Detailed Description

variable pricer for the vertex coloring problem

Author: Gerald Gamrath; Rolf van der Hulst

This file implements the pricer for the coloring algorithm.

It computes maximal stable sets in the current graph whose corresponding variables can improve the current LP solution. This is done by computing a maximum weighted stable set in the current graph with dual-variables of the node constraints as weights. A variable can improve the solution, if the weight of the corresponding stable set is larger than 1, since it then has negative reduced costs, which are given by (1 - weight of the set).

The pricer first tries to compute such a stable set using a a greedy-method. If it fails, the tclique-algorithm is used on the complementary graph. This is a branch-and-bound based algorithm for maximal cliques, included in SCIP. In this case, not only the best solution is added to the LP, but also all other stable sets found during the branch-and-bound process that could improve the current LP solution are added, limited to a maximal number that can be changed by a parameter.

Definition in file pricer_coloring.c.

#include <assert.h>
#include <string.h>
#include "pricer_coloring.h"
#include "reader_col.h"
#include "cons_storeGraph.h"
#include <stdio.h>
#include <stdlib.h>

Go to the source code of this file.

Macros
#define	PRICER_NAME "coloring"

#define	PRICER_DESC "pricer for coloring"

#define	PRICER_PRIORITY 5000000

#define	PRICER_DELAY TRUE /* only call pricer if all problem variables have non-negative reduced costs */

#define	MAXDNOM 10000LL

#define	MINDELTA 1e-12

#define	MAXDELTA 1e-09

#define	DEFAULT_MAXVARSROUND 1

#define	DEFAULT_USETCLIQUE TRUE

#define	DEFAULT_USEGREEDY TRUE

#define	DEFAULT_ONLYBEST FALSE

#define	DEFAULT_MAXROUNDSROOT -1

#define	DEFAULT_MAXROUNDSNODE -1

#define	DEFAULT_MAXTCLIQUENODES INT_MAX

Functions
static SCIP_Bool	hasUncoloredNode (TCLIQUE_GRAPH graph, SCIP_Bool colored)

static SCIP_RETCODE	sortNodes (SCIP scip, SCIP_Real weights, int nnodes, int *sortednodes)

static SCIP_RETCODE	greedyStableSet (SCIP scip, TCLIQUE_GRAPH graph, SCIP_Bool colored, int maxstablesetnodes, int *nmaxstablesetnodes)

static SCIP_RETCODE	calculateScalingValue (SCIP_PRICERDATA *pricerdata, int nnodes)

static TCLIQUE_WEIGHT	getScaledDualWeight (SCIP_Real val, SCIP_Real scalefactor, SCIP_Real mindelta)

static	TCLIQUE_NEWSOL (tcliqueNewsolPricer)

static	SCIP_DECL_PRICERCOPY (pricerCopyColoring)

static	SCIP_DECL_PRICERFREE (pricerFreeColoring)

static	SCIP_DECL_PRICERINITSOL (pricerInitsolColoring)

static	SCIP_DECL_PRICEREXITSOL (pricerExitsolColoring)

static	SCIP_DECL_PRICERREDCOST (pricerRedcostColoring)

static	SCIP_DECL_PRICERFARKAS (pricerFarkasColoring)

static	SCIP_DECL_PARAMCHGD (paramChgdMaxvarsround)

SCIP_RETCODE	SCIPincludePricerColoring (SCIP *scip)

Macro Definition Documentation

◆ PRICER_NAME

#define PRICER_NAME "coloring"

Definition at line 57 of file pricer_coloring.c.

◆ PRICER_DESC

#define PRICER_DESC "pricer for coloring"

Definition at line 58 of file pricer_coloring.c.

◆ PRICER_PRIORITY

#define PRICER_PRIORITY 5000000

Definition at line 59 of file pricer_coloring.c.

◆ PRICER_DELAY

#define PRICER_DELAY TRUE /* only call pricer if all problem variables have non-negative reduced costs */

Definition at line 60 of file pricer_coloring.c.

◆ MAXDNOM

#define MAXDNOM 10000LL

Definition at line 63 of file pricer_coloring.c.

◆ MINDELTA

#define MINDELTA 1e-12

Definition at line 64 of file pricer_coloring.c.

◆ MAXDELTA

#define MAXDELTA 1e-09

Definition at line 65 of file pricer_coloring.c.

◆ DEFAULT_MAXVARSROUND

#define DEFAULT_MAXVARSROUND 1

Definition at line 69 of file pricer_coloring.c.

◆ DEFAULT_USETCLIQUE

#define DEFAULT_USETCLIQUE TRUE

Definition at line 70 of file pricer_coloring.c.

◆ DEFAULT_USEGREEDY

#define DEFAULT_USEGREEDY TRUE

Definition at line 71 of file pricer_coloring.c.

◆ DEFAULT_ONLYBEST

#define DEFAULT_ONLYBEST FALSE

Definition at line 72 of file pricer_coloring.c.

◆ DEFAULT_MAXROUNDSROOT

#define DEFAULT_MAXROUNDSROOT -1

Definition at line 73 of file pricer_coloring.c.

◆ DEFAULT_MAXROUNDSNODE

#define DEFAULT_MAXROUNDSNODE -1

Definition at line 74 of file pricer_coloring.c.

◆ DEFAULT_MAXTCLIQUENODES

#define DEFAULT_MAXTCLIQUENODES INT_MAX

Definition at line 75 of file pricer_coloring.c.

Function Documentation

◆ hasUncoloredNode()

static SCIP_Bool hasUncoloredNode	(	TCLIQUE_GRAPH *	graph,
		SCIP_Bool *	colored
	)

static

returns whether the graph has an uncolored node

Parameters

graph	the graph that should be colored
colored	array of booleans, colored[i] == TRUE iff node i is colored

Definition at line 117 of file pricer_coloring.c.

References FALSE, NULL, and TRUE.

Referenced by SCIP_DECL_PRICERFARKAS().

◆ sortNodes()

static SCIP_RETCODE sortNodes	(	SCIP *	scip,
		SCIP_Real *	weights,
		int	nnodes,
		int *	sortednodes
	)

static

sorts the nodes from 0 to nnodes-1 w.r.t. the given weights

Parameters

scip	SCIP data structure
weights	the weights for sorting
nnodes	the number of nodes
sortednodes	the array that will be overwritten with the sorted node numbers

Definition at line 140 of file pricer_coloring.c.

References nnodes, NULL, SCIP_CALL, SCIP_OKAY, SCIP_Real, SCIPallocBufferArray, SCIPfreeBufferArray, and SCIPsortDownRealInt().

Referenced by SCIP_DECL_PRICERREDCOST().

◆ greedyStableSet()

static SCIP_RETCODE greedyStableSet	(	SCIP *	scip,
		TCLIQUE_GRAPH *	graph,
		SCIP_Bool *	colored,
		int *	maxstablesetnodes,
		int *	nmaxstablesetnodes
	)

static

computes a stable set with a greedy-method. attention: the weight of the maximum stable set is not computed!

Parameters

scip	SCIP data structure
graph	pointer to graph data structure
colored	array for marking yet colored nodes
maxstablesetnodes	pointer to store nodes of the maximum weight stableset
nmaxstablesetnodes	pointer to store number of nodes in the maximum weight stableset

Definition at line 170 of file pricer_coloring.c.

References FALSE, nnodes, NULL, SCIP_Bool, SCIP_CALL, SCIP_OKAY, SCIP_Real, SCIPallocBufferArray, SCIPfreeBufferArray, SCIPsortDownRealInt(), tcliqueGetDegrees(), and TRUE.

Referenced by SCIP_DECL_PRICERFARKAS().

◆ calculateScalingValue()

static SCIP_RETCODE calculateScalingValue	(	SCIP_PRICERDATA *	pricerdata,
		int	nnodes
	)

static

Calculates a good scalar value to use in order to scale the dual weights to integer values without large loss of precision

Parameters

pricerdata	pricer data
nnodes	number of nodes

Definition at line 243 of file pricer_coloring.c.

References MAXDELTA, MAXDNOM, MINDELTA, nnodes, SCIP_Bool, SCIP_CALL, SCIP_OKAY, SCIP_Real, and SCIPcalcIntegralScalar().

Referenced by SCIP_DECL_PRICERREDCOST().

◆ getScaledDualWeight()

static TCLIQUE_WEIGHT getScaledDualWeight	(	SCIP_Real	val,
		SCIP_Real	scalefactor,
		SCIP_Real	mindelta
	)

static

get scaled weight

Parameters

val	value to be scaled
scalefactor	scaling factor
mindelta	minimal delta value

Definition at line 276 of file pricer_coloring.c.

References EPSCEIL, EPSFLOOR, SCIP_Real, and SCIPrelDiff().

Referenced by SCIP_DECL_PRICERREDCOST().

◆ TCLIQUE_NEWSOL()

static TCLIQUE_NEWSOL ( tcliqueNewsolPricer )

static

generates improving variables using a stable set found by the algorithm for maximum weight clique, decides whether to stop generating cliques with the algorithm for maximum weight clique

Definition at line 303 of file pricer_coloring.c.

References COLORprobStableSetIsNew(), FALSE, NULL, and TRUE.

◆ SCIP_DECL_PRICERCOPY()

static SCIP_DECL_PRICERCOPY ( pricerCopyColoring )

static

copy method for pricer plugins (called when SCIP copies plugins)

Definition at line 349 of file pricer_coloring.c.

References NULL, PRICER_NAME, SCIP_OKAY, and SCIPpricerGetName().

◆ SCIP_DECL_PRICERFREE()

static SCIP_DECL_PRICERFREE ( pricerFreeColoring )

static

destructor of variable pricer to free user data (called when SCIP is exiting)

Definition at line 361 of file pricer_coloring.c.

References NULL, SCIP_OKAY, SCIPfreeBlockMemory, SCIPpricerGetData(), and SCIPpricerSetData().

◆ SCIP_DECL_PRICERINITSOL()

static SCIP_DECL_PRICERINITSOL ( pricerInitsolColoring )

static

solving process initialization method of variable pricer (called when branch and bound process is about to begin)

Definition at line 384 of file pricer_coloring.c.

References COLORprobGetNNodes(), COLORprobGetNStableSets(), MAX, NULL, SCIP_CALL, SCIP_OKAY, SCIPallocBlockMemoryArray, SCIPpricerGetData(), and SCIPsetIntParam().

◆ SCIP_DECL_PRICEREXITSOL()

static SCIP_DECL_PRICEREXITSOL ( pricerExitsolColoring )

static

solving process deinitialization method of variable pricer (called before branch and bound process data is freed)

Definition at line 410 of file pricer_coloring.c.

References COLORprobGetNNodes(), NULL, SCIP_OKAY, SCIPfreeBlockMemoryArray, and SCIPpricerGetData().

◆ SCIP_DECL_PRICERREDCOST()

static SCIP_DECL_PRICERREDCOST ( pricerRedcostColoring )

static

reduced cost pricing method of variable pricer for feasible LPs

Definition at line 438 of file pricer_coloring.c.

References calculateScalingValue(), COLORconsGetComplementaryGraph(), COLORconsGetCurrentGraph(), COLORprobAddNewStableSet(), COLORprobAddVarForStableSet(), COLORprobGetConstraints(), COLORprobGetNStableSets(), COLORprobStableSetIsNew(), FALSE, getScaledDualWeight(), MAX, MIN, MINDELTA, nnodes, NULL, TCLIQUE_Data::scip, SCIP_Bool, SCIP_CALL, SCIP_DIDNOTRUN, SCIP_LPSOLSTAT_OPTIMAL, SCIP_OKAY, SCIP_Real, SCIP_SUCCESS, SCIP_VARTYPE_BINARY, SCIPaddCoefSetppc(), SCIPaddPricedVar(), SCIPallocBufferArray, SCIPchgVarUbLazy(), SCIPcreateVar(), SCIPdebugMessage, SCIPfreeBufferArray, SCIPgetCurrentNode(), SCIPgetDualsolSetppc(), SCIPgetLPObjval(), SCIPgetLPSolstat(), SCIPgetNVars(), SCIPinfinity(), SCIPisFeasGT(), SCIPpricerGetData(), SCIPupdateLocalLowerbound(), SCIPvarMarkDeletable(), sortNodes(), TCLIQUE_OPTIMAL, TCLIQUE_USERABORT, tcliqueChangeWeight(), tcliqueMaxClique(), and TRUE.

◆ SCIP_DECL_PRICERFARKAS()

static SCIP_DECL_PRICERFARKAS ( pricerFarkasColoring )

static

farkas pricing method of variable pricer for infeasible LPs

Definition at line 707 of file pricer_coloring.c.

References BMSclearMemoryArray, COLORconsGetCurrentGraph(), COLORprobAddNewStableSet(), COLORprobAddVarForStableSet(), COLORprobGetConstraints(), COLORprobGetNNodes(), COLORprobGetStableSets(), COLORprobGetVarForStableSet(), greedyStableSet(), hasUncoloredNode(), nnodes, NULL, SCIP_Bool, SCIP_CALL, SCIP_OKAY, SCIP_VARTYPE_BINARY, SCIPaddCoefSetppc(), SCIPaddPricedVar(), SCIPallocBufferArray, SCIPchgVarUbLazy(), SCIPcreateVar(), SCIPfreeBufferArray, SCIPgetCurrentNode(), SCIPgetNNodes(), SCIPgetRootNode(), SCIPisFeasZero(), SCIPsortDownInt(), SCIPvarGetUbLocal(), SCIPvarIsInLP(), SCIPvarMarkDeletable(), and TRUE.

◆ SCIP_DECL_PARAMCHGD()

static SCIP_DECL_PARAMCHGD ( paramChgdMaxvarsround )

static

method to call, when the maximal number of variables priced in each round is changed

Definition at line 796 of file pricer_coloring.c.

References COLORprobGetNNodes(), NULL, SCIP_CALL, SCIP_OKAY, SCIPallocBlockMemoryArray, SCIPdebugMessage, SCIPfreeBlockMemoryArray, and SCIPparamGetData().

◆ SCIPincludePricerColoring()

SCIP_RETCODE SCIPincludePricerColoring ( SCIP * scip )

creates the coloring variable pricer and includes it in SCIP

Parameters

scip	SCIP data structure

Definition at line 849 of file pricer_coloring.c.

References DEFAULT_MAXROUNDSNODE, DEFAULT_MAXROUNDSROOT, DEFAULT_MAXTCLIQUENODES, DEFAULT_MAXVARSROUND, DEFAULT_ONLYBEST, DEFAULT_USEGREEDY, DEFAULT_USETCLIQUE, FALSE, NULL, PRICER_DELAY, PRICER_DESC, PRICER_NAME, PRICER_PRIORITY, SCIP_CALL, SCIP_OKAY, SCIPaddBoolParam(), SCIPaddIntParam(), SCIPallocBlockMemory, SCIPincludePricerBasic(), SCIPsetPricerCopy(), SCIPsetPricerExitsol(), SCIPsetPricerFree(), SCIPsetPricerInitsol(), and TRUE.

Referenced by SCIPincludeColoringPlugins().

SCIP

Detailed Description

Macros

Functions

Macro Definition Documentation

◆ PRICER_NAME

◆ PRICER_DESC

◆ PRICER_PRIORITY

◆ PRICER_DELAY

◆ MAXDNOM

◆ MINDELTA

◆ MAXDELTA

◆ DEFAULT_MAXVARSROUND

◆ DEFAULT_USETCLIQUE

◆ DEFAULT_USEGREEDY

◆ DEFAULT_ONLYBEST

◆ DEFAULT_MAXROUNDSROOT

◆ DEFAULT_MAXROUNDSNODE

◆ DEFAULT_MAXTCLIQUENODES

Function Documentation

◆ hasUncoloredNode()

◆ sortNodes()

◆ greedyStableSet()

◆ calculateScalingValue()

◆ getScaledDualWeight()

◆ TCLIQUE_NEWSOL()

◆ SCIP_DECL_PRICERCOPY()

◆ SCIP_DECL_PRICERFREE()

◆ SCIP_DECL_PRICERINITSOL()

◆ SCIP_DECL_PRICEREXITSOL()

◆ SCIP_DECL_PRICERREDCOST()

◆ SCIP_DECL_PRICERFARKAS()

◆ SCIP_DECL_PARAMCHGD()

◆ SCIPincludePricerColoring()