SCIP 3.1.1

Features

use clock average to reduce number of system calls via timing/rareclockcheck parameter
added copy mechanism for conjunction constraints
added revised lpi_xprs for using XPRESS as LP solver

Performance improvements

improved solving of LPs in OBBT propagator
improved activity-delta computation and thereby propagation for linear constraints
improved memory management of proximity heuristic
disabled statistic timing in all subscips via new parameter timing/statistictiming

Interface changes

Deleted and changed API methods

renamed MIP matrix structure to SCIP_MATRIX
changed the numeric values for PRESOLTIMING flags
forbid to call SCIPfixVar() in SCIP_STAGE_PRESOLVED stage, which is not allowed since it calls SCIPchgVarLb/Ub()
rename SCIPdigraphGetNodeDatas() to SCIPdigraphGetNodeData(); SCIPdigraphSetNodeDatas() to SCIPdigraphSetNodeData()
rename array arcdatas in digraph to arcdata
SCIPapplyProximity() has an additional argument freesubscip, which causes the method to free the created subscip automatically at the end.
changes in clock type are now transferred to SoPlex
corrected wrong primal bound in statistics for unbounded problems

New API functions

SCIPhasPerformedPresolve() to check, e.g., whether LP duals are accessible
SCIPconvertRealTo[Long]Int() to convert reals that represent integers to [long] ints.
SCIPisDualfeasEQ() and related to perform checks w.r.t. to the dual feasibility tolerance
SCIPdeleteSubproblemProximity() to free proximity subproblem manually as external caller

Command line interface

added dialog for writing the finite solution (calling SCIPcreateFiniteSolCopy() before writing)

Interfaces to external software

AMPL interface now returns dual multipliers if problem is an LP and presolving was turned off

Changed parameters

changed default value of parameter heuristics/proximity/minimprove to 0.02; previous value was 0.25
changed default value of parameter heuristics/proximity/usefinallp to FALSE

New parameters

"timing/rareclockcheck" to call the system time less frequently, based on the current average time interval between two calls to SCIPsolveIsStopped(); the default value is FALSE
"timing/statistictiming" to enable/disable all timers for statistic output of SCIP; the default value is TRUE

Build system

Makefile

added Makefile support for cygwin 64 Bit
allow to turn off block and buffer memory by the makefile parameters NOBLKMEM, NOBUFMEM, NOBLKBUFMEM; also remove the now superfluous makefiles for noblkmem, nobufmem, noblkbufmem

Fixed bugs

fixed bug in cons_quadratic which leads to wrong min/max activities
fixed wrong conversion of reals representing negative integer values
in debug mode, SCIP checks that no NaN's are introduced in SCIPsolSetVal()
fixed bug in proximity heuristic which attempted to enter diving mode even at nodes without a constructed LP
fixed wrong pseudo cost updates during diving heuristic execution after backtracking
fixed bug 697 (and 699), calling SCIPsolve() after the problem was already solved and SCIPfreeSolve() was called now does nothing anymore
fixed memory leaks in case of erroneous parsing of constraints, e.g., non-linear constraints
added support for character '#' in variable names in old non-linear CIP format (i.e., names without "<lt;" and ">gt;")
fixed bug 702, removed too hard assert when casting too big values into SCIP_Longint
removed wrong break in cons_pseudoboolean
branching for continuous variables with unbounded intervals now takes "branching/clamp" into account
fixed bug in SCIPpermuteProb(), when called in transformed stage and non-active constraints exist
corrected copy of disjunction constraints
forbid aggregations with scalar smaller feastol or larger 1/feastol
fixed bug 683, not recognizing errors/segfaults especially in free stage of SCIP by improving the check scripts
fixed bug in presolving of abspower constraints that lead to wrong variable locks
fixed bug where quieting a message handler also disabled writing to files other than stdout
fixed bug 708, special case of implications led to a fixing
allow to call SCIPmarkConsPropagate() in INITPRESOLVE stage
fixed bug, variable bounds detected wrong infeasibility
another bug fix when computing the original variable sum of a given variable in SCIPvarGetOrigvarSum()
fixed bug in cons_varbound.c using the wrong constraint side for updating an upper bound
fixed missing memory allocation for node data in digraphs
allow to read numbers like "42856." in lp-format
fixed bug in heur_oneopt: avoid bound violations if shift value is negative due to infeasibilities
fixed setting solution value of multi-aggregated var in xml-solution case
fixed wrong output of status when an objective limit was imposed but not reached yet
fixed the rare case that branching was performed even though strong branching found global bound changes leading to an infeasible/objlimit LP
fixed bug that reaching a solution limit by beforenode heuristics lead to disregarding the current node if the optimization process was restarted later
fixed bug with reading '>gt;=1' indicator constraints in LP-files
fixed bug changing the variable type of an negated variable
use dual feasibility tolerance for comparisons regarding reduced costs
fixed bug with freeing problem: need to reset objective limit
fixed bug in presolve of cons_nonlinear: wrong constraint upgrades may have been performed due to outdated bound information in expression graph
fixed numerical troubles in SCIPcreateFiniteSolCopy()
fixed bug in SCIPpermuteProb(): if called before transforming the problem, data structures were not initialized yet
fixed bug in trysol heuristic not saving the best solution in maximization problems
fixed bug in aggregation procedure if two variables were of non-binary type but for one of the variables SCIPvarIsBinary() returned true
treat activities of pseudo solutions as invalid when containing positive and negative infinity contributions
fixed bug in cons_setppc, wrongly aggregating variables if dual-presolving was disabled
fixed bug that objective limit was not reset correctly during SCIPfreeTransform() for maximization problems
fixed bug in cons_sos1: locks and events were not initialized if constraint was added to transformed problem
fixed bug(?) in reader_mps: variables are now written in columns section even of they occur in no constraint and have an objective coefficient of 0 (otherwise, CPLEX and Gurobi cannot read the file)
fixed bug that hitting the time limit while solving a pure LP and then continuing the solving process lead to not solving the LP, but always creating a single child node until maximum depth is reached
fixed bug in reader_lp which created two indicator constraints with the same name to trigger an equality
fixed bug leading to an incorrect dual bound when solving probing LPs within a DURINGPRICINGLOOP heuristic
fixed bug in components presolver with handling of dual fixable variables: unboundedness was not detected, better handle components with single variables by dual fixing propagator
fixed bug in prop_dualfixing: don't fix variables to infinite values during solving
fixed bug in cons_setppc with dual presolving disabled
fixed sign of the dual multipliers returned by AMPL interfaces for maximization
fixed bug in GMI example: fractionality of slack variable is now computed correctly
issues in component solving by presol_components do not lead to stopping the overall process, anymore, the component is just disregarded
fixed bug when reading indicator constraints for linear constraints (equations/ranged rows) from MPS files
fixed LP interface of CPLEX: functions getBInv* return the correct sign of the coefficients.

SCIP 3.1.0

Features

new primal heuristics dual value
the rank of cuts is now stored and taken into account to improve numerical stability
new LNS heuristic called "proximity", which solves a problem in which a local branching constraint replaces the objective function which in turn is treated as additional constraint
new LP-based rounding heuristic (heur_randround) whose randomized rounding is biased towards the LP solution value; the heuristic uses the probing mode of SCIP to generate conflict clauses on the fractional variables
added breadth first search node selection
new node selection rule UCT which balances exploration and exploitation by considering node visits
added new dual presolving for setppc-constraints
changed dualfix presolver to propagator such that dual fixing can also be applied during repropagation of the root node
added upgrade from varbound constraints to set-packing constraints
added upgrade from bounddisjunction constraints to set-packing/logicor constraints
added two methods to iterate over a sparse solution (SCIP_SPARSESOLUTION), see pub_misc.h
added possibility to not set a cutoff bound in the LP solver (can be enabled by setting "lp/disablecutoff>gt; to TRUE)
cumulative constraint handler adds disjunctive constraints (cumulative with capacity 1) for all jobs which cannot be processed in parallel
added new clique extraction algorithm for linear constraints
added missing debugging solution check for cliques
the slack variables of indicator constraints can now be scaled
added redundancy check of sides of ranged row varbound constraint
added coefficient tightening for ranged row varbound constraint
added a data pointer to each node of the SCIP_DIGRAPH
all readers now take the global parameters "reading/dynamic{conss|cols|rows}" and "reading/initialconss" into account
XOR constraint handler can add two extended formulations (flow/asymmetric, parameter "addflowextended/addextendedform")
SCIPgetVarCopy() will now copy the original bounds when called for an original variable
added propagation method to cons_xor relying on Gaussian elimination, which can also produce feasible solutions
new branching rule "cloud branching" that considers several alternative LP optima
additional vbc output added: branching information is printed earlier and also for nodes which were cut off
added reader_pbm, which writes the constraint-variable incidence matrix in pbm format (possibly scaled to given size)
added possibility to separate a cutpool w.r.t. a given solution (instead of LP-solution)
added multi-aggregation for binary variables with at most two uplocks and two downlocks, which emerge from set- partitioning or set-packing constraints
added full-dual presolving step in setppc constraint handler
added upgrade from quadratic constraints to set-packing constraints
generalized the linking constraint handler
in verblevel SCIP_VERBLEVEL_FULL, the number of non-zeros will be output for the original and presolved model
new presolving step for tightening logicor constraints using implication and clique information
can now read and write CIP-files with (multi-)aggregated variables
added first implication detection in cons_linear
several new presolving steps for linear and knapsack constraints, using gcd information and many more
cons_indicator can now try to construct feasible solutions from a cover
reader_osil can now read SOS1 and SOS2 constraints
reader_lp and reader_mps are now able to write and-constraints in form of their (weak/strict) relaxation
added possibility to forbid upgrading of linear constraints
it is now possible to add an offset for the original problem instance, all original solutions will be initialized with this value and updated, when the offset is changed
added clique presolving for xor constraints
added upgrade of continuous variables to implicit variables for linear equations even if the coefficient is not equal to 1
added presolving using pairs of variable bound constraints that use the same variables
added support for strong branching with domain propagation in full strong and reliability pseudo cost branching
added strong branching with domain propagation support: in SCIPstartStrongbranch(), support for propagation can be enabled (uses the probing mode, some overhead compared to standard strong branching), after that SCIPgetVarStrongbranchWithPropagation() can be used to perform strong branching on a variable with previous domain propagation; similar to probing, valid bounds for variables are collected
strong branching with propagation can be enabled in fullstrong and relpscost branching rule
added possibility to store pricing norms of the LP solver (in addition to basis information) to speed up LP solving after a backtrack, e.g. in probing or strong branching with domain propagation
probing supports implicit binary variables
added scaling to computation of relative interior point in SCIPcomputeLPRelIntPoint()
added more presolving to cons_indicator, checking whether indicator/slack variables are aggregated
new initial constraints are now added to the LP before solving a probing LP
SoPlex (>gt;= 1.7.0.5) can compute condition number of current basis matrix via LP interface
a pricer can now return that no further pricing should be done but rather early branching, even if it added variables
dual solution can now be displayed for pure LPs when no presolving was performed
first implementation of parsing for nonlinear constraints in CIP format
added reading capability to GAMS reader (if compiling with GAMS=true, requires a GAMS system)
added capability of writing SOS1/2 constraints to GAMS reader (introduces extra variables and equations)
added presolve.{c,h} which should be used for all preprocessing mechanisms executed from within SCIP, corresponding to solve.{c,h} and also for presprocessing methods which can be called from different plugins or from the core to avoid code doubling
extended and corrected dual feasibility checks for LP solution (controlled by parameter "lp/checkdualfeas")
return error if variable should be fixed to infinity after presolving (LP-solvers do not handle this consistently)
LPI files (lpi*.[h|c]) all moved from src/scip to src/lpi
Statistic
- added average gap based on primal-dual integral to solution statistics; can be disabled via parameter "misc/calcintegral"
- the statistics now include the value of the first LP solved at the root node (without cuts)
- added new statistic which distinguishes between internal nodes and leaves which got processed
- new section "Root Node" in statistics, listing objective value, iterations and solving time for the first LP solved at the root node as well as final dual bound of the root node and LP iterations for processing the root node (those where listed in the "Solutions" section before, named "Root Dual Bound" and "Root Iterations")

Performance improvements

major improvements in pseudo-boolean constraint handler
many presolving improvements in constraint handlers
performance improvement in domain propagation by marking constraints for propagation
dual fixing presolver was turned into a propagator
added more constraint upgrading possibilities
allow multiaggregation of binary variables
strong branching LP solutions are checked for integrality
improved handling of initial constraints created during solving
improved LP reoptimization for branch-and-price applications
improved numerical stability checks for LP solution
disabled scaling in feasibility check of nonlinear constraint handlers
conflict consisting of exactly two binary variables will be handled as set-packing constraint instead of an logicor constraint and the corresponding clique information is globally added
improved methods SCIPlpiGetBInv{Row,Col,ACol} for row representation in SoPlex LP interface
fasten repropagation for set-packing and -partitioning constraints
shorten conflicts and deriving global boundchanges from conflicts
disabled multi-aggregation in linear constraint handler when coefficients differ too much
improved multi-aggregation in linear constraint handler when only one variable in the aggregation has infinity contribution
improved dual-presolving for setppc constraints in special cases
apply lowerbound provided by pricers already during pricing loop, stop pricing if the lower bound computed by pricing already exceeds the cutoff bound
improved performance of method SCIPsolRetransform() when called during presolving with many aggregations
minor presolving performance improvements in cons_logicor.c and cons_knapsack.c
added upgradability for implicit binary variable cases for linear constraints
improved performance of SCIPcliquelistDel(), SCIPcliquetableAdd(), SCIPcliquetableCleanup()
improved merging of and-constraints
faster feasibility check of LP solutions (controlled by parameters lp/checkprimfeas and lp/checkdualfeas)

Examples and applications

new textbook Gomory mixed integer cuts example

Interface changes

moved LP interfaces to separate directory src/lpi
removed all message length parameters in message.c and for printing error messages (not needed anymore)
added number of constraints which are marked for propagation to callback method consprop

New and changed callbacks

the HEUREXEC callback has a new parameter "nodeinfeasible" which denotes whether the current node was already detected to be infeasible
the PRICERREDCOST callback has a new parameter "stopearly", which is a bool pointer to store whether pricing should be stopped early although variables were generated and early branching should be performed

Deleted and changed API methods

SCIPgetLPBranchCands() can be used to retrieve the number of implicit integer variables with fractional LP solution value via an additional pointer; the corresponding implicit integer variables can be accessed together with their fractionalities and solution values in the same way as binary and integer variables before; the arrays are sorted such that binary and integer variables precede the implicit integer variables; the method SCIPbranchcandGetLPCands() has been modified in the same way
SCIPcalcMIR() gets an additional parameter "cutrank" which returns the rank of the aggregation; via SCIProwChgRank() the rank of a cut can be changed (default rank is 0)
SCIPcalcMIR() takes an additional parameter sidetypes to determine which side of the rows to use (relevant for ranged rows)
SCIPaddCut() has an additional parameter that determines whether the cut to be added is infeasible for local bounds
SCIPwriteMIP() has an additional parameter that allows to write removable rows as lazy constraints
SCIPstartStrongbranch() has a new parameter "propagate" to enable or disable propagation support for strong branching
SCIPgetConsCopy() now always captures the created constraint
SCIPgetLPObjval() now returns the LP value of the current (suboptimal) basis if the iteration limit is hit during LP solving (instead of -infinity); this value is not necessarily a valid dual bound and must not be used as such, but can be used as an objective estimate, e.g., if strong branching is simulated using the probing mode
SCIPparseVar(), SCIPvarParseOriginal() and SCIPvarParseTransformed() now return the end of the parsed string
removed parameter "normtype" from function SCIPcomputeLPRelIntPoint()

New API functions

the main output routine of message.c (bufferMessage - now handleMessage) has been rewritten: it now does not need a copy of the string to be output anymore, which makes the code much simpler (and also faster); it is passed a function pointer to the output function and uses it to directly output the (buffered) messages
added SCIPdebugCheckConss() to the debugging mechanism and therefore created a SCIP_SOL (in original space) in debug.c
new methods for the SCIP_QUEUE data structure in pub_misc.h, misc.c SCIPqueueCreate(), SCIPqueueFree(), SCIPqueueClear(), SCIPqueueInsert(), SCIPqueueRemove(), SCIPqueueFirst(), SCIPqueueIsEmpty(), SCIPqueueNElems()
added the possibility to copy the original problem via SCIPcopyOrig()
before copying solutions to the original solution candidate storage, infinite solution values can now be removed using SCIPcreateFiniteSolCopy()
SCIPwriteCliqueGraph() to scip.{c,h} to write the clique graph in GML format into a given file
SCIPsortLongPtrRealBool(), SCIPsortLongPtrRealRealBool(), SCIPsortLongPtrRealRealIntBool() and corresponding methods for sorting, insertion and deletion
SCIPcreateFiniteSolCopy() which creates a copy of a solution, thereby trying to reduce the solution value of variables which were fixed to infinite to the smallest feasible value
SCIPapplyProbingVar() in prop_probing.h
SCIPadjustImplicitSolVals() which sets implicit integer variables to an integer value in a given solution without deteriorating its objective value
SCIPconshdlrIncNCutsFound(), SCIPsepaIncNCutsFound() and SCIPsepaIncNCutsFoundAtNode() to increase the number of found cuts
SCIPgetFirstLPTime() to return the time needed to solve the first LP of the root node
SCIPshrinkDisjunctiveVarSet(), which takes an set of variables with corresponding bounds and boundtypes, and tries to derive global boundchanges and also to shorten this set of variables by using cliqe, implication and variable bound information
SCIPgetFirstLP{Dual/Lower}boundRoot() which return the value of the first LP solved at the root node
SCIPgetNRootFirstLPIterations() which returns the number of LP iterations for the first LP solved at the root node
SCIPstoreSolutionGap() in scip.c, to store the gap when the first and last solution is found
SCIPcopyOrig(), SCIPcopyOrigProb(), SCIPcopyOrigVars() and SCIPcopyOrigConss() which allow to copy the complete original problem, the problem data, variables and constraints, respectively
SCIPchgRowLhsDive() and SCIPchgRowRhsDive() that allow to change the sides of a row during diving
SCIPselectVarStrongBranching() to get the variable that fullstrongbranching would select
SCIPseparateSolCutpool() to separate a cutpool w.r.t. a given solution
SCIPdoNotMultaggr() returning whether multi-aggregation is completely disabled
SCIPconsIsMarkedPropagate() to ask whether a constraint was explicitly added for propagation
SCIPaddOrigObjoffset() in scip.{c,h} which adds a value to the offset in original space and updates all orignal solutions correspondingly
SCIPgmlWriteNodeWeight() to write node weights
SCIPwriteCliqueGraph() which allows to write a graph with node weights for fractional variables
SCIPconsAddUpgradeLocks() and SCIPconsGetNUpgradeLocks() to either add/decrease the counter on upgrade-locks on a constraint or get the current number of upgrade-locks
SCIPlpiGetNorms(), SCIPlpiSetNorms() and SCIPlpiFreeNorms() for getting the LP pricing norms from the LP solver, loading them back into the solver and freeing the data
SCIPgetNCheckConss() in scip.{c,h}
SCIPcopyImplicationsCliques() that copies implications and cliques

Command line interface

allow dialog option to write clique graph
dual solution values can now be obtained in the interactive shell after solving a pure LP without presolving

Interfaces to external software

new SoPlex 2.0 interface, can be enabled with LPS=spx2
add support for SOS1 and SOS2 constraints to AMPL interface (see interfaces/check/testset/SOS/sos?a.mod for example)
added copy of GAMS interface from COIN-OR/GAMSlinks project; GAMS-reader in SCIP can now read model instances from .gms files
beta version of a python interface for the scipoptsuite is now available under interfaces/python
beta version of a Java native interface is now available under interfaces/jni

Changed parameters

parameter "branching/scorefunction" has new value 'q' for for 'q'uotient branching score function
changed type of parameters "constraints/bivariate/scaling", "constraints/quadratic/scaling", "constraints/soc/scaling" from boolean to character
changed default for "constraints/{abspower,bivariate,nonlinear,quadratic,soc}/scaling" to off
replaced parameter "lp/checkfeas" by two parameters "lp/checkprimfeas" and "lp/checkdualfeas" to decide on primal and dual feasibility checks individually
removed all local parameters "reading/(READER)/dynamic{conss|cols|rows}" and replaced them by global parameters "reading/dynamic{conss|cols|rows}"
changed default value of parameter numerics/dualfeastol to 1e-7 for safer dual bounds from LP solver
changed default max coefficient for big-M constraint to be initial from 1e6 to 1e9
changed default value of gomory cut separation parameter "separating/gomory/maxrank" from 0 to 3, to take also gomory cuts that could not be scaled to integral coefficients, with maximal rank 3 into account
new possible values for parameter "heuristics/shiftandpropagate/sortkey" for sorting variables w.r.t. their norm, default changed from 'u' to 'v', which means sorting downwards by violations
remove parameter "separating/closecuts/relintnormtype"

New parameters

"branching/checksol" and "branching/heursbsol" to specify whether the strong branching LP solution should be checked for feasibility and whether a simple rounding heuristic should be run on this solution
"branching/firstsbchild" and "branching/forceall" to specify the first child node to be investigated during strong branching ('u'p, 'd'down, 'a'uto) and whether always both children should be solved (only for strong branching with domain propagation, per default, the second child is not looked at when the first is infeasible)
"conflict/fullshortenconflict" to decide whether we want to stop shortening a conflict set, when no global bound changes can be found anymore
"conflict/maxvarsdetectimpliedbounds" to decide whether the a valid conflict of what maximal length will be used to derive global bound changes
"constraints/{linear,knapsack}/detectcutoffbound" and "constraints/{linear,knapsack}/detectlowerbound" to enable/disable detection of constraint parallel to the objective function that will add an cutoffbound or an lowerbound respectively and these constraints will be prevented from entering the LP
"constraints/and/upgraderesultant" to upgrade resultants of and constraints from binary to implicit binary variables, default is TRUE
"constraints/abspower/scaling" and "constraints/nonlinear/scaling"
"constraints/indicator/scaleslackvar" for scaling of the slack variable in indicator constraints
"constraints/indicator/trysolfromcover" for trying to construct a feasible solution from a cover
"constraints/linear/checkrelmaxabs" for checking linear constraints with a side of 0.0 relative to
"constraints/linear/detectpartialobjective" to enable/disable the detection of sub-equations of the objective function
"constraints/logicor/strengthen", should pairwise constraint comparison try to strengthen constraints by removing superflous non-zeros?
"constraints/xor/addextendedform" to add an extended formulation in XOR-constraints
"constraints/xor/addflowextended" to add use the extended flow formulation in XOR-constraints
"heuristics/<lt;heurname>gt;/lplimfac" for LNS heuristics to limit the number of LPs solved in a subproblem the maximum absolute value in the activity instead of 1.0
"heuristics/shiftandpropagate/fixbinlocks" for fixing binary variables with no locks in one direction to the corresponding bound
"heuristics/shiftandpropagate/collectstats" which decides whether variable statistics are collected
"heuristics/shiftandpropagate/impliscontinuous" to decide whether implicit integer variables are treated as continuous variables
"heuristics/shiftandpropagate/preferbinaries" and "heuristics/shiftandpropagate/stopafterfeasible", which decide whether binaries should be shifted first and the shifting should be stopped when no violations are left
"lp/disablecutoff" to toggle usage of LP cutoff bound (0: enabled, 1: disabled, 2: auto = disabled if pricers are used)
"misc/calcintegral" (default TRUE) to trigger calculation of primal-dual integral
"misc/finitesolutionstore" to switch whether infinite fixings should be removed from solutions before copying them to the original solution store
"misc/permuteconss" and "misc/permutevars" to control whether variables and/or constraints should be permuted, if permutationseed != -1
"presolving/components/feastolfactor" to increase the feasibility tolerance in all sub-SCIPs, when solving a component
"propagating/obbt/conditionlimit" to discard instable LP bases
"reading/(READER)/initialconss" that determines whether model constraints are initial
"reading/cipreader/writefixedvars" for disabling printing of fixed variables in CIP format
"reading/lpreader/aggrlinearization-ands" and "reading/mpsreader/aggrlinearization-ands" to enable/disable the printing of the weak or strict relaxation of and-constraints in LP and MPS format, respectively
"reading/lpreader/linearize-and-constraints" and "reading/mpsreader/linearize-and-constraints" to allow and-constraints to be linearized when printing in LP and MPS format, respectively
"separating/feastolfac" to allow dynamic decrease of relaxation feasibility tolerance depending on feasibility to applied cuts, i.e., allow relaxation solutions to have a primal infeasibility of at most this factor times the infeasibility of applied cuts
"separating/gomory/sidetypebasis" to decide whether the sides of ranged rows should be determined from the basis status
"separating/oddcycle/cutthreshold" to run odd cycle separation if not enough cuts have been found
"separating/zerohalf/delayedcuts" to use the delayed cutpool for the zerohalf separator
"write/allconss" to enable that all constraints are written
"write/genericnamesoffset" when writing a generic problem to define an offset on the variable numbering

Data structures

new data structure for (circular) queues (SCIP_QUEUE)
hash tables will now increase dynamically

Testing

added McNemar tests and Wilcoxon signed rank tests to cmpres.awk evaluation scripts
added passing MEM option of testgams(cluster) target as workspace option to GAMS jobs
extended test scripts by statistical tests

Build system

Makefile

default flag for ZIMPL is now "auto", which means that it is built if and only if GMP is available (GMP=true)
fixed make install for older Mac systems where install command does not have option -t
dropped support for Ipopt <lt; 3.10

Fixed bugs

fixed bug when adding (global) clique, implications or variable bound information in solving stage that lead to global bound changes which contradict local bounds and therefore need to be stored as pending bound changes
unlinking a solution now copies solution values smaller than SCIPepsilon() avoiding some feasible solution in the transformed problem to be infeasible in the original problem
fixed bug when flushing the warning buffer when SCIP is closed
fixed wrong strong branching results in lpi_grb.c and an invalid write
fixed wrong presolving finished status which sometimes occurred when the time limit was hit during presolve
fixed several bugs where variables or constraints were not freed correctly
fixed minor bugs in presolving in cons_setppc.c and cons_logicor.c
do not multi-aggregate variables if the constant would be a huge value in order to avoid numerical troubles
fixed bug with infinite multi-aggregation constants
fixed wrong bound calculation in sepa_rapidlearning
fixed bug when a bound change contradicts a local bound and is stored as pending, but the contradicting local bound becomes global afterwards (–>gt; node where pending bound change is valid can be cut off)
fixed bug w.r.t. changing the variable branching priority beyond the problem stage
fixed statistics bug: externally given solutions and new solutions found while transforming existing ones are now listed in line "other solutions" of primal heuristics statistics
fixed memory bug in reader_mps
fixed output of aggregated variables in indicator constraints in lp and mps-format
fixed bug in reading indicator constraints in mps-format
improved handling of initial constraints: constraints which are initial, but added during the search to an already treated node are kept and added to the LP at every node where they are active
fixed bug where a limit on presolving rounds was exceeded by 1
fixed bug that lead to resolving the LP after diving instead of restoring the buffered solution
fixed rare bug with conflict analysis and LP/LPI having different states after diving
fixed bug in genvbounds propagator occurring when objective offset or scale changes after a restart
fixed bug in flowcover separator to exclude unconstrained rows in aggregation
fixed bug in prop_dualfix w.r.t. to fixing of variables to infinity after presolving
fixed bug in random generators SCIPgetRandomInt() and SCIPgetRandomReal() for large intervals
fixed bug in genvbounds propagator by replacing non-active variables on right-hand side after presolving
nonlinear readers now create auxiliary objective variables and constraints always as initial and not removable in order to avoid unbounded LPs due to loose variables with infinite best bound
fixed bug in cons_superindicator concerning names of upgraded constraints
fixed several bugs in lpi_grb
fixed bug in sepa_cgmip computeObjWeightSize() w.r.t. equal sized rows
fixed several minor bugs with handling of memory when writing aggregated variables (reader_lp, reader_mps)
fixed minor bug in cons_linear w.r.t. disabled presolving
fixed bug in handling max-function in ampl interface; added support for min-function
fixed bug in cons_indicator with trying to create solution in problem stage
fixed bug in cons_orbitope with fixing upper right triangle in non-root nodes
fixed bug in reader_lp when writing bilinear terms (product sign was missing)
allow again branching on continuous variables with huge bounds
make sure that bound changes of negated original variables are correct

Miscellaneous

new SCIP Optimization Suite homepages