SCIP
Solving Constraint Integer Programs
presol_dualsparsify.h File Reference
Detailed Description
cancel nonzeros of the constraint matrix based on the columns
This presolver attempts to cancel non-zero entries of the constraint matrix by adding scaled columns to other columns.
In more detail, for two columns A_{j.} and A_{k.}, suppose for a given value s, we have
| A_{j.} | - | A_{j.} - s*A_{k.} | > eta,
where eta is an nonnegative integer. Then we introduce a new variable y := s*x_j + x_k and aggregate the variable x_k = y - s*x_j. After aggregation, the column of the variable x_j is A_{j.} + s*A_{j.} which is sparser than A_{j.}. In the case that x_k is no implied free variable, we need to add a new constraint l_k <= y - weight*x_j <= u_k into the problem to keep the bounds constraints of variable x_k.
Further information can be found in Chen et al. "Two-row and two-column mixed-integer presolve using hasing-based pairing methods".
Definition in file presol_dualsparsify.h.
Go to the source code of this file.
Functions | |
| SCIP_EXPORT SCIP_RETCODE | SCIPincludePresolDualsparsify (SCIP *scip) |
Function Documentation
◆ SCIPincludePresolDualsparsify()
| SCIP_EXPORT SCIP_RETCODE SCIPincludePresolDualsparsify | ( | SCIP * | scip | ) |
creates the dual sparsify presolver and includes it in SCIP
creates the dualsparsify presolver and includes it in SCIP
- Parameters
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scip SCIP data structure
Definition at line 1745 of file presol_dualsparsify.c.
References DEFAULT_ENABLECOPY, DEFAULT_MAX_BIN_FILLIN, DEFAULT_MAX_CONT_FILLIN, DEFAULT_MAX_INT_FILLIN, DEFAULT_MAXCONSIDEREDNONZEROS, DEFAULT_MAXRETRIEVEFAC, DEFAULT_MINELIMINATEDNONZEROS, DEFAULT_PRESERVEGOODLOCKS, DEFAULT_PRESERVEINTCOEFS, DEFAULT_WAITINGFAC, FALSE, NULL, PRESOL_DESC, PRESOL_MAXROUNDS, PRESOL_NAME, PRESOL_PRIORITY, PRESOL_TIMING, SCIP_CALL, SCIP_OKAY, SCIP_REAL_MAX, SCIPaddBoolParam(), SCIPaddIntParam(), SCIPaddRealParam(), SCIPallocBlockMemory, SCIPincludePresolBasic(), SCIPsetPresolCopy(), SCIPsetPresolFree(), SCIPsetPresolInit(), and TRUE.
Referenced by SCIP_DECL_PRESOLCOPY(), and SCIPincludeDefaultPlugins().