing of expressions.
1598- Improved simplification of expressions and identification of common subexpressions, in particular terms that appear
1599 equally in several quadratic functions are now identified.
1600- Expression simplification now expands powers also when the resulting exponents will be larger than 2.
1601- Added table to print statistics on expression handlers.
1602- Removed interval-arithmetic evaluation from expression interpreter (interfaces to automatic differentiation codes).
1603- Hessians for user-provided expression handlers are not available in the NLP solver interfaces for now.
1604- Sparse Hessians are now returned by expression interpreter. Removed dense Hessians.
1605
1606Constraint handlers for NLP:
1607- cons_nonlinear has been completely rewritten and now handles constraints of the form lhs <= expr <= rhs, where
1608 expr is an expression using the new expression type. A linear part of a nonlinear constraint is no longer distinguished.
1609- Methods that work on a particular nonlinear structure are now implemented via nonlinear handlers (nlhdlr).
1610 These handlers are plugins of cons_nonlinear and interact with cons_nonlinear by detecting structures in expressions and
1611 providing propagation and separation mechanisms.
1612- Added nlhdlr "default" as a mandatory nlhdlr: this is a nlhdlr that gets active on expressions that no other nlhdlr handles.
1613 It then uses the callbacks implemented in expression handlers to provide domain propagation and linear under/overestimates.
1614- Added nlhdlr for quadratic expressions: domain propagation that was previously part of cons_quadratic; separation via intersection cuts (currently disabled).
1615- Added nlhdlr for bilinear expressions: collects bilinear products and provides under/overestimation of a product over a 2D-projection of the LP.
1616- Added nlhdlr for convex and concave expressions: detection of convex/concave subexpressions and linear under/overestimation.
1617- Added nlhdlr for quotients: detects quotients, provides specialized linear under/overestimation and domain propagation for univariate quotients.
1618- Added nlhdlr for perspective reformulations: detects expressions in semi-continuous variables and tightens linear
1619 under/overestimates of these expressions by applying a perspective transformation.
1620- Added nlhdlr for second-order cones: detects second-order cone constraints (as ||x|| <= t or a quadratic that can written like that) and
1621 separates on a disaggregated reformulation (similar to cons_soc previously).
1622- Removed constraint handlers abspower, bivariate, quadratic, and soc.
1623- Removed simplification of duplicate abspower constraints for now.
1624 Removed simplification of abspower constraints with loose variables.
1625 Removed resolving of domain propagation (ConsResProp callback) and conflict analysis for abspower constraints.
1626 Removed propagation of varbounds for variables of abspower constraints.
1627 Removed reformulation of abs(x)^p * x into signpower expression for now.
1628- Removed reformulation of SOC constraints when adding to the NLP.
1629 Removed possibility to add linearizations a la Glineur or BenTal&Nemirovski for SOC constraints.
1630- Removed possibility to disaggregate quadratic constraints.
1631 Removed lifted tangent inequalities for bilinear terms in quadratic constraints.
1632 Removed option to project LP solution onto feasible region of a quadratic constraint via interior point or gauge function.
1633 Removed handling of unbounded LPs when enforcing quadratic constraints.
1634- Removed construction of cuts from interval gradients for nonlinear constraints.
1635 Removed possibility to pretend that all nonlinear constraints are convex.
1636 Removed possibility to create local or non-initial nonlinear constraints for now.
1637- Removed explicit reformulation of nonlinear constraints in presolve.
1638 An extended formulation is now generated implicitly and used to construct the LP relaxation,
1639 but the original formulation is used to check feasibility, propagate variable domains, etc.
1640 Variables that are added for the extended formulation are now marked as relaxation-only.
1641- Improved locking of nonlinear variables in nonlinear constraints by taking monotonicity into account.
1642- Improved mechanisms to detect and handle structures in nonlinear constraints, which allows for several algorithms
1643 to work simultaneously on equal or overlapping expressions.
1644- Improved linearization of (sums of) products of binary variables, e.g., clique information is now taken into account.
1645 Removed option to linearize products between a binary and a non-binary variable.
1646- Nonlinear constraints with the same function (but possibly different left- or right-hand-side) are now merged.
1647- When a variable appears in only one concave less-or-equal constraint, it will be fixed to one of its bounds in more cases now.
1648- New branching rule for variables in nonlinear constraints (implemented in cons_nonlinear) that scores candidates
1649 based on constraint violation, variable type, and pseudo-costs simultaneously.
1650- Added tables to print statistics of nonlinear constraint handler and nonlinear handlers.
1651
1652Performance improvements
1653------------------------
1654
1655- Use the objective cutoff row as base row for separation in sepa_aggregation.c.
1656- Separate lifted cover cuts based on newer lifting function of Letchford and Souli (2019) in sepa_aggregation.c.
1657- In-tree restarts due to tree size estimation have been made compatible with orbital fixing.
1658- Improved upgrade of orbisacks to packing/partitioning orbitopes.
1659- Improved running time of symresack cover separation.
1660- Improved propagation algorithm for orbisack and symresack.
1661- Improved handling for expressions of type signpower in CppAD interface by making use of CppADs conditional expressions.
1662- Faster reevaluation of Hessian for quadratic expressions in CppAD interface.
1663- Enabled optimization of taped expressions in the CppAD interface.
1664- Sparse Hessian evaluation for expressions with sparse Hessian in the CppAD interface.
1665- Disabled branching on variables that are added for the extended formulation of a nonlinear constraint.
1666- Prefer branching on variables in nonconvex terms of nonlinear constraints also if a cut could be generated but would yield a small reduction in the convexification gap only.
1667- When violations of nonlinear constraints are tiny, the feasibility tolerance for the LP relaxation may now be reduced temporarily to allow for cuts to have an effect.
1668- Improved under/overestimation of multidimensional vertex-polyhedral (e.g., multilinear or concave) functions by use of scaling and keeping the cut-generating LP around.
1669- Products in nonlinear constraints are no longer disaggregated for the extended formulation.
1670- No longer relax bounds of integral variables when computing bounds on activity in nonlinear constraints.
1671- Revised and improved Ipopt interface.
1672- Revised and improved subNLP primal heuristic, in particular choice of iteration limit and starting condition and reuse of subSCIP.
1673- Merge strongcg into the gomory separator to avoid computing the same base equality twice. The files
1674 sepa_strongcg.{h|c} have been removed.
1675- The RENS neighborhood in ALNS now fixes fractional variables if necessary for reaching its target fixing rate.
1676- Use cpsolver emphasis in sepa_rapidlearning.
1677- If decomposition/maxgraphedge = 0, the computation of the block graph is completely turned off.
1678- Fixed a performance bug in cons_integral.c where rounding information was passed incorrectly to the generic diving algorithm.
1679
1680Examples and applications
1681-------------------------
1682
1683- Add c++ Sudoku example
1684- Removed circle.c and renamed string.c to spring.c in CallableLibrary example.
1685- SCIP-Jack (Steiner tree application):
1686 Most files have been modified and many new ones have been added (code base more than doubled).
1687 Two new problem classes are supported: maximum-weight connected subgraph problem with budget constraints, partial-terminal node-weighted Steiner tree problem.
1688 Major performance improvements accross all problem classes that are supported.
1689
1690Interface changes
1691-----------------
1692
1693### New and changed callbacks
1694
1695- extend SEPAEXEC{LP,SOL} callbacks by parameter "depth", which should be used within separation instead of SCIPgetCurrentDepth()
1696- extend SCIPseparateSolCutpool() by parameter "pretendroot", which is passed to SCIPcutpoolSeparate() instead of SCIPtreeGetCurrentDepth(scip->tree) == 0
1714- added SCIP_NLPIPROBLEM* problem to SCIP_DECL_NLPIGETSOLVERPOINTER
1715
1716### Deleted and changed API functions
1717
1718- When calling SCIPdelVar() in the SCIP_STAGE_PROBLEM stage, it is now documented as the user's responsibility to ensure
1719 the variable is not present in any constraints. Otherwise, SCIPsolve() now returns SCIP_INVALIDDATA.
1720- removed SCIPselectCuts(), replaced by SCIPselectCutsHybrid() of the hybrid cut selector plugin
1721- If SCIPvarMarkRelaxationOnly() is called for a variable, then this now need to happen before the
1722 variable is added to the transformed problem (SCIPaddVar()).
1723 SCIPvarMarkRelaxationOnly() will automatically call SCIPvarMarkDeletable().
1724- SCIPcomputeOrbitsFilterSym() and SCIPcomputeComponentsSym(): Type of argument componentblocked
1725 changed from SCIP_Shortbool* to unsigned*.
1726- removed SCIPsetParam()
1727- SCIPcreateConsOrbitope() and SCIPcreateConsBasicOrbitope() have two new arguments "usedynamicprop"
1728 and "mayinteract" to encode whether a dynamic reordering of the orbitope rows shall be used in
1729 full orbitope propagation and whether the orbitope might interact with other symmetry handling
1730 methods, respectively.
1731- internal function SCIPgetPropertiesPerm() has been replaced by SCIPisInvolutionPerm()
1732- internal function SCIPgenerateOrbitopeVarsMatrix() has new arguments "storelexorder", "lexorder",
1733 "nvarsorder", "maxnvarsorder" to compute and store the lexicographic order defined by an orbitope
1734- renamed SCIPcomputeArraysIntersection() and SCIPcomputeArraysSetminus() to
1735 SCIPcomputeArraysIntersectionInt() and SCIPcomputeArraysSetminusInt(), respectively, and changed
1736 their return type from SCIP_RETCODE (which _always_ was SCIP_OKAY) to void
1737- removed SCIPincludeDialogDefault(), use SCIPincludeDialogDefaultBasic() instead and check whether you also need SCIPincludeDialogDefaultSet() and SCIPincludeDialogDefaultFix()
1738- removed exprint argument from SCIPaddNlRowGradientBenderscutOpt()
1739- added copyexprhdlrs argument to SCIPcopyPlugins() (19th position)
1740- added copycutselectors argument to SCIPcopyPlugins() (10th position)
1741- removed refpoint argument from SCIPaddSquareSecant()
1742- added argument exprdata to SYMcomputeSymmetryGenerators()
1757- renamed SCIPsetNlRowExprtree() to SCIPsetNlRowExpr() and changed type of expr(tree) argument to SCIP_EXPR*
1758- SCIPenableNLP() is no longer allowed in stages INITSOLVE and SOLVING
1759- removed SCIPaddLinearConsToNlpHeurSubNlp()
1760- SCIPhasNLPSolution() now returns true also if a infeasible solution to the NLP exists; SCIPcreateNLPSol() can now also be used when only an infeasible solution to the NLP exists
1761- renamed SCIPsolveNLP() to SCIPsolveNLPParam() and added parameter SCIP_NLPPARAM param
1762- removed SCIPsolveDiveNLP(), use SCIPsolveNLPParam() instead
1810- removed SCIPnlpiOracleGetVarDegree() and SCIPnlpiOracleGetVarDegrees(), use SCIPnlpiOracleIsVarNonlinear() and SCIPnlpiOracleGetVarCounts(), respectively, instead
1811- removed SCIPnlpiOracleGetConstraintDegree(), use SCIPnlpiOracleIsConstraintNonlinear() instead
1812- removed argument messagehdlr from SCIPnlpiOraclePrintProblem() and SCIPnlpiOraclePrintProblemGams()
1813- removed SCIPcreateNlpiProb(), use SCIPcreateNlpiProblemFromNlRows() instead
1814- renamed SCIPupdateNlpiProb() to SCIPupdateNlpiProblem() and moved into scip_nlpi.{h,c}
1815- renamed SCIPaddNlpiProbRows() to SCIPaddNlpiProblemRows() and moved into scip_nlpi.{h,c}
1817- removed SCIPgetIpoptApplicationPointerIpopt(), use SCIPgetNlpiSolverPointer() instead
1818- removed SCIPnlpStatisticsCreate(), SCIPnlpStatisticsFree(), SCIPnlpStatisticsGetNIterations(), SCIPnlpStatisticsGetTotalTime(), SCIPnlpStatisticsSetNIterations(), SCIPnlpStatisticsSetTotalTime(), the struct is public now
1819- renamed LapackDsyev() to SCIPcallLapackDsyevIpopt()
1820- renamed SCIPsolveLinearProb() to SCIPsolveLinearEquationsIpopt()
1821
1822Expression interpreter:
1823- removed functions that operated with SCIPInterval
1824- changed first argument of SCIPexprintCreate() to SCIP*
1825- added SCIP* as first argument to SCIPexprintFree()
1826- added SCIP* as first argument to SCIPexprintCompile(), changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA**
1827- added arguments SCIP*, SCIP_EXPRINT*, and SCIP_EXPR* as first arguments to SCIPexprintFreeData()
1828- renamed SCIPexprintGetExprtreeCapability() to SCIPexprintGetExprCapability();
1829 added SCIP* as first argument, changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA*
1830- removed SCIPexprintNewParametrization()
1831- SCIPexprintEval(): added SCIP* as first argument, changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA*
1832- removed SCIPexprintEvalInt()
1833- SCIPexprintGrad(): added SCIP* as first argument, changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA*
1834- removed SCIPexprintGradInt()
1835- removed SCIPexprintHessianSparsityDense() and SCIPexprintHessianDense, use SCIPexprintHessianSparsity() and SCIPexprintHessian() instead
1836
1837Expressions:
1838- removed SCIPexpropGetName(), use SCIPexprhdlrGetName() instead
1839- removed SCIPexpropGetNChildren()
1840- removed SCIPexprGetOperator(), use SCIPexprGetHdlr() instead
1841- removed SCIPexprGetOpIndex(), SCIPexprGetOpReal(), SCIPexprGetOpData(), use SCIPexprGetData() instead
1842- removed SCIPexprGetRealPowerExponent(), SCIPexprGetIntPowerExponent(), SCIPexprGetSignPowerExponent(), use SCIPgetExponentExprPow() instead
1843- removed SCIPexprGetLinearCoefs(), SCIPexprGetLinearConstant(), use SCIPgetCoefsExprSum() and SCIPgetConstantExprSum() instead
1963- renamed SCIPgetNAllBilinearTermsQuadratic() to SCIPgetNBilinTermsNonlinear() and changed argument from SCIP* to SCIP_CONSHDLR*
1964- renamed SCIPgetAllBilinearTermsQuadratic() to SCIPgetBilinTermsNonlinear() and replaced arguments by SCIP_CONSHDLR* and changed return type to SCIP_CONSNONLINEAR_BILINTERM*
1965- removed SCIPaddBilinearIneqQuadratic(), use SCIPinsertBilinearTermImplicitNonlinear() instead
1966- renamed SCIPcreateConsQuadratic() to SCIPcreateConsQuadraticNonlinear() and removed argument stickingatnode
1967- removed SCIPincludeConshdlrSOC()
1968- replaced SCIPcreateConsBasicSOC() by SCIPcreateConsBasicSOCNonlinear()
1969- deprecated SCIPcreateConsSOC(), use SCIPcreateConsBasicSOCNonlinear() instead
1970- deprecated SCIPgetNlRowSOC(), use SCIPgetNlRowNonlinear() instead
2190- Removed parameters for strongcg separator: separating/strongcg/..., i.e.,
2191 maxrounds, maxroundsroot, maxsepacutsroot, maxsepacuts, dynamiccuts. One can control the
2192 strongcg behavior throught the parameters of sepa_gomory.
2193- renamed separating/{minortho,minorthoroot,objparalfac,intsupportfac} to cutselection/hybrid/{minortho,minorthoroot,objparalweight,intsupportweight}
2194
2195### New parameters
2196
2197- It is now possible to add orbitope constraints to handle symmetries even if not all variables
2198 in a component of the symmetry group are binary. This feature can be enabled using the
2257- new parameters "branching/inference/conflictprio" and "branching/inference/cutoffprio" that allow
2258 using the different score criteria in inference branching hierarchically
2259- new parameters "heuristics/alns/nodesquotmin", "heuristics/alns/maxcallssamesol" and "heuristics/alns/initduringroot"
2260 to control neighborhoods in ALNS
2261- new parameter "benders/default/benderscut/optimality/mir" to control whether mixed-integer rounding procedure is applied to Benders optimality cuts
2262- new parameter "misc/avoidmemout" to try to avoid running into memory limit
2378- added test projection:transitivity in prob/obbt.c
2379- added reader/nl.c
2380- added test intervalarith:sincos in scip/intervalarith.c
2381- added sepa/minor.c
2382- added sepa/rlt/cuts.c
2383- added sepa/rlt/product_detection.c
2384- added sepa/rlt/separation.c
2385- added tests test_compute_symmetry:expr{1,2,3,4} in symmetry/compute.c
2386
2387Build system
2388------------
2389
2390- the separate NLPI library has been integrated into the main SCIP library;
2391 uses of NLPILIBFILE or NLPILIBSRC in Makefiles that use make/make.project
2392 should be removed
2393
2394### Cmake
2395
2396- replace flag PARASCIP by THREADSAFE
2397- option AMPL is now ON by default
2398- add -D_XOPEN_SOURCE=600 cflag for compilation on systems other than windows
2399- add compile options directly instead of modifying CMAKE_C_FLAGS and CMAKE_CXX_FLAGS
2400
2401### Makefile
2402
2403- prefix PKG_CONFIG_PATH with Ipopt's pkgconfig dir instead of postfixing
2404- replace flag PARASCIP by THREADSAFE
2405- flag AMPL is now true by default
2406- libscip has been renamed to libscipbase and libscipsolver has been renamed to libscip
2407 in order to have the same library names for makefiles and cmake. For downward
2408 compatibility libscipsolver still exists (as a link).
2409
2410Fixed bugs
2411----------
2412
2413- fixed handling of multi-aggregation in cons_symresack and cons_orbisack
2414- SCIPgetLowerbound() now consistently returns infinity when status is infeasible
2415- improved the likelihood that a solution that satisfies the nonlinear constraints in the transformed (presolved) problem is also feasible for the original problem
2416- worked around a problem with derivatives of pow at 0 with non-integer exponents in CppAD
2417- fixed that setting of feasiblity and optimiality tolerance for NLP relaxation was overwritten with defaults when solving NLP
2418- fixed variance computation in t-value computation in hypothesis testing of reliability branching
2419- fixed potential overflow in cuts.c:evaluateLiftingFunctionKnapsack()
2420- do not transfer dual reductions to main SCIP in sepa_rapidlearning if strong dual reductions are forbidden
2421- fixed a bug in cons_setppc.c:removeDoubleAndSingletonsAndPerformDualpresolve() which led to wrong variable aggregations
2422- added missing redundancy check to coefficient tightening routine in cons_varbound that led to wrong variable locks
2423- added a check of numerics to avoid wrong reductions in cons_linear.c:simplifyInequalities()
2424- fixed a bug in cons_logicor.c regarding fixed variables that were not removed
2425- presol_milp.c handles variable fixings, suggested by PaPILO, more carefully to cover all cases that can appear
2426- fixed several reproducability bugs that led to different solving paths across multiple runs with one SCIP environment
2427- fixed check of limits/absgap, which was incorrectly applied to the scaled objective of the transformed problem
2428
2429Miscellaneous
2430-------------
2431
2432- in LP, use absolute instead of relative tolerances to check whether solutions from LP solver are primal feasible
2433- when a restart occurs, SCIP now asserts (during EXITSOLVE) that all relaxation-only variables are unlocked and
2434 only captured by the transformed problem.
2435- Avoid redundant calls to LP solver when LP is already flushed and solved
2436- In SCIPdebugMsg(), SCIPsetDebugMsg(), SCIPstatDebugMsg() strip directory from filename.
2437- Recompute activity of rows when checking LP solutions instead of trusting the value given by the LP solver
2438- The define NPARASCIP has been replaced by SCIP_THREADSAFE
2439- Parameters are not reset to their default values before activating an emphasis setting; this now allows to combine
2440 different emphasis settings.
2441- If a lazy bound is set to a value that is tighter than the current global bound, then the global bound is now tightened accordingly.
2442
2443@page RN7 Release notes for SCIP 7
2444
2445@section RN703 SCIP 7.0.3
2446*************************
2447
2448Interface changes
2449-----------------
2450
2451### New API functions
2452
2453- added function SCIPwithDebugSol() to determine whether SCIP was compiled with WITH_DEBUG_SOLUTION
2454
2455- New function SCIPcreateConsBounddisjunctionRedundant() and SCIPcreateConsBasicBounddisjunctionRedundant() that allow
2456 the input to contain redundant literals.
2457
2458### Changed API functions
2459
2460- added __attribute__((format(printf,,,))) to variadic SCIP message printing functions;
2461 this enables warnings about mismatches between format string and variadic function arguments if using GCC.
2462
2463### Interfaces to external software
2464
2465- removed MATLAB interface from interfaces/matlab
2466
2467Build system
2468------------
2469
2470- Compilation will now also work in a raw tarball of the scip git repository
2471
2472### Cmake
2473
2474- Make find_package more verbose and require packages to be found. Now enabled packages that are not found result in an error.
2475
2476Fixed bugs
2477----------
2478
2479- Fixed numerical bug by creating and checking the empty solution when problem vanishes in presolving.
2480- Fixed several bugs in reoptimization.
2481- Fixed bug in cons_bounddisjunction in which a constraint leads to a cutoff.
2482- Fixed bug in reoptimization by avoiding redundant literals for bound disjunctions.
2483- Replace wrong usage of CMAKE_BINARY_DIR by PROJECT_BINARY_DIR in CMake system
2484- Fixed lpi_glop to use absl flag instead of GFlags
2485- Fixed invalid initialization of limits/softtime parameter in cons_components
2486- Fixed MIN macro not defined in some cases.
2487- Safeguard some API functions for querying solving statistics against segmentation faults after SCIPpresolve()
2488- Fixed unfreed solution in concurrent solving
2489- Make sure that logicor constraints are enforced/separated if genlogicor is true in cons_indicator.
2490 Thus, do not change constraints/logicor/sepafreq anymore, but output warning.
2491- Fixed assert that assumed infeasibility cannot occur in presol_boundshift.
2492- Fixed sign bug during creation of conflict constraints with almost zero left-hand side.
2493- Disabled call of conflict handler for conflict sets that contain relaxation-only variables.
2494- Fixed bug in cons_symresack by initializing all constraint data in constrans
2495- Avoid allowing the upgrade of linear constraints corresponding to indicators in propagation of nodes.
2496- Fixed bug in computing lex. min/max faces in dynamic orbitope propagation.
2497- Limit vbounds propagator to one sweep through all bounds per call in order to avoid an infinite loop.
2498- Fixed mismatches between formatter strings and arguments in calls to SCIP message printing functions.
2499
2500Miscellaneous
2501-------------
2502
2503- To avoid performance variablity during reoptimization, the active constraints are now stored in the same order as in the
2504 original problem.
2505- Added workaround for bug in MSVS 2019 when compiling CppAD source.
2506- The original order of variables is now only restored after presolve if `randomization/permutevars` is set to FALSE.
2507
2508@section RN702 SCIP 7.0.2
2509*************************
2510
2511Features
2512--------
2513
2514- Extended check for valid variable and constraint names in PIP writer.
2515- Indicator constraints now write the name of the linear constraint in CIP format. This avoids a complicated
2516 name matching during parsing. The old format is still supported.
2517- The objective scale and offset are now taken into account when reading/writing problems in lp/mps/fzn/pip format.
2518 This often changes the behavior when writing transformed problems.
2519
2520Performance improvements
2521------------------------
2522
2523Examples and applications
2524-------------------------
2525
2526- Add c++ Sudoku example
2527
2528Interface changes
2529-----------------
2530
2531### Deleted and changed API functions
2532
2533- deprecated SCIPsetParam(); use SCIPsetIntParam(), SCIPsetRealParam(), etc, instead
2534
2535### New API functions
2536
2537- new function SCIPcolGetVarProbindex() for accessing the probindex of a variable corresponding to a column
2538- added new sorting functions SCIPsortPtrRealRealBoolBool()
2539
2540Fixed bugs
2541----------
2542
2543- Fixed a sign bug occuring for some cases in the computation of the directed cutoff distance
2544- Fixed overflow in inference information of cumulative constraint handler
2545- Fixed problem with propfreq == 0 in cons_linear.c
2546- Fixed aggregation heuristic in sepa_aggregation.c to not use local rows when that is requested nor modifiable rows
2547- Fixed problem with incompatibility of symmetry handling in Benders decomposition
2548- Fixed parsing of small number in CIP format of nonlinear constraint
2549- Fixed problem in upgrading full orbitopes to partitioning orbitopes
2550- Fixed treatment of negated variables in parsing orbitope constraints
2551- Fixed potential indexing error in prop_vbounds.c
2552- Fixed bug in writing fzn format
2553- Revert to old parameter value when parameter change is rejected in PARAMCHGD callback
2554- Fixed order of linker flags when building AMPL interface with cmake system.
2555- Fixed bug with ofsymcomptiming == 0: now symmetry is actually computed
2556- Improved separation for SOC constraint with multiaggregated variable on right-hand-side.
2557- Fixed bug in presol_boundshift: do not shift non-active variables
2558- Fixed bug in domain propagation for SOC constraints with negative coefficient for variable on right-hand-side.
2559- Fixed bug with multi-aggregated integer variables in cons_xor.
2560- Fixed bug with changed number of variables in storing relaxation solution in probing/diving.
2561- Fixed issues with scip statistics
2562- Fixed issue with multi-aggregated variables
2563- Fixed issue in with buffer memory in cons_cumulative
2564
2565@section RN701 SCIP 7.0.1
2566*************************
2567
2568Build system
2569------------
2570
2571### Cmake
2572
2573- Fixed cmake module for Ipopt to support Ipopt 3.13
2574- Added cmake variable BLISS_LIBRARY_DIR to pass a bliss library
2575- Added warning to require minimal GCC version 4.8
2576- Renamed FindCriterion cmake findmodule to FindCRITERION
2577
2578### Makefile
2579
2580- Updated make/make.project for macOS
2581- Add SANITZERFLAGS (only OPT=dbg) to LDFLAGS also if SHARED=true (and rename SANITZERFLAGS to SANITIZERFLAGS)
2582- Fixed GCC version check in make/make.linux.gnu.dbg
2583
2584Fixed bugs
2585----------
2586
2587- Fixed handling of constant term in quadratic objective of pip-reader
2588- Fixed incorrect value string for parameter estimation/completiontype
2589- Fixed initialization of first LP which led to wrong output about LPs not resolved correctly
2590- Fixed bug in SCIPcutpoolClear() function not clearing internal datastructures properly
2591- Fixed inability to set a value in a solution if it was within epsilon to the current value
2592- Fixed problems for linking optimized code with debug library of SCIP (and vice versa) by moving debug-only members
2593 to end of SCIP structs
2594
2595Miscellaneous
2596-------------
2597
2598- Variables that are marked as relaxation-only are no longer checked against debug solutions if
2599 they are captured by the transformed problem only.
2600
2601@section RN700 SCIP 7.0.0
2602*************************
2603
2604Features
2605--------
2606
2607- Using the parameter "propagating/symmetry/recomputerestart" one can now decide to recompute symmetries after a
2608 restart or not. Previously one could just turn off symmetry computation after a restart. If orbital fixing
2609 has found a reduction before the restart occured, symmetries have to be updated to ensure correctness.
2610 To this end, the user can decide via "propagating/symmetry/disableofrestart" whether orbital fixing is disabled or
2611 whether symmetries are recomputed.
2612
2613- extended relaxators statistics in solve statistics about information on number of cutoffs, improved bounds, etc.
2614
2615- extends SMPS file reader for the stochastic information, the sto files, to read a lower bound for the discrete
2616 scenarios. The lower bound is used when creating the auxiliary variables for Benders' decomposition.
2617
2618- extended Benders framework to solve NLPs and generate optimality and feasibility cuts from their solution
2619 when the subproblem is convex nonlinear.
2620
2621- extended Benders framework to create copies of Benders decompositions that can be used in a multithreading environment
2622
2623- additional functionality has been added to enable the transfer of Benders' decomposition cuts between different SCIP
2624 instances, e.g., when used in UG
2625
2626- LP rows (SCIP_ROW) can now store pointer to a constraint from which the row originates
2627
2628- Trust region, a new LNS heuristic, has been added to SCIP as both a standalone primal heuristic heur_trustregion.c
2629 and as a neighborhood inside of Adaptive Large Neighborhood Search (heur_alns.c). This heuristic is designed to improve the
2630 heuristic performance of the Benders' decomposition algorithm. It builds upon the successful trust region approaches
2631 applied to Benders' decomposition.
2632
2633- Modularity of symmetry handling has been increased. It is now possible to use orbitopes (i.e., polyhedral symmetry
2634 handling techniques) and orbital fixing on the same instance.
2635
2636- cut strengthening enabled within the Benders' decomposition framework. This uses a mix of the Improved Magnanti-Wong
2637 method and Kelly's method. The cut strengthening is enabled by setting the paramemter
2638 "benders/<bendersname>/cutstrengthenenabled" to TRUE. The parameters "cutstrengthenmult", "noimprovelimit" and
2639 "corepointperturb" control the behavior of the cut strengthening method. Additionally, the parameter
2640 "cutstrengthenintpoint" allows the user to specify the solution that is used to initialize the core point. The options
2641 are the first LP solution, the first integer feasible solution, a relative interior point, a solution vector of all
2642 ones and a solution vector of all zeros. Also, the core point can be reinitialized after each update to the incumbent
2643 solution.
2644
2645- added option to adjust weights of different scores in relpscost (hybrid) branching rule based on degeneracy information
2646 and skip strong branching for very high degeneracy rates
2647
2648- added new SCIP_DECOMP* object to store user decompositions. The user can specify one or several decompositions by assigning variable
2649 and/or constraint labels either through the API or by reading a file in DEC format (which is one of the formats that GCG writes).
2650 This format specifies constraint labels, variable labels are inferred from that. The decomposition is transformed after presolving.
2651- statistics regarding the number of blocks, the largest and smallest blocks, the border, and the constraint graph are printed for the original decomposition,
2652 and for each decomposition after presolving.
2653- the decomposition can be used as initial decomposition for the Benders functionality of SCIP.
2654- new subsection "How to provide a problem decomposition" in the SCIP documentation
2655
2656- GINS heuristic can make use of a user-provided decomposition labels in two ways:
2657 1. by selecting a block of variables that maximizes the potential, and randomly selecting a start variable for the neighborhood and/or
2658 2. by selecting an interval of consecutive blocks as neighborhood, until fixing rate is reached. In this case, no variable is randomly selected.
2659
2660- extend potential parameter of GINS to allow computation based on local LP solution, as well
2661
2662- new primal heuristic Adaptive Diving, which registers all publicly available dive sets from other diving heuristics.
2663 At each call, it selects one of the available dive sets based on the user's score type choice (heuristics/adaptivediving/scoretype).
2664 During the solution process, the heuristics learns online which divesets reach the best score, and executes them more frequently.
2665 The statistic output for Diving heuristics has been extended to incorporate the statistics of each dive set within Adaptive diving.
2666
2667- Added new penalty alternating direction method (PADM) primal heuristic that splits the problem into several sub-SCIPs
2668 according to a user-provided decomposition. The sub-SCIPs are solved on an alternating basis until a feasible solution of
2669 the original problem is found.
2670
2671- Symmetry handling constraints (cons_orbisack, cons_orbitope, cons_symresack) now have an additional parameter to encode
2672 whether they are model constraints, i.e., define the problem, or whether they are only present to handle symmetries.
2673
2674- The symmetry code has been completely restructured. The presolvers presol_symbreak and presol_symmetry as well as the propagator
2675 prop_orbitalfixing have been merged into the single propagator prop_symmetry to avoid storing the same information
2676 multiple times. This propagator is now responsible for adding symmetry handling constraints as well as activating orbital
2677 fixing. Moreover, the new file symmetry.c contains general functions for symmetry computations like orbit computations.
2678
2679- Variables can now be marked as "relaxation-only". This flag should be used to introduce new variables that are required
2680 to define a relaxation, but that are not part of any checked constraints. Essentially, these variables should only be used
2681 in the current SCIP solve and disregarded after a restart or in SCIP copies. Hence, these variables are not copied by SCIPcopy and
2682 SCIPgetVarCopy, they are currently not used in conflict constraints, and cuts involving them are not upgraded to linear constraints.
2683 Relaxation-only variables cannot appear in the objective function.
2684
2685- The OSiL reader now supports nonlinear expressions of type "signpower".
2686
2687- Expressions of form abs(x)^p * x in a nonlinear constraint are now sometimes recognized and handled by abspower constraints.
2688
2689- If polyhedral symmetry handling methods are used (cons_orbisack, cons_orbitope, cons_symresack), it is now possible to
2690 recompute symmetries if a restart occured.
2691
2692- upgrade some more quadratic constraints to second-order cone constraints, that is,
2693 handle linear binary variables as if squared in simple upgrade and
2694 do not require bounds for variables that have a zero entry in the computed eigenvectors in the non-simple upgrade
2695
2696- new variable event when changing the variable type
2697
2698- It is no longer necessary to provide a SCIP pointer for the subproblem in SCIPaddBendersSubproblem if custom solving
2699 methods are defined. A NULL pointer can be supplied to SCIPaddBendersSubproblem. In this case, no internal Benders'
2700 cut generation methods can be used.
2701
2702- Using the parameter "constraints/symresack/checkmonotonicity" one can now decide to upgrade to packing/partitioning
2703 symresacks even if the underlying permutation is not monotone.
2704
2705- New branching rule `vanillafullstrong`, mostly for scientific purpose, with the following features:
2706 1) no cutoff or domain reduction: only branching;
2707 2) idempotent (optional): leave SCIP, as much as possible, in the same state before / after the strong branching calls
2708 - basically, do not update any statistic;
2709 3) donotbranch (optional): do no perform branching. So that the brancher can be called as an oracle only
2710 (on which variable would you branch ? But do not branch please);
2711 4) scoreall (optional): keep scoring variables, even if infeasibility is detected;
2712 5) collectscores (optional): store the candidate scores from the last call, which can then be retrieved by calling SCIPgetVanillafullstrongData();
2713 6) integralcands (optional): consider integral candidates for branching,
2714 i.e., get candidates from SCIPgetPseudoBranchCands() instead of SCIPgetLPBranchCands().
2715
2716- If a reference value (misc/referencevalue) is given, the primal-reference and reference-dual integrals are calculated automatically and printed within the SCIP statistics.
2717
2718- Locally valid cuts / rows are now considered for dual proof analysis when `conflict/uselocalrows` is set to TRUE.
2719
2720- Linking variables in the linking constraint handler (cons_linking.{ch}) can now be integer or continuous. The coefficients of the binary variables are therefore now stored as SCIP_Real.
2721
2722- To save memory, it is now possible to remove all variables from the internal symmetry data structures that are
2723 not affected by any symmetry.
2724
2725- Allow to filter first variables from orbits and transfer pseudo cost information to variables in orbit
2726
2727- Add integration of external MILP presolve library as a SCIP presolver plugin that runs on MILP problems
2728
2729- Parallelisation can be used when applying Benders' decomposition. There are two different forms of parallelisation
2730 available. The first is applying Benders' decomposition within a parallel branch-and-bound. This is achieved through
2731 the integration with the UG framework. The second is the use of shared memory parallelisation for solving the Benders'
2732 decomposition subproblems. A priority queue has been added to help with load balancing.
2733
2734- The Benders' decomposition framework can handle MINLPs. If a convex relaxation of the MINLP exists, then this is
2735 solved to generate optimality and feasibility cuts. The extensions to the framework are:
2736 - New generic solving methods to solve convex NLP subproblems.
2737 - Modification to benderscut_opt and benderscut_feas to enable the generation of cuts from convex NLPs.
2738 - Addition of benderscut_feasalt to generate feasibility cuts from an alternative subproblem that minimises the
2739 violation of infeasible problems.
2740 - Better handling of subproblem solution results
2741
2742- Adds a feasibility phase to the Benders' decomposition subproblem solving methods. The feasibility phase adds slack
2743 variables to each of the constraints to ensure feasibility of the subproblem. A large coefficient is given to these
2744 slack variables in the objective function to penalise constraint violations. The coefficients are progressively
2745 increased until all slack variables take the value 0.0.
2746
2747- Improved convexity check for Benders' decomposition subproblems. The constraints of the subproblem are now checked for
2748 convexity in the initialisation of the Benders' decomposition algorithm. This enables the solving of convex NLPs as
2749 Benders' decomposition subproblems.
2750
2751- Benders' decomposition can be applied using decomposition supplied in the DEC format. To apply Benders' decomposition
2752 the parameters decomposition/benderslabels and decomposition/applybenders must be set to TRUE.
2753
2754- new event handler event_estim.c/h that approximates search tree completion and estimates tree size
2755 to trigger restarts; many approximations of search tree completion and estimation, including WBE, SSG, and tree profile method
2756- new display column that reports approx. search tree completion during the search, and an overview in the statistics table
2757- added resources (script, tutorial, test data) to adapt tree size estimation to user instances.
2758
2759- Orbital Fixing uses a list of variables that have been fixed globally since the computation of symmetries to filter
2760 symmetries. Previously, some plugins were disabled, which is not necessary anymore.
2761
2762- A new presolver "dualsparsify" was added. It tries to combine columns (i.e. variables) to cancel nonzero coefficients in the constraint matrix.
2763
2764- The presolver "tworowbnd" was implemented with better performance.
2765
2766- To be able to calculate better bounds for the dual variables, the presolver "dualinfer" was extended by the ability to perform convex combinations of continuous columns.
2767
2768- allow disabling of pricers during solving process
2769
2770- added emphasis setting for numerically challenging instances
2771
2772Performance improvements
2773------------------------
2774
2775- Extended cut presolving by removing variables that been fixed at their bounds
2776
2777- Improved branching point selection when branching on externals branching candidates. Instead of using exactly the
2778 LP solution, a point closer to the middle of the variables domain is chosen.
2779
2780- Matrix presolvers that do not work on incomplete matrices now skip matrix creation if unsupported constraint types are detected.
2781
2782- consLockBenders callback implemented to add down locks on the Benders' decomposition auxiliary variables and
2783 up and down locks per subproblem for all master problem variables. This allows the use of presolving and propagation
2784 with Benders' decomposition.
2785
2786- improved performance of orbital fixing in several ways:
2787 store permutations in transposed form to improve cache efficency;
2788 reverse order to speed up filtering of permutations;
2789 handle variables globally fixed to 1 in list;
2790 use event handler to catch global fixings;
2791 speed up orbit computations;
2792 change handling of restarts;
2793 use only permutations that can contribute to a variable's orbit;
2794
2795- allow rapid learning at local nodes
2796
2797- allow to recompute cut without using fractional values for sepa_cgmip
2798
2799- restrict the number of the clique table nonzeros relative to the number of problem nonzeros, which could be a performance bottleneck.
2800
2801- variable fixings of LP face heuristic are now computed earlier; subproblem creation is skipped if not enough variables are fixed.
2802
2803- Improved domcol presolver to not require a complete representation of all constraints in the matrix
2804
2805- performance improvement of adaptive large neighborhood search heuristic on merely continuous problems. The heuristic
2806 stops if presolving in the sub-SCIP fixes less than 50 % of the current target fixing rate over all variables
2807 (including continuous).
2808
2809- reduce memory usage in symmetry detection by a staggered allocation with decreasing overhead for larger instances
2810
2811- improved full orbitope propagation using a static implementation or a dynamic reordering of orbitope rows by a global rank function
2812
2813- improved detection of packing/partitioning orbitopes
2814
2815- enable an in-tree restart if after a reasonable initialization, the estimated size of the remaining tree is large.
2816
2817
2818Examples and applications
2819-------------------------
2820
2821- added functions to set and get hmin and hmax for optcumulative constraints
2822
2823Interface changes
2824-----------------
2825
2826### New and changed callbacks
2827
2828- new optional callback `SCIP_DECL_DIVESETAVAILABLE` to check preconditions for this dive set, e.g., if an incumbent solution is available,
2829 which is passed as new argument to SCIPcreateDiveset(). SCIPcreateDiveset() has another new parameter "ispublic".
2830
2831- new callback `SCIP_DECL_CONSHDLRCOPY` and `SCIP_DECL_CONSCOPY` in cons_orbisack and cons_symresack
2832
2833- new `idempotent` argument to SCIPgetVarStrongbranchInt() and SCIPgetVarStrongbranchFrac(),
2834 so that statistics are not updated during the call. Likewise, new `updatecol` and `updatestat` arguments to SCIPcolGetStrongbranch().
2835
2836- callback `SCIP_DECL_CONSHDLRENFOLP` can now also return SCIP_SOLVELP as *result, which indicates to the SCIP core that the LP relaxation
2837 should be solved again because the primal feasibility tolerance of the LP has been tightened (using SCIPsetLPFeastol())
2838
2839- extension of SCIP_PQUEUE by a new callback SCIP_DECL_PQUEUEELEMCHGPOS to catch swaps as well as functionality to delete arbitrary elements from the priority queue.
2840
2841### Deleted and changed API functions
2842
2843- LPI:
2844 + now for all lp interfaces consistent requirements on SCIP_LPPAR:
2845 LPITLIM and BARRIERCONVTOL positive or zero; FEASTOL, DUALFEASTOL, LPTILIM strictly positive
2846 + now projecting SCIP_LPPAR values on feasible values for each lp interface
2847 + add interface to Glop
2848 + fixed mapping between scaling parameter values in Gurobi LPI lpi_grb
2849- Symmetry:
2850 + removed function SCIPseparateCoversOrbisack() in cons_orbisack.h since the orbitope constraint
2851 handler has its own implementation of this routine with advanced features now
2852 + renamed SCIPgetGeneratorsSymmetry() to SCIPgetSymmetry() and removed two arguments
2853 + extended function SCIPgetSymmetry(): It is possible to access both the original and
2854 transposed permutations matrix as well as the (independent symmetry) components of a permutation group now.
2855 + arguments of functions SCIPcreateConsOrbisack(), SCIPcreateConsBasicOrbisack(), SCIPcreateConsOrbitope(),
2856 SCIPcreateConsBasicOrbitope(), SCIPcreateConsSymresack(), SCIPcreateConsBasicSymresack(), and SCIPcreateSymbreakCons() extended
2857 by "ismodelcons" to encode whether the constraints are model constraints or not
2858 + the function SCIPgetSymmetry() no longer accepts the parameter recompute, but has parameter permvarmap as new input
2862 + add function SCIPcomputeOrbitsComponentsSym() to compute orbits without filtering permutations and indices of orbits for each variable
2863- SCIPallowObjProp() and SCIPallowDualReds() are deprecated and replaced by SCIPallowWeakDualReds() and SCIPallowStrongDualReds(), respectively
2864- Benders' decomposition
2865 + changed SCIPstoreBenderscutCut() in scip_benders.c to SCIPstoreBendersCut(). Where this function used to take a
2866 SCIP_BENDERSCUT pointer, it now accepts a SCIP_BENDERS pointer.
2867 + the functions SCIPsolveBendersSubproblem() no longer accepts the parameter type. The type is not a necessary
2868 argument for the subproblem solving method.
2869 + arguments of functions SCIPbendersSolveSubproblemLP(), SCIPbendersSolveSubproblemCIP(), and SCIPbendersOnlyCheckConvexRelax() changed
2870 - removed SCIPbenderscutGetNAddedCuts() and SCIPbenderscutGetAddedCutData()
2871
2872
2873### New API functions
2874
2875- new argument "onlyifcomplete" in SCIPmatrixCreate() to skip matrix creation right after detecting unsupported constraint types
2876 and new arguments to count statistics when doing a clean-up of inactive variables in the constraints before building the matrix
2877
2878- new argument "threadsafe" in SCIPcopy(), SCIPcopyConsCompression(), SCIPcopyOrig(), SCIPcopyOrigConsCompression and
2879 SCIPcopyBenders(). This argument must only be set to TRUE if the source and target SCIP instances are to be solved in
2880 parallel. Setting this argument to TRUE has a performance cost.
2881
2882- new argument "append" in SCIPsetModifiedDefaultSettingsIpopt()
2883- functions SCIPclearRelaxSolVals(), SCIPsetRelaxSolVal(), SCIPsetRelaxSolVals(), SCIPsetRelaxSolValsSol(), and SCIPmarkRelaxSolValid()
2884 receive an additional argument "relax" to store the relaxation handler as creator of the relaxation solution.
2885
2886- LP:
2887 - SCIProwGetOriginCons() now returns a SCIP_CONS* instead of a SCIP_CONSHDLR*, use SCIProwGetOriginConshdlr() for the previous behavior
2888 - SCIPcreateRowCons() and SCIPcreateEmptyRowCons() now expect a SCIP_CONS* instead of a SCIP_CONSHDLR*,
2889 use SCIPcreateRowConshdlr() and SCIPcreateEmptyRowConshdlr(), respectively, for the previous behavior
2890 - deprecated SCIPlpfeastol() and SCIPchgLpfeastol(), use SCIPgetLPFeastol() and SCIPsetLPFeastol()
2891
2892- new parameter "divecontext" for every function that queries statistics for a diveset. The context can be used to distinguish between the dive set
2893 as single (standalone) heuristic or within Adaptive Diving.
2894- new parameters "divecontext" and "iterlim" to SCIPperformGenericDivingAlgorithm() to control in which context (single,adaptive) statistics are updated.
2895
2896- SCIPcopyVars, SCIPcopy, SCIPcopyConsCompression, and SCIPgetVarCopy do not copy variables that are marked as relaxation-only,
2897 thus it cannot be assumed anymore that each active variable from the master SCIP also has a counterpart in the copy.
2898 SCIPcopy, SCIPcopyConsCompression, and SCIPcopyConss can now return *valid=TRUE if some non-checked and non-enforced constraints were not copied, e.g.,
2899 because they involved relaxation-only variables. Thus, a copy is already regarded as valid if all checked or enforced constraints were copied successfully.
2900
2901- linking constraint handler:
2902 - changed type of vals argument from int* to SCIP_Real* in SCIPcreateConsLinking() and SCIPcreateConsBasicLinking()
2903 - SCIPgetIntvarLinking() has been renamed to SCIPgetLinkvarLinking().
2904 - changed return value of SCIPgetValsLinking() from int* to SCIP_Real*.
2905 - new function SCIPgetBinvarsDataLinking().
2906
2907- SCIPbendersCheckSubproblemOptimality() now returns a boolean indicating whether the subproblem is optimal or not.
2908 Previously this result was returned through a parameter. The change was required to facilitate the integration with
2909 the UG framework.
2910
2911- deleted SCIPcombineTwoInt(), SCIPcombineThreeInt(), SCIPcombineFourInt(); use the appropriate SCIPhashTwo(), ..., SCIPhashSeven() function instead
2912
2913- SCIPsetupBendersSubproblem takes a parameter of the enforcement type.
2914
2915- SCIPcreateNlpiProb takes a hashmap to store the map between the nlrows and the index in the nlrow array.
2916
2917### New API functions
2918
2919- SCIPallowWeakDualReds() and SCIPallowStrongDualReds() replace the deprecated SCIPallowObjProp() and SCIPallowDualReds(), respectively
2920- functions have been added to facilitate the transfer of Benders' decomposition cuts between solvers in UG. These include
2921 SCIPapplyBendersStoredCuts(), SCIPbendersGetNStoredCuts(), SCIPbendersGetStoredCutData() and
2922 SCIPbendersGetStoredCutOrigData().
2923- added SCIPisConvexAbspower()
2924- new functions SCIPsolGetType(), SCIPsolGetRelax(), SCIPsolSetRelax(), SCIPsolSetLPRelaxation(), SCIPsolSetStrongbranch(),
2925 SCIPsolSetPseudo to set or query the new type attribute of a primal solution. The type attribute gives information
2926 about the origin of the solution, ie, whether it was created by a relaxation handler,
2927 by the LP relaxation, by strong branching, by the current pseudo solution, or by a primal heuristic.
2928 The meaning of the argument 'heur' in all creation methods for primal solutions such as SCIPcreateSol() stays unchanged.
2930- new API functions SCIPsetCommonSubscipParams(), SCIPtranslateSubSol(), and SCIPtranslateSubSols() shared by several Large Neighborhood Search heuristics.
2931- new API function SCIPgetLPDualDegeneracy() to get two measures for the dual degeneracy of the current LP
2932- new API functions SCIPdivesetIsAvailable() to check preconditions of a dive set and SCIPdivesetIsPublic() to check if the dive set can be used
2933 by other primal heuristics.
2934- new API functions SCIPcomputeOrbitsSym(), SCIPcomputeOrbitsFilterSym(), SCIPgetPropertiesPerm(), SCIPdetermineBinvarAffectedSym(),
2935 SCIPdetermineNVarsAffectedSym(), SCIPcomputeComponentsSym(), and SCIPextendSubOrbitope(), SCIPgenerateOrbitopeVarsMatrix() for symmetry computations
2936- new API functions SCIPvarIsRelaxationOnly() and SCIPvarMarkRelaxationOnly() to query and set, resp., whether a variable is marked as relaxation-only
2937- new API functions SCIPconshdlrGetNUpdateConss() and SCIPconshdlrGetUpdateConss(), for expert users only
2938- new API function SCIPgetNConflictDualproofsApplied()
2939- new API functions SCIPeventGetOldtype() and SCIPeventGetNewtype() for the new event when changing the variable type
2940- new API function SCIPisConvexConsQuadratic() to check whether a quadratic constraint is convex when a given set of variables would be fixed
2941- new API functions SCIPgetLPFeastol(), SCIPsetLPFeastol(), and SCIPresetLPFeastol() to get, set, and reset (to the default), respectively, the primal
2942 feasibility tolerance for the LP relaxation
2943- new API functions SCIPcleanupConss{Linear,Varbound,Setppc,Logicor,Knapsack}() to clean up inactive variables from those types of linear constraints
2944- new API function SCIPsetBendersSubproblemComp() used to add a custom comparison method for ordering the Benders'
2945 decomposition subproblem solves. The comparison method is used to help with load balancing.
2946- new API function SCIPgetRowObjParallelism to get the objective parallelism of a row
2947- new API function SCIPcolGetAge to get the age of a column
2948- added SCIPhashThree(), SCIPhashFive(), SCIPhashSix(), and SCIPhashSeven() that complement SCIPhashTwo(), SCIPhashFour() to combine 32bit integers to
2949 a 32bit hash value
2950- new API function SCIPgenerateAndApplyBendersOptCut is used to generate a Benders' optimality cut using the dual
2951 solutions. This function can be supplied vectors for the primal and dual solution for generating an optimality cut.
2952 This avoids the need for a SCIP instance to solve the Benders' decomposition subproblem and generating cuts.
2953- new API function SCIPconsAddCoef used for adding a coefficient to a linear-type constraint.
2954- new API functions SCIPconsNonlinearGetRhs, SCIPconsNonlinearGetLhs and SCIPconsNonlinearAddLinearCoef for getting the
2955 RHS and LHS from a nonlinear-type constraint and adding a linear coefficient to the constraint.
2956- new API function SCIPbendersSolSlackVarsActive for checking whether any slack variables from the feasibility phase are
2957 active in the subproblem solution.
2958- new API functions SCIPbendersSetSubproblemType and SCIPbendersGetSubproblemType sets and gets the subproblem type.
2959 This is either:
2960 - Convex constraints with continuous variables
2961 - Convex constraints with discrete variables
2962 - Non-convex constraints with continuous variables
2963 - Non-convex constraints with discrete variables
2964- new API functions SCIPbendersSetSubproblemIsNonlinear() and SCIPbendersSubproblemIsNonlinear() for setting and
2965 identifying whether the Benders' decomposition subproblems contain nonlinear constraints. Similarly, the functions
2966 SCIPbendersSetMasterIsNonlinear() and SCIPbendersMasterIsNonlinear() sets and identifies whether the Benders'
2967 decomposition master problem contains nonlinear constraints.
2968- new API function SCIPapplyBendersDecomposition for applying Benders' decomposition given a decomposition in the DEC
2969 format
2970- new API function SCIPwasNodeLastBranchParent to query if a node has been the parent of the most recent branching in the tree
2971- new API functions SCIPtreemodelInit(), SCIPtreemodelFree(), SCIPtreemodelIsEnabled(), SCIPtreemodelSelectCandidate() related to the new
2972 treemodel way of comparing branching candidates. These functions are only currently used for reliability pscost branching, but they can be used
2973 in other parts of the code.
2974- New function SCIPcalcChildEstimateIncrease() to compute the increase in the child estimation
2975- new API functions SCIPisOrbitalfixingEnabled() and SCIPgetSymmetryNGenerators() to check whether orbital fixing is
2976 enabled and to get the number of generators of the current symmetry group, respectively
2977- new API function SCIPdelNlRow() to remove a row from the NLP
2978
2979### Event system
2980
2981- new event type SCIP_EVENTTYPE_NODEDELETE to react on nodes that are about to be deleted from the tree
2982
2983### Changed parameters
2984
2985- renamed parameter "propagating/orbitalfixing/enableafterrestart" to ".../symmetry/recomputerestart"
2986- Parameter "misc/allowdualreds" is now called "misc/allowstrongdualreds"
2987- Parameter "misc/allowobjprop" is now called "misc/allowweakdualreds"
2988- changed default values of propagation (new value: 1, old value: 5) and separation frequency (new value: -1, old value: 5) in cons_orbitope.c
2989- all primal heuristics that use sub-SCIPs are disabled within the heuristics fast emphasis setting
2990- deleted parameter heuristics/localbranching/useuct, use heuristics/useuctsubscip instead
2991- changed default value of "presolving/symbreak/detectorbitopes" (new value: TRUE, old value: FALSE)
2992- extended range of "misc/usesymmetry" (new range: [0,3], old range: [0,2])
3007- changed default value of "heuristics/coefdiving/freq" (old: 10, new: -1)
3008- changed default value of "heuristics/conflictdiving/freq" (old: -1, new: 10)
3009- changed default value of "heuristics/conflictdiving/lockweight" (old: 1.0, new: 0.75)
3010- replaced parameter "numerics/lpfeastol" by "numerics/lpfeastolfactor" to specify which factor should be applied to the SCIP feasibility
3011 tolerance to initialize the primal feasibility tolerance of the LP solver
3012- enabling aggressive presolving now activates all available presolving plugins,
3013 and decreases the presolving/restartfac parameter correctly with respect to default.
3014- changed default value of heuristics/rins/nodesquot to 0.3 (was 0.1), to compensate
3015 the removal of a hard coded factor of 3.0 in the code without affecting the default behavior
3016 of the RINS heuristic.
3017- changed default value of "constraints/quadratic/empathy4and" (old: 0, new: 2)
3018- changed default value of "propagating/redcost/useimplics" (old: TRUE, new: FALSE)
3019
3020### New parameters
3021
3022- the possibility to define the Benders' decomposition auxiliary variables as implicit integer is provided. This
3023 behavior is controlled with an additional parameter in the Benders' decomposition framework.
3024- added parameter benders/<bendersname>/cutcheck to enable the generation of Benders' decomposition cuts during solution
3025 checking.
3026- constraints/orbitope/usedynamicprop: the possibility to propagate orbitope constraints by reordering the rows based on the
3027 branching strategy is provided (only possible for non-model constraints)
3028
3029- new parameters heuristics/shiftandpropagate/minfixingratelp and heuristics/locks/minfixingratelp to stop the
3030 heuristics after propagating integer fixings if no sufficient fixing of the all variables (including continuous)
3031 could be achieved. These parameters help to avoid solving LP's that are comparable in hardness to the main root LP.
3032
3033- Added parameters branching/midpull and branching/midpullreldomtrig to control by how much to move
3034 the branching point for an external branching candidate closer to the middle of the candidates domain. The
3035 default of 0.75 and 0.5, respectively, uses a point that is 75*alpha% closer to the middle of the domain, where
3036 alpha is the relative width of the candidates domain (width of local domain divided by width of global domain),
3037 if the latter is below 0.5, and alpha=1.0 otherwise. That is, with the default settings, a branching point is
3038 chosen closer to the middle of the candidates domain if the variables local domain is still similar to its
3039 global domain, but is chosen closer to the LP solution if the local domain is much smaller than the global
3040 domain.
3041
3042- Added parameter lp/minmarkowitz to set the Markowitz stability threshold (range 0.0001 to 0.9999).
3043 High values sacrifice performance for stability.
3044
3045- Added parameters benders/<bendersname>/lnsmaxcalls and benders/<bendersname>/lnsmaxcallsroot to the Benders'
3046 decomposition core. These parameters limit the number of Benders' decomposition subproblem checks, for the full
3047 branch-and-bound tree and root node respective, when solving the auxiliary problem of LNS hueristics. These
3048 parameters only have effect if the lnscheck parameter is set to TRUE.
3049
3050- Added parameter cons/linear/maxmultaggrquot to limit the maximum coefficient dynamism of an equation on which
3051 multiaggregation is performed. This replaces a compiler define of the same name.
3052 Default value is 1000, smaller values make multiaggregations numerically more stable.
3053- new global parameter heuristics/useuctsubscip that affects all LNS heuristics using common sub-SCIP parameters
3054
3055- new parameter branching/relpscost/degeneracyaware to switch degeneracy-aware hybrid branching
3056
3057- new parameter separation/rapidlearning/checkexec to check whether rapid learning is allowed to run locally
3058- new parameters separation/rapidlearning/check{degeneracy,dualbound,leaves,nsols,obj} to enable checking the respective feature for local rapid learning
3059- new parameter separation/rapidlearning/maxcalls to limit the number of rapid learning executions
3060- new parameter separation/rapidlearning/nwaitingnodes to set the number of waiting nodes before the dual bound is checked
3061- new parameter separation/rapidlearning/mindegeneracy to set the minimal threshold of degenerate basic-variables
3062- new parameters separation/rapidlearning/minvarconsratio to set the minimal ratio of unfixed variables in relation to basis size
3063
3064- new parameters to control the Benders' decomposition two-phase method.
3065 - constraints/benderslp/depthfreq: after the maxdepth is reached, then the two-phase method will only be called at
3066 nodes at a depth divisible by depthfreq.
3067 - constraints/benderslp/stalllimit: after the maxdepth is reached, if there has been no improvement in the dual bound
3068 for stalllimit number of nodes, then the two-phase method is executed for the next fractional LP solution that is
3069 encountered.
3070 - constraints/benderslp/iterlimit: after the root node, only iterlimit fractional LP solutions are used at each node
3071 to generate Benders' decomposition cuts.
3072
3073- new parameters for symmetry handling
3074 - new parameter "propagating/symmetry/maxgenerators"
3075 - new parameter "propagating/symmetry/checksymmetries"
3076 - new parameter "propagating/symmetry/displaynorbitvars"
3077 - new parameter "propagating/symmetry/conssaddlp"
3078 - new parameter "propagating/symmetry/addsymresacks"
3079 - new parameter "propagating/symmetry/detectorbitopes"
3080 - new parameter "propagating/symmetry/addconsstiming"
3081 - new parameter "propagating/symmetry/ofsymcomptiming"
3082 - new parameter "propagating/symmetry/performpresolving"
3083 - new parameter "propagating/symmetry/recomputerestart"
3084 - new parameter "constraints/symresack/checkmonotonicity"
3085 - new parameter "propagating/symmetry/compresssymmetries"
3086 - new parameter "propagating/symmetry/compressthreshold"
3087 - new parameter "propagating/symmetry/disableofrestart"
3088 - new parameter "propagating/symmetry/symfixnonbinaryvars"
3089
3090- new parameter for enabling shared memory parallelisation for solving Benders' decomposition subproblems. The parameter
3091 benders/<bendersname>/numthreads sets the number of threads used for parallel subproblem solving.
3092
3093- new parameters to control enhancements for solving MINLPs by Benders' decomposition
3094 - benders/<bendersname>/execfeasphase: enables the feasibility phase for solving the Benders' decomposition
3095 subproblems
3096 - benders/<bendersname>/slackvarcoef: the initial coefficient of the slack variable for the feasibility phase
3097 - benders/<bendersname>/checkconsconvexity: should the constraints be checked for convexity. This can be set to FALSE
3098 if you are certain that the NLP subproblem is convex.
3099
3100- new parameter presolving/clqtablefac (default value 2.0) as limit on number of entries in clique table relative to number of problem nonzeros
3101
3102- new parameter conflict/uselocalrows (default: TRUE) to incorporate locally valid cuts / rows for dual proof analysis
3103
3104- new return code SCIP_NOTIMPLEMENTED for functions, e.g., in the LPI that have not been implemented (yet)
3105
3106- new parameter separating/cgmip/genprimalsols that allows to generate initial primal solutions from Gomory cuts
3107
3108- new parameter branching/relpscost/filtercandssym to allow filtering from orbits
3109
3110- new parameter branching/relpscost/transsympscost to transfer pseudo cost information to orbit
3111
3112- new parameters for tree size estimation and restarts:
3113 - estimation/restarts/restartpolicy (default value n)
3114 - estimation/method (default value c)
3115 - estimation/restarts/restartlimit (default value 1)
3116 - estimation/restarts/minnodes (default value 1000)
3117 - estimation/restarts/countonlyleaves (default value FALSE)
3118 - estimation/restarts/restartfactor (default value 2)
3119 - estimation/coefmonoprog (default value 0.3667)
3120 - estimation/coefmonossg (default value 0.6333)
3121 - estimation/restarts/hitcounterlim (default value 50)
3122 - estimation/reportfreq (default value -1)
3123 - estimation/regforestfilename (default value "-")
3124 - estimation/completiontype (default value a)
3125 - estimation/treeprofile/enabled (default value FALSE)
3126 - estimation/treeprofile/minnodesperdepth (default value 20)
3127 - estimation/useleafts (default value TRUE)
3128 - estimation/ssg/nmaxsubtrees (default value -1)
3129 - estimation/ssg/nminnodeslastsplit (default value 0)
3130
3131- new parameter constraints/linear/extractcliques to turn clique extraction off
3132
3133- new emphasis setting emphasis/numerics to increase numerical stability of (mostly) presolving operations such as (multi-)aggregations at the cost of performance.
3134
3135- new parameters for treemodel:
3136 - new parameter branching/treemodel/enable to enable the treemodel in reliability pscost branching and possible
3137 future parts of the code where it could be used.
3138 - new parameter branching/treemodel/highrule to specify which branching rule to use when treemodel thinks the node
3139 is high in the tree.
3140 - new parameter branching/treemodel/lowrule to specify which branching rule to use when treemodel thinks the node
3141 is low in the tree.
3142 - new parameter branching/treemodel/height to specify at which (estimated) height a node is high or low in the tree.
3143 - new parameter branching/treemodel/filterhigh to specify whether to filter dominated candidates in nodes which are
3144 high in the tree.
3145 - new parameter branching/treemodel/filterlow to specify whether to filter dominated candidates in nodes which are
3146 low in the tree.
3147 - new parameter branching/treemodel/maxfpiter to specify the maximum number of fixed-point iterations to use when
3148 computing the ratio of a variable using the fixed-point method.
3149 - new parameter branching/treemodel/maxsvtsheight to specify the maximum height to compute the SVTS score exactly
3150 before approximating it using the ratio.
3151 - new parameter branching/treemodel/fallbackinf defines the fallback strategy to use when the tree size estimates
3152 obtained by SVTS are infinite.
3153 - new parameter branching/treemodel/fallbacknoprim defines the fallback strategy to use when no primal bound is known
3154 and thus SVTS would not be able to compute a tree size (it would be infinite).
3155 - new parameter branching/treemodel/smallpscost defines the value under which pscosts are considered too small to be
3156 the deciding factor for branching, in which case it may be better not to use the treemodel.
3157
3158- new parameters for symmetry handling constraint handlers to enforce that also non-model constraint are copied:
3159 - new parameter "constraints/orbisack/forceconscopy"
3160 - new parameter "constraints/orbitope/forceconscopy"
3161 - new parameter "constraints/symresack/forceconscopy"
3162
3163
3164### Data structures
3165
3166- small changes in constants of hash functions
3167- added fast 2-universal hash functions for two to seven 32bit elements with 32bit output
3168- extended SCIPpqueueCreate() by additional callback argument SCIP_DECL_PQUEUEELEMCHGPOS to catch position changes
3169- new methods SCIPpqueueDelPos() to delete elements at a specific position in the priority queue and SCIPpqueueFind() to
3170 find a specific position. It is recommended to track position changes using the new callback SCIP_DECL_PQUEUEELEMCHGPOS.
3171 In contrast, using SCIPpqueueFind() can be slow because it needs to compare the element it searches for
3172 with each slot in the queue.
3173
3174### Build system
3175
3176- The default value for DFLAGS in the non-cmake buildsystem has changed from -MM to -MMD. This will break the
3177 generation of depend.* files if that was done by a compiler call that relied on -MM. The new preferred way
3178 to handle compilation dependencies is to additionally use $(DFLAGS) when compiling the object files (.o) and
3179 to include the generated .d files in the Makefile, see also "Build system / Makefile" below.
3180
3181Unit tests
3182----------
3183 - new unit test for treemodel.
3184
3185Testing
3186-------
3187
3188 - fixed an issue that may have lead to wrong status reports in the evaluation scripts
3189
3190Build system
3191------------
3192
3193### Cmake
3194
3195- avoid problem with doubly defined object together with CPLEX
3196
3197### Makefile
3198
3199- Removed static object compilation dependency files (depend.*). If using a GCC compatible compiler, then dependency
3200 files are now dynamically created and updated during build. The new dependency files (*.d) reside next to each object
3201 file (.o) in the corresponding obj subdirectory.
3202- added support for building against Ipopt >= 3.13
3203- unify compiler switches for Intel compiler and avoid problem with doubly defined object together with CPLEX
3204
3205Fixed bugs
3206----------
3207
3208- fix and improve memory handling in symmetry computation
3209- fix shown number of applied conflicts in solving statistics
3210- fix wrongly skipping strong branching call and using old information if LP was solved with 0 iterations
3211- fix minor bug in cut score calculation
3212- fixed several bugs related to rounding locks of variables not being updated correctly
3213- small fix in cons_varbound.c to skip changing bounds of multi-aggregated variables in separation callback
3214- fixed issue in SCIPtightenVar* and SCIPinferVar* that occurs for small bound changes
3215- fixed rejecting minimal boundchange that changed sign of variable, even though SCIPisLb/UbBetter approved it
3216- fixed issue in generateCutNonConvex() which is triggered when adding quadratic constraints during the solving process
3217- fixed bug in freeing the reoptimization data if no problem exists
3218- fixed bug in SCIPreoptReleaseData() when freeing all stored constraints
3219- fixed bug when freeing the transformed problem via interactive shell if reoptimization is enabled
3220- fixed two issues related to (near-)redundant logicor constraints in presolving
3221- fixed counting of aggregations in XOR constraint handler
3222- fixed handling of unbounded solutions
3223- fixed update of LP size information when an LP error occured during probing
3224- handle special case of variable bound constraints during aggregating variables
3225- tighten sides of linear constraints before trying to upgrade them to more specialized constraints (knapsack, logic-or etc.) when calling SCIPupgradeConsLinear()
3226- fixed an issue in repair heuristic in the case of loose (noncolumn) variables
3227- allow user to correctly set heuristics/alns/(un)fixtol
3228- fixed an issue in heur_completesol which is triggered during bound widening of unbounded continuous variables
3229- fixed bug in cons_indicator if addopposite is true
3230- fixed bug in sepa_disjunctive: treat case that conflictgraph is empty
3231- added safety check in conversion to rational number to avoid overflow
3232- fixed bug in interval evaluation with power-operator in certain situations
3233- fixed behavior of SCIPmatrixCreate() regarding memory management and column generation
3234- SCIPmatrixCreate() returns complete=FALSE when locks do not add up
3235- fixed bug in sepa_oddcylce when variables are fixed
3236- fixed numerical issues related to tighter constraint sides in varbound constraint handler
3237- fixed update of watchedvars in logicor constraint handler in case of a restart during the tree
3238- fixed treatment of multi-aggregated variables in logicor constraint handler
3239- handle special case of redundant implications
3240- fixed numerical issue related to almost-0-values in pseudosolution conflict analysis
3241- fixed numerical issue related to very large greatest common dividers in linear constraint handler
3242- avoid using implications on multiaggregated variables when propagating implications
3243- fixed creation of (Lagrangian) variable bounds in the OBBT propagator
3244- fixed sorting of primal solutions
3245- fixed cleaning of clean buffer in conflict analysis
3246- avoid probing on variables with huge bounds in shift and propagate heuristic
3247- fix issue in printing solutions for variables that have been added by the dual sparsify presolver
3248- fix issue related to fixing redundant logic-or constraints after presolving
3249- fixed bug when parsing logic-or and and-constraints
3250- fixed wrong assert in updateLazyBounds()
3251- fixed bug in pricestore, which resulted in too many problem variables being added
3252- fixed bug in cons_knapsack where weight of clique was not reset after an infeasibility was detected
3253- fixed bug in presol_inttobinary which did not take into account that the aggregation could be rejected due to numerics
3254- fixed bug in debug solution mechanism in connection to variables created by presol_inttobinary
3255- fixed wrong indexing while undoing the implications from a redundant variable in SCIPshrinkDisjunctiveVarSet
3256- redundancy checks in SCIPnodeAddBoundinfer now take a possible change to an active variable into account
3257- fixed adding already added quadratic rows to NLP relaxation during solve
3258- fixed issue related to variable locks in the varbound constraint handler
3259- fixed bug in the quadratic constraint handler when changing infinite constraint sides
3260- fixed sorting of variables in linear constraint handler
3261- added additional checks to ensure numerical stability of dual proofs
3262- fixed a case when activities of a linear constraint got unreliable but where still used for reductions
3263- ensure that lhs <= rhs for linear constraints (without tolerances)
3264- make handling of read errors in SCIPfread() consistent between version with and without ZLIB
3265- correctly drop variable events in cons_indicator in restart
3266- fixed bug in cons_orbitope with upgrading of orbitope constraints
3267- additional checks in some presolvers for time limit being exceeded
3268- fixed bug in presolving of cons_varbound with multi-aggregated variables
3269- improve numerics in conflict analysis by using double-double arithmetic
3270- fixed bound acceptance condition to avoid inconsistencies
3271- fixed numerics in pseudoobj propagator by using double-double arithmetic
3272
3273Miscellaneous
3274-------------
3275
3276- modified display column for memory usage ("mem"), which reports the memory usage most of the time, but shows the creator name
3277 (heuristic, relaxation handler, LP relaxation, strong branching, pseudo solution) of every new incumbent solution. Together with this change,
3278 heuristic display characters have been unified to represent the type of the heuristic
3279 (diving, Large neighborhood search, propagation, etc.), see also type_heur.h.
3280- added assert that ensures that the locks of a variable have been decreased to 0 when it is freed
3281- added more output for completing a partial solution
3282- checks in debug mode that clean buffer memory is really clean when being freed are now disabled by default
3283- don't compute symmetries if reoptimization is enabled
3284- prefer integral values when fixing an almost-fixed continuous variable in the trivial presolver
3285- changed the name of the variable that is added by the OSiL reader to represent the quadratic or nonlinear parts of the objective function
3286- SCIP_EXPORT is now defined as __attribute__((__visibility__("default"))) if GCC and no SCIP config header is used
3287
3288@page RN6 Release notes for SCIP 6
3289
3290@section RN602 SCIP 6.0.2
3291*************************
3292
3293Features
3294--------
3295
3296- The abspower constraint handler now passes more accurate convexity
3297 information to the NLP relaxation.
3298
3299Examples and applications
3300-------------------------
3301
3302- added parsing functionality for optcumulative constraints in CIP format
3303
3304Interface changes
3305-----------------
3306
3307### Interfaces to external software
3308
3309- Updated the Mosek LP solver interface to support Mosek 9.0.
3310
3311Build system
3312------------
3313
3314### Cmake
3315
3316- new target to 'doc' to build documentation
3317- ctests now fail if parameter file not found
3318- add flag STATIC_GMP and improve GMP find module
3319- remove non-API functions from library (API functions use new macro SCIP_EXPORT)
3320- increase minimal required CMake version to 3.3
3321- correct paths and dependency information when installing SCIP
3322
3323Fixed bugs
3324----------
3325- fixed SCIP-Jack presolving bug that could lead to wrong results for Steiner arborescence problems
3326- fixed wrong unboundedness result in case not all constraints were already in the LP and enforcement was
3327 skipped because an optimal solution was found
3328- fixed wrong enforcement of constraints in the disjunction constraint handler
3329- fixed wrong behavior of concurrent solve ignoring initial solutions
3330- fixed bug in concurrent solve when problem was already solved in presolving
3331- aggregate non-artificial integer variable for XOR constraints with two binary variables and delete constraint
3332- copy the objective offset when copying the original problem
3333- fixed bug in SCIPlpiGetBInvARow in lpi_cpx using wrong size of resulting vector
3334- fixed quadratic runtime behavior in sepa_aggregation
3335- fixed statistics of separators
3336- improve numerical stability in varbound constraint handler by using double-double arithmetic
3337- fixed bug in propagation of dual proofs
3338- fixed bugs that arise for multiaggregated indicator variables by disallowing multiaggregation for them
3339- improve numerical stability in SCIPcomputeBilinEnvelope* by using double-double arithmetic
3340- fixed bug related to releasing pending bound changes in tree.c
3341- set STD FENV_ACCESS pragma to on in code that changes floating-point rounding mode
3342- disable GCC optimizations in main interval arithmetic code to prevent wrong optimizations
3343- fixed wrong assert in cons_xor concerning the variable type
3344- fixed different behavior of SCIPisLbBetter and SCIPisUbBetter between having NDEBUG defined or not
3345- correctly handle bound disjunctions in symmetry detection
3346- fixed issue in reliability branching related to the LP error flag not being reset
3347- fixed treatment of near-infinite bounds in shiftandpropagate's problem transformation
3348- fixed handling of infinite values in SCIPcomputeHyperplaneThreePoints()
3349- fixed comparisons of infinite values in heur_intshifting.c and heur_shifting.c
3350- fixed bug related to updating unprocessed cuts in the cutpool
3351- fixed bug related to enabling quadratic constraints during `CONSINITLP`
3352- add missing SCIP_EXPORT for functions used by GCG
3353- fixed memory leak and wrong initialization for trival cases in cons_symresack.c
3354- fixed bug with upgrading to packing/partitioning orbitopes
3355- fixed bug with the status while upgrading in presol_symbreak.c
3356- fixed wrong stage while clearing the conflict store
3357- fixed behavior of SCIPfixVar() by setting infeasible pointer to TRUE if fixval lies outside variable domain
3358- allow tightenVar() in SCIP_STAGE_PROBLEM stage
3359- fixed bug in cumulative constraint handler when separating the LP solution
3360- fixed issues with integer overflow in cumulative constraint handler
3361- fixed bug where the convexity of Benders' decomposition subproblems was checked even when users defined subproblem
3362 solving methods. Now, as per the documentation, the user must explicitly state whether the subproblem is convex
3363- fixed wrong indexing in heur_dualval
3364- fixed issue with basis status in SoPlex LPi
3365
3366Miscellaneous
3367-------------
3368
3369- statistics now output primal/dual bounds if objective limit is reached
3370- memory check in debug mode is now disabled by default
3371- message is now provided to the user to inform that automatic Benders' auxiliary variable lower bound computations are
3372 not activated when user defined subproblem solving methods are present
3373- corrected documentation of the primalgap in SCIP; describe when it will be infinite
3374
3375@section RN601 SCIP 6.0.1
3376*************************
3377
3378Features
3379--------
3380
3381- when using a debug solution every (multi-)aggregation will be checked w.r.t. this solution
3382
3383Performance improvements
3384------------------------
3385
3386- try greedy solution first before solving knapsack exactly using dynamic programming in SCIPsolveKnapsackExactly,
3387 compute greedy solution by weighted median selection.
3388- don't consider implied redcost by default in the reduced cost propagator
3389
3390Interface changes
3391-----------------
3392
3393### Deleted and changed API functions and macros
3394
3395- The preprocessor macro NO_CONFIG_HEADER now needs to be defined when
3396 including SCIP header files from a SCIP build or installation that
3397 has been build via the Makefile-only build system.
3398
3399- The following preprocessor macros have been renamed:
3400 WITH_ZLIB to SCIP_WITH_ZLIB, WITH_GMP to SCIP_WITH_GMP, WITH_READLINE
3401 to SCIP_WITH_READLINE, NO_SIGACTION to SCIP_NO_SIGACTION, NO_STRTOK_R
3402 to SCIP_NO_STRTOK_R, ROUNDING_FE to SCIP_ROUNDING_FE, ROUNDING_FP to
3403 SCIP_ROUNDING_FP, ROUNDING_MS to SCIP_ROUNDING_MS. Note, however, that
3404 the names of macros NO_RAND_R and NO_STRERROR_R have not been changed
3405 so far.
3406
3407### New API functions
3408
3409- SCIPhashmapInsertInt(), SCIPhashmapSetImageInt(), and SCIPhashmapGetImageInt() to use integer values as images in hashmaps
3410
3411### Command line interface
3412
3413- warn about coefficients in MPS files with absolute value larger than SCIP's value for infinity
3414
3415### Changed parameters
3416
3417- default clock type for timing is now wallclock
3418
3419Unit tests
3420----------
3421
3422- added unit tests for exact knapsack solving and (weighted) median selection algorithms
3423
3424Build system
3425------------
3426
3427### Cmake
3428
3429- add missing GMP dependency when compiling with SYM=bliss
3430- add DL library when linking to CPLEX to avoid linker errors
3431- new config.h header defining the current build configuration, e.g. SCIP_WITH_GMP
3432
3433Fixed bugs
3434----------
3435
3436- fixed handling of weights in cons_sos1 and cons_sos2 (NULL pointer to weights)
3437- fixed handling of unbounded LPs in SCIP and in several LPIs; added heuristic method to guess solution
3438- the STO reader is capable of handling scenarios defined using lower case "rhs"
3439- fixed OPB reader for instances without explicit plus signs
3440- correct dual solution values for bound constraints
3441- fixed recognition of variable with only one lock in cons_bivariate, cons_quadratic, and cons_nonlinear
3442- fixed update of constraint violations in solution repair in cons_bivariate, cons_quadratic, and cons_nonlinear
3443- print error message and terminate if matrix entries of a column are not consecutive in mps format
3444- fixed incorrect handling of fixed variables when transfer of cuts from LNS heuristic for Benders' decomposition
3445- fix returning local infeasible status by Ipopt interface if Ipopt finds problem locally infeasible
3446- skip attempt to apply fixings in linear constraint handler during solving stage as LP rows cannot change anymore
3447- fixed bug when reading >= indicator constraints in MPS format
3448- fix issue with nodes without domain changes if we ran into solution limit in prop_orbitalfixing
3449- fixed unresolved reference to CppAD's microsoft_timer() function on builds with MS/Intel compilers on Windows
3450- ignore implications added through SCIPaddVarImplication() that are redundant to global bounds also in the
3451 special case of an implication between two binary variables; also, use implications instead of cliques in the case
3452 of a binary implied variable with nonbinary active representative
3453- fixed bug with aggregated variables that are aggregated in propagation of cons_sos1
3454- fixed some special cases in SCIPselect/SCIPselectWeighted methods
3455- relaxed too strict assertion in Zirounding heuristic
3456- fixed the upgrade routine to XOR constraints: aggregate integer variable if its coefficient has the wrong sign
3457- fixed handling of nonartificial parity variables when deleting redundant XOR constraints
3458- earlier deletion of trivial XOR constraints (at most 1 operator left)
3459- fixed wrong hashmap accesses and added sanity check for the correct hashmap type
3460- avoid copying of unbounded solutions from sub-SCIPs as those cannot be checked completely
3461- corrected the output of the first LP value in case of branch-and-price
3462- fixed possible integer overflow, which led to wrong conclusion of infeasibility, in energetic reasoning of cons_cumulative.c
3463
3464Miscellaneous
3465-------------
3466
3467- do not scale linear constraints to integral coefficients
3468
3469@section RN600 SCIP 6.0.0
3470*************************
3471
3472Features
3473--------
3474
3475- new diving heuristic farkasdiving that dives into the direction of the pseudosolution and tries to construct Farkas-proofs
3476- new diving heuristic conflictdiving that considers locks from conflict constraints
3477- restructuring of timing of symmetry computation that allows to add symmetry handling components within presolving
3478- `lp/checkstability` is properly implemented for SoPlex LPI (spx2)
3479- new branching rule lookahead that evaluates potential child and grandchild nodes to determine a branching decision
3480- limits on the number of presolving rounds a presolver (maxrounds) or propagator/constraint handler (maxprerounds)
3481 participates in are now compared to the number of calls of the particular presolving method, not the number of
3482 presolving rounds in general, anymore
3483- new miscellaneous methods for constraints that have a one-row linear representation in pub_misc_linear.h
3484- a Benders' decomposition framework has been added. This framework provides the functionality for a user to solve a
3485 decomposed problem using Benders' decomposition. The framework includes classical optimality and feasibility cuts,
3486 integer optimality cuts and no-good cuts.
3487- add statistic that presents the number of resolves for instable LPs
3488- new readers for stochastic programming problems in SMPS format (reader_sto.h, reader_smps.h)
3489
3490Performance improvements
3491------------------------
3492
3493- cuts generated from certain quadratic constraints with convex feasible region are now global
3494- performance improvements for Adaptive Large Neighborhood Search heur_alns.c
3495 + all neighborhoods now start conservatively from maximum fixing rate
3496 + new default parameter settings for bandit selection parameters
3497 + no adjustment of minimum improvement by default
3498- improved bound tightening for some quadratic equations
3499- constraint handler checking order for original solutions has been modified to check those with negative check priority
3500 that don't need constraints after all other constraint handlers and constraints have been checked
3501- deactivate gauge cuts
3502
3503Examples and applications
3504-------------------------
3505
3506- new example `brachistochrone` in CallableLibrary examples collection; this example implements a discretized model to
3507 obtain the trajectory associated with the shortest time to go from point A to B for a particle under gravity only
3508- new example `circlepacking` in CallableLibrary examples collection; this example models two problems about packing
3509 circles of given radii into a rectangle
3510- new price-and-branch application for the ringpacking problem
3511- new stochastic capacitated facility location example demonstrating the use of the Benders' decomposition framework
3512
3513Interface changes
3514-----------------
3515
3516### New and changed callbacks
3517
3518- added parameter locktype to `SCIP_DECL_CONSLOCK` callback to indicate the type of variable locks
3519
3520### Deleted and changed API functions
3521
3522- Symmetry:
3523 + removed function SCIPgetTimingSymmetry() in presol_symmetry.h since this presolver does not compute symmetries independent
3524 of other components anymore
3525 + additional argument `recompute` to SCIPgetGeneratorsSymmetry() to allow recomputation of symmetries
3526
3527- Random generators:
3528 + the seed of SCIPinitializeRandomSeed() is now an unsigned int
3529 + the seed of SCIPsetInitializeRandomSeed() is now an unsigned int and it returns an unsigned int
3530 + new parameter for SCIPcreateRandom() to specify whether the global random seed shift should be used in the creation of
3531 the random number generator
3532
3533- Miscellaneous:
3534 + additional arguments `preferrecent`, `decayfactor` and `avglim` to SCIPcreateBanditEpsgreedy() to choose between
3535 weights that are simple averages or higher weights for more recent observations (the previous default).
3536 The last two parameters are used for a finer control of the exponential decay.
3537 + functions SCIPintervalSolveUnivariateQuadExpression(), SCIPintervalSolveUnivariateQuadExpressionPositive(), and
3538 SCIPintervalSolveUnivariateQuadExpressionPositiveAllScalar() now take an additional argument to specify already
3539 existing bounds on x, providing an entire interval ([-infinity,infinity]) gives previous behavior
6634 - added writing for pip files (linear, quadratic, polynomial nonlinear, polynomial abspower, polynomial bivariate, and
6635 and constraints)
6636 - CIP format variable characters defined, e.g. `SCIP_VARTYPE_INTEGER_CHAR`
6637 - Improved support for wbo format for weighted PBO problems, IBM's xml-solution
6638 format and pip and zimpl format for polynomial mixed-integer programs
6639 - New reader for (standard) bounds on variables
6640 - Extended reader for CIP models to handle various new constraints, including all types of linear constraints
6641 - flatzinc reader is now capable to read cumulative constraints
6642 - changed opb(/wbo) reader which now creates pseudoboolean constraints instead of linear- and and-constraints, only a
6643 non-linear objective will create and-constraints inside the reader and while reading a wbo file the topcost constraint
6644 is created as well
6645 - added clock for determine the time for reading
6646 - added reader for variable bounds (reader_bnd.{c,h})
6647 - Removed method SCIPreadSol(); call solution reading via SCIPreadProb() which calls the solution reader for .sol files.
6648
6649- Nonlinear:
6650 - Major extensions for nonlinear CIP, new option for n-ary branching on nonlinear variables (within pseudocost branching rule)
6651 - added BETA version of constraint handler for nonlinear constraints (cons_nonlinear.{c,h}) to handle nonlinear
6652 equations given by algebraic expressions using operands like addition, multiplication, power, exp, log, bivariate
6653 nonlinear constraints; currently no trigonometric functions
6654 - added BETA version of constraint handler for bivariate nonlinear constraints (cons_bivariate.{c,h}) to compute tight
6655 estimators for 1-convex and convex-concave bivariate nonlinear functions (given as expression tree)
6656 - the gams writer can now write nonlinear, abspower and bivariate constraints
6657 - Extended writer for GAMS and pip format to write more types of nonlinear constraints
6658 - the pip and zimpl reader now create nonlinear constraints for polynomials of degree > 2
6659
6660- Presolving:
6661 - new dual presolving methods in cons_setppc and cons_logicor
6662 - new presolving step `removeConstraintsDueToNegCliques` in locigor constraint handler which updates logicor constraints
6663 to setppc constraints if a negated clique inside this constraint exist, by default is off
6664 - new presolving step in cons_knapsack (detectRedundantVars, deleteRedundantVars) which determines redundant variables
6665 in knapsack constraint with or without using clique information
6666 - cons_logicor is now able to replace all aggregated variables in presolving by there active or negation of an active
6667 variable counterpart
6668 - prop_pseudoobj is now working in presolving as well
6669 - implement presolving in exitpre() in cons_orbitope and cons_indicator
6670
6671- Propagators:
6672 - added counter for number calls and timing for resolve propagation calls for constraint handler and propagators
6673 - Propagators are now also called in node presolving
6674 - the probing presolver presol_probing.{c.h} is now a propagator prop_probing.{c,h}, all corresponding parameters moved as well
6675 - the redcost separator sepa_redcost.{c.h} is now a propagator prop_redcost.{c,h}, all corresponding parameters moved as well
6676 - outsourced propAndSolve() method in solve.c which calls domain propagation and solving of the lp and relaxation
6677
6678- Statistic:
6679 - solutions which are given by the user from the outside are now marked by `#` in the output
6680 - the `Solving Time` is now spitted into presolving, solving and reading time
6681 - Presolvers section has new column `AddCons` which states the number of added constraint
6682 - Constraints section has new column named \#ResProp which show the number of resolve propagation calls of certain
6683 constraint handler
6684 - Constraint Timing section has a new column \#ResProp which states the time spend in resolve propagation method of the
6685 constraint handler
6686 - improved output of propagators in display statistics
6687 - new section `Propagator Timing` which shows the time spend in different callbacks of the propagator
6688 - rearranged first two columns of Propagators section; \#Propagate and \#ResProp stating the number of call for
6689 propagation and resolve propagation; the Time column is moved into the new section Propagator Timings
6690 - Constraints section has new column named `MaxNumber` which the maximum number of active constraint of a certain
6691 constraint handler
6692 - added two columns `Time-0-It` and `Calls-0-It` in the LP section which states the number of LP call and time spend for
6693 solving LPs with zero iterations (only refactorization)
6694 - The display of statistics for presolvers, propagators, constraints and LP solving has changed.
6695
6696Performance improvements
6697------------------------
6698
6699- Reorganized filtering process of separation storage (allows adding cuts for different solutions)
6700- Improved presolving for various constraint handlers
6701- Improved propagation methods for variable bound constraints
6702- Improved performance for quadratic constraints
6703- performance improvements in prop_vbounds
6704- child selection rules now get also applied when the relaxation value is equal to the bound changed in branching
6705- added dual reduction to cons_cumulative.c
6706- for continuous variables, the pseudo costs update and the pscost branching rule now use the same strategies for
6707 updating the pseudo costs and estimating the improvement in the LP bound
6708- only perform probing if the variables are locked
6709- performance and memory consumption improvements in xmlparse.c
6710- Improved knapsack cover cuts
6711- avoid very long separation times of LEWIs in cons_knapsack for very large minimal covers
6712- used SCIPallocMemoryArray() instead of SCIPallocBlockMemoryArray() which leads to fewer memory consumption in
6713 getLiftingSequence() in cons_knapsack, also improved cache use bei using an extra array instead blockmemory chunks
6714- switched FASTMIP from 1 to 2 for CPLEX and changed default pricing rule back to steepest edge pricing instead of
6715 quickstart steepest edge pricing
6716- made sorting method more robust
6717- LNS heuristics now use SCIPcopy() by default
6718- considering inactive variables in undercover heuristic; limiting effort for solving covering problem
6719- if during probing mode the LP relaxation is solved from scratch, e.g., when calling the shiftandpropagate heuristic
6720 before root node solving, then we clear the resulting LP state, since it might be a bad starting basis for the next
6721 solve of the LP relaxation (controlled by new parameter `lp/clearinitialprobinglp`)
6722- included LP simplifier into SoPlex LP interface, applied when solving from scratch (lpi_spx.cpp)
6723- new presolving steps in varbound constraint handler, tightening bounds, coefficients, sides and pairwise presolving
6724
6725Interface changes
6726-----------------
6727
6728- Miscellaneous:
6729 - The emphasis setting types now distinguish between plugin-type specific parameter settings (default, aggressive, fast, off),
6730 which are changed by SCIPsetHeuristics/Presolving/Separating(), and global emphasis settings (default, cpsolver, easycip,
6731 feasibility, hardlp, optimality, counter), which can be set using SCIPsetEmphasis().
6732
6733### New and changed callbacks
6734
6735- added propagator timings `SCIP_PROPTIMING_BEFORELP`, `SCIP_PROPTIMING_DURINGLPLOOP` and `SCIP_PROPTIMING_AFTERLPLOOP` for
6736 all propagation callbacks (see propagators and constraint handlers) which lead to calling the propagation methods of a
6737 propagator before the lp is solved, during the lp loop and after the lp solving loop
6738
6739- Conflict Analysis:
6740 - Added parameter `separate` to conflict handler callback method SCIP_DECL_CONFLICTEXEC() that defines whether the conflict
6741 constraint should be separated or not.
6742
6743- Constraint Handler:
6744 - The new constraint handler callback SCIP_DECL_CONSDELVARS() is called after variables were marked for deletion.
6745 This method is optional and only of interest if you are using SCIP as a branch-and-price framework. That means,
6746 you are generating new variables during the search. If you are not doing that just define the function pointer
6747 to be `NULL`.
6748 If this method gets implemented you should iterate over all constraints of the constraint handler and delete all
6749 variables that were marked for deletion by SCIPdelVar().
6750
6751- NLP Solver Interface:
6752 - The callbacks SCIP_DECL_NLPIGETSOLUTION() and SCIP_DECL_NLPISETINITIALGUESS() got new parameters to get/set values of
6753 dual variables.
6754 - The callback SCIP_DECL_NLPICOPY() now passes the block memory of the target SCIP as an additional parameter.
6755
6756- Presolving:
6757 - New parameters `isunbounded` and `isinfeasible` for presolving initialization (SCIP_DECL_CONSINITPRE(),
6758 SCIP_DECL_PRESOLINITPRE(), SCIP_DECL_PROPINITPRE()) and presolving deinitialization (SCIP_DECL_CONSEXITPRE(),
6759 SCIP_DECL_PRESOLEXITPRE(), SCIP_DECL_PROPEXITPRE()) callbacks of presolvers,
6760 constraint handlers and propagators, telling the callback whether the problem was already declared to be
6761 unbounded or infeasible. This allows to avoid expensive steps in these methods in case the problem is already
6762 solved, anyway.
6763
6764 Note, that the C++ methods
6765 - scip::ObjConshdlr::scip_presol() corresponding to SCIP_DECL_CONSPRESOL()
6766 - scip::ObjConshdlr::scip_initpre() corresponding to SCIP_DECL_CONSINITPRE()
6767 - scip::ObjPresol::scip_initpre() corresponding to SCIP_DECL_PRESOLINITPRE()
6768 - scip::ObjProp::scip_initpre() corresponding to SCIP_DECL_PROPINITPRE()
6769 - scip::ObjConshdlr::scip_exitpre() corresponding to SCIP_DECL_CONSEXITPRE()
6770 - scip::ObjPresol::scip_exitpre() corresponding to SCIP_DECL_PRESOLEXITPRE()
6771 - scip::ObjProp::scip_exitpre() corresponding to and SCIP_DECL_PROPEXITPRE()
6772 are virtual functions. That means, if you are not adding the new parameters, your code will still compile, but these methods are not executed.
6773 - Propagators are now also called in during presolving, this is supported by the new callback methods SCIP_DECL_PROPINITPRE(),
6774 SCIP_DECL_PROPEXITPRE(), and SCIP_DECL_PROPPRESOL().
6775 - The new parameters `nnewaddconss` and `naddconss` were added to the constraint handler callback method SCIP_DECL_CONSPRESOL()
6776 and the presolver callback method SCIP_DECL_PRESOLEXEC(). These parameters were also added to corresponding C++ wrapper
6777 class methods (scip_presol() in objconshdlr.h and scip_exec() in objpresol.h)
6778
6779- Problem Data:
6780 - The callback SCIP_DECL_PROBCOPY() got a new parameter `global` to indicate whether the global problem or a local version is copied.
6781
6782### Deleted and changed API functions
6783
6784- implemented SCIPlpiGetPrimalRay() in SoPlex interface that has become available with SoPlex version 1.5.0.2
6785- allowed calling SCIPgetRowSolActivity() in `SCIP_STAGE_SOLVED`, since LP is still available
6786- various extensions and modifications for expressions and expression trees (too much to state here)
6787- The result value `SCIP_NEWROUND` has been added, it allows a separator/constraint handler to start a new separation round
6788 (without previous calls to other separators/conshdlrs).
6789- SCIPcalcNodeselPriority() got a new parameter `branchdir`, which defines the type of branching that was performed: upwards, downwards, or fixed.
6790
6791- Constraint Handlers:
6792 - Method SCIPincludeQuadconsUpgrade() of quadratic constraint handler got new parameter `active` to indicate whether the upgrading method is active by default.
6793 - Method SCIPseparateRelaxedKnapsack() in knapsack constraint handler got new parameter `cutoff`, which is a pointer to store whether a cutoff was found.
6794
6795- Nonlinear expressions, relaxation, and solver interface:
6796 - SCIPcreateNLPSol() now creates a `SCIP_SOL` that is linked to the solution of the current NLP relaxation
6797 - Various types and functions dealing with polynomial expressions have been renamed to use the proper terms `monomial` and
6798 `polynomial` in nonlinear expressions (nlpi/∗expr*); results in many renamings of types, structs and methods.
6799 - The methods SCIPnlpGetObjective(), SCIPnlpGetSolVals(), and SCIPnlpGetVarSolVal() have been removed, use SCIPgetNLPObjval(),
6800 SCIPvarGetNLPSol() and SCIPcreateNLPSol() to retrieve NLP solution values instead.
6801 SCIPcreateNLPSol() now returns an error if NLP or NLP solution is not available
6802 - Removed methods SCIPmarkRequireNLP() and SCIPisNLPRequired(), because the NLP is now always constructed if nonlinearities
6803 are present.
6804 - SCIPgetNLP() has been removed and NLP-methods from pub_nlp.h have been moved to scip.h, which resulted in some renamings, too.
6805 - renamed SCIPexprtreeEvalSol() to SCIPevalExprtreeSol() and now located in scip.h.
6806 - renamed SCIPexprtreeEvalIntLocalBounds() to SCIPevalExprtreeLocalBounds() and now located in scip.h.
6807 - renamed SCIPexprtreeEvalIntGlobalBounds() to SCIPevalExprtreeGlobalBounds() and now located in scip.h.
6808 - The functions SCIPnlpiGetSolution() and SCIPnlpiSetInitialGuess() got additional arguments to get/set dual values.
6809 - The method SCIPgetNLPI() got a new parameter `nlpiproblem`, which is a pointer to store the NLP solver interface problem.
6810
6811- Timing:
6812 - SCIPincludeProp() got additional parameters to set the timing mask of the propagator and the new callbacks and parameters
6813 related to calling the propagator in presolving.
6814 - SCIPincludeConshdlr() got additional parameters to set the variable deletion callback function and the timing mask for
6815 propagation.
6816 - removed parameters timelimit and memorylimit from SCIPapplyRens()
6817 - The parameters `timelimit` and `memorylimit` were removed from SCIPapplyRens().
6818
6819- Problem Data:
6820 - The method SCIPcopyProb() got a new parameter `global` to indicate whether the global problem or a local version is copied.
6821
6822- Writing and Parsing Constraints:
6823 - The methods SCIPwriteVarName(), SCIPwriteVarsList(), and SCIPwriteVarsLinearsum() got a new boolean parameter `type`
6824 that indicates whether the variable type should be written or not.
6825 - The methods SCIPparseVarName() and SCIPparseVarsList() got a new output parameter `endptr` that is filled with the position
6826 where the parsing stopped.
6827 - The method SCIPwriteVarsList() got additionally a new parameter `delimiter` that defines the character which is used for delimitation.
6828
6829- Variables:
6830 - SCIPmarkDoNotMultaggrVar()/SCIPvarMarkDoNotMultaggr() now allow to mark negated and aggregated variables
6831 - SCIPgetVarCopy() got a new parameter `success` that will be FALSE if method is called after problem creation stage and no hash map is
6832 given or no image for the given variable is contained in the given hash map.
6833 - SCIPchgVarType() got an extra boolean parameter to store if infeasibility is recognized while upgrading a variable from continuous
6834 type to an integer type.
6835 - SCIPdelVar() got a new parameter `deleted`, which stores whether the variable was successfully marked to be deleted.
6836
6837### New API functions
6838
6839- information about the quality of the solution of an LP (currently the condition number of the basis matrix) can now be:
6840 + requested from the LPI (currently only available for CPLEX): methods SCIPlpiGetRealSolQuality() and
6841 + SCIPprintLPSolutionQuality() command display lpsolquality in interactive shell display column lpcond to show
6842 + estimate on condition number, if available
6843- SCIPround() and SCIPfeasRound() to round to nearest integer
6844- SCIPsortRealRealIntInt() and corresponding sorting/inserting/deleting methods in pub_misc.h and necessary defines in misc.c
6845- SCIPsortRealIntLong(), SCIPsortPtrPtrRealInt() and corresponding sorting/inserting/deleting methods in
6846 pub_misc.h and necessary defines in misc.c
6847- SCIPcomputeLPRelIntPoint() to compute relative interior point of the current LP
6848- SCIPstartSolvingTime() and SCIPstopSolvingTime() which can be used to start or stop the solving time clock
6849- SCIPstrToRealValue() and SCIPstrCopySection() in pub_misc.h; these methods can be used to convert a string
6850 into a `SCIP_Real` value and to copy a substring.
6851- SCIPgetBinvarRepresentatives() which gets binary variables that are equal to some given binary variables,
6852 and which are either active, fixed, or multi-aggregated, or the negated variables of active, fixed, or multi-aggregated variables
6853- SCIPhasPrimalRay() and SCIPgetPrimalRayVal() that return whether a primal ray is stored and which value a
6854 given variable has in the primal ray, respectively
6855- SCIPsetConsModifiable()
6856- SCIPsetParam() which is a generic parameter setter method, independent of the parameter type
6857- SCIPpropInitpre(), SCIPpropExitpre(), SCIPpropPresol() which initializes, exists and executes the presolving phase
6858- SCIProwGetAge() to access the age of a row (pub_lp.h/lp.c)
6859- SCIPsolGetOrigObj() in pub_sol.h which returns for a solution in the original problem space the objective value
6860- SCIPretransformSol() in scip.h that allows to retransform a solution to the original space
6861- SCIPlpiClearState() to LP interfaces for clearing basis information in the LP solver
6862- SCIPgetSubscipDepth() to access the depth of the current SCIP as a copied subproblem
6863- SCIPdebugAddSolVal() and SCIPdebugGetSolVal() to add/get values to/from a debug solution
6864- SCIPsepastoreRemoveInefficaciousCuts() to remove non-efficious cuts from the separation storage
6865
6866- Nodes:
6867 - SCIPnodeGetParent() to get parent node of a node
6868 - SCIPnodesSharePath() in pub_tree.h that determines whether two nodes are on the same leaf-root path
6869 - SCIPnodesGetCommonAncestor() in pub_tree.h that finds the common ancestor node for two given nodes
6870
6871- Read and Write:
6872 - SCIPgetReadingTime() which returns the time for reading in seconds
6873 - SCIPparseVarsLinearsum(), SCIPparseVarsPolynomial() and SCIPwriteVarsPolynomial() and for writing and
6874 parsing polynomials in constraint handler writing/parsing methods
6875
6876- Memory:
6877 - SCIPcreateMesshdlrPThreads() and SCIPfreeMesshdlrPThreads() for allocating and deleting necessary memory
6878 for message handlers for parallel pthread version
6879 - SCIPallocClearMemoryArray() and BMSallocClearMemoryArray() for allocating cleared memory arrays in scip.h and memory.h
6880
6881- Intervals:
6882 - SCIPintervalPowerScalarInverse() to solve an equation y = x^p for given bounds on y and scalar exponent p
6883 - SCIPintervalQuadBivar() to compute tight bounds on a bivariate quadratic form
6884 - SCIPintervalSolveBivariateQuadExpressionAllScalar() to compute tight bounds on the solutions of a bivariate quadratic equation
6885
6886- Variables:
6887 - SCIPcomputeVarCurrent{L,U}b{Local,Global}() to compute local or global lower or upper bounds of a
6888 multiaggregated variable from the bounds of the aggregation variables
6889 - SCIPbranchVarValNary() for n-ary variable branching
6890 - SCIPgetNegatedVars() which returns all negated variables for a given array of variables, if the negated
6891 variables are not existing yet, they will be created
6892 - SCIPgetNTotalVars() that returns the total number of created vars, icluding variables that were deleted in the meantime
6893 - SCIPvarGetHashkey(), SCIPvarIsHashkeyEq(), SCIPvarGetHashkeyVal() in pub_var.h which can be used for `SCIP_HASHTABLE` of variables
6894 - SCIPvarGetNBdchgInfosLb() and SCIPvarGetNBdchgInfosUb() in pub_var.h returning the number of lower or upper bound changes on the active path
6895 - SCIPvarGetBdchgInfoLb() and SCIPvarGetBdchgInfoUb() returning the bound change information at the given position
6896 - SCIPvarMarkDeletable() to mark a variable to be deletable completely from the problem (for
6897 branch-and-price); can only be called before the variable is added to the problem
6898 - SCIPvarMarkNotDeletable() that marks a variable to be non-deleteable (used within SCIP for forbidding
6899 deletion of variables contained in solution, LP bases, (multi)aggregation, ...)
6900 - SCIPvarIsDeletable() that returns whether a variable is marked to be deletable (each variable is per default non-deletable)
6901
6902- NLP:
6903 - SCIPgetNLPVarsNonlinearity() to get for each variable in the NLP the number of NLP rows in which this variable appears in a nonlinear way
6904 - SCIPnlrowGetDualsol(), SCIPgetNLPVarsLbDualsol(), SCIPgetNLPVarsUbDualsol() to retrieve dual values from an NLP solution
6905 - SCIPgetNLPFracVars() to get the fractional variables in an NLP solution
6906
6907- Propagator:
6908 - SCIPpropSetPresolPriority() which changes the presolving priority of a given propagator
1.16.1