Detailed Description

heuristic that tries to solve the problem without objective. In Gurobi, this heuristic is known as "Hail Mary"

Author: Timo Berthold

#include <assert.h>
#include <string.h>
#include "scip/heur_zeroobj.h"
#include "scip/cons_linear.h"

Macros
#define	HEUR_NAME "zeroobj"

#define	HEUR_DESC "heuristic trying to solve the problem without objective"

#define	HEUR_DISPCHAR 'Z'

#define	HEUR_PRIORITY 100

#define	HEUR_FREQ -1

#define	HEUR_FREQOFS 0

#define	HEUR_MAXDEPTH 0

#define	HEUR_TIMING SCIP_HEURTIMING_BEFORENODE \| SCIP_HEURTIMING_BEFOREPRESOL

#define	HEUR_USESSUBSCIP TRUE

#define	EVENTHDLR_NAME "Zeroobj"

#define	EVENTHDLR_DESC "LP event handler for " HEUR_NAME " heuristic"

#define	DEFAULT_MAXNODES 1000LL /* maximum number of nodes to regard in the subproblem */

#define	DEFAULT_MINIMPROVE 0.01 /* factor by which zeroobj should at least improve the incumbent */

#define	DEFAULT_MINNODES 100LL /* minimum number of nodes to regard in the subproblem */

#define	DEFAULT_MAXLPITERS 5000LL /* maximum number of LP iterations to be performed in the subproblem */

#define	DEFAULT_NODESOFS 100LL /* number of nodes added to the contingent of the total nodes */

#define	DEFAULT_NODESQUOT 0.1 /* subproblem nodes in relation to nodes of the original problem */

#define	DEFAULT_ADDALLSOLS FALSE /* should all subproblem solutions be added to the original SCIP? */

#define	DEFAULT_ONLYWITHOUTSOL TRUE

#define	DEFAULT_USEUCT FALSE /* should uct node selection be used at the beginning of the search? */

Functions
static SCIP_RETCODE	createNewSol (SCIP scip, SCIP subscip, SCIP_VAR *subvars, SCIP_HEUR heur, SCIP_SOL subsol, SCIP_Bool success)

static	SCIP_DECL_EVENTEXEC (eventExecZeroobj)

static	SCIP_DECL_HEURCOPY (heurCopyZeroobj)

static	SCIP_DECL_HEURFREE (heurFreeZeroobj)

static	SCIP_DECL_HEURINIT (heurInitZeroobj)

static	SCIP_DECL_HEUREXEC (heurExecZeroobj)

static SCIP_RETCODE	setupAndSolveSubscip (SCIP scip, SCIP subscip, SCIP_HEUR heur, SCIP_RESULT result, SCIP_Real minimprove, SCIP_Longint nnodes)

SCIP_RETCODE	SCIPapplyZeroobj (SCIP scip, SCIP_HEUR heur, SCIP_RESULT *result, SCIP_Real minimprove, SCIP_Longint nnodes)

SCIP_RETCODE	SCIPincludeHeurZeroobj (SCIP *scip)

Macro Definition Documentation

◆ HEUR_NAME

#define HEUR_NAME "zeroobj"

Definition at line 29 of file heur_zeroobj.c.

Referenced by SCIP_DECL_HEURCOPY(), SCIPincludeHeurZeroobj(), and setupAndSolveSubscip().

◆ HEUR_DESC

#define HEUR_DESC "heuristic trying to solve the problem without objective"

Definition at line 30 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ HEUR_DISPCHAR

#define HEUR_DISPCHAR 'Z'

Definition at line 31 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ HEUR_PRIORITY

#define HEUR_PRIORITY 100

Definition at line 32 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ HEUR_FREQ

#define HEUR_FREQ -1

Definition at line 33 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ HEUR_FREQOFS

#define HEUR_FREQOFS 0

Definition at line 34 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ HEUR_MAXDEPTH

#define HEUR_MAXDEPTH 0

Definition at line 35 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ HEUR_TIMING

#define HEUR_TIMING SCIP_HEURTIMING_BEFORENODE | SCIP_HEURTIMING_BEFOREPRESOL

Definition at line 36 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ HEUR_USESSUBSCIP

#define HEUR_USESSUBSCIP TRUE

does the heuristic use a secondary SCIP instance?

Definition at line 37 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ EVENTHDLR_NAME

#define EVENTHDLR_NAME "Zeroobj"

Definition at line 40 of file heur_zeroobj.c.

Referenced by SCIP_DECL_EVENTEXEC(), and setupAndSolveSubscip().

◆ EVENTHDLR_DESC

#define EVENTHDLR_DESC "LP event handler for " HEUR_NAME " heuristic"

Definition at line 41 of file heur_zeroobj.c.

Referenced by setupAndSolveSubscip().

◆ DEFAULT_MAXNODES

#define DEFAULT_MAXNODES 1000LL /* maximum number of nodes to regard in the subproblem */

Definition at line 44 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_MINIMPROVE

#define DEFAULT_MINIMPROVE 0.01 /* factor by which zeroobj should at least improve the incumbent */

Definition at line 45 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_MINNODES

#define DEFAULT_MINNODES 100LL /* minimum number of nodes to regard in the subproblem */

Definition at line 46 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_MAXLPITERS

#define DEFAULT_MAXLPITERS 5000LL /* maximum number of LP iterations to be performed in the subproblem */

Definition at line 47 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_NODESOFS

#define DEFAULT_NODESOFS 100LL /* number of nodes added to the contingent of the total nodes */

Definition at line 48 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_NODESQUOT

#define DEFAULT_NODESQUOT 0.1 /* subproblem nodes in relation to nodes of the original problem */

Definition at line 49 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_ADDALLSOLS

#define DEFAULT_ADDALLSOLS FALSE /* should all subproblem solutions be added to the original SCIP? */

Definition at line 50 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_ONLYWITHOUTSOL

#define DEFAULT_ONLYWITHOUTSOL TRUE

should heuristic only be executed if no primal solution was found, yet?

Definition at line 51 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

◆ DEFAULT_USEUCT

#define DEFAULT_USEUCT FALSE /* should uct node selection be used at the beginning of the search? */

Definition at line 52 of file heur_zeroobj.c.

Referenced by SCIPincludeHeurZeroobj().

Function Documentation

◆ createNewSol()

static SCIP_RETCODE createNewSol	(	SCIP *	scip,
		SCIP *	subscip,
		SCIP_VAR **	subvars,
		SCIP_HEUR *	heur,
		SCIP_SOL *	subsol,
		SCIP_Bool *	success
	)

static

creates a new solution for the original problem by copying the solution of the subproblem

Parameters

scip	original SCIP data structure
subscip	SCIP structure of the subproblem
subvars	the variables of the subproblem
heur	zeroobj heuristic structure
subsol	solution of the subproblem
success	used to store whether new solution was found or not

Definition at line 80 of file heur_zeroobj.c.

References FALSE, SCIP_CALL, SCIP_OKAY, SCIP_Real, SCIPallocBufferArray, SCIPcreateSol(), SCIPfreeBufferArray, SCIPgetNOrigVars(), SCIPgetSolVals(), SCIPgetVarsData(), SCIPsetSolVals(), SCIPtrySolFree(), and TRUE.

Referenced by setupAndSolveSubscip().

◆ SCIP_DECL_EVENTEXEC()

static SCIP_DECL_EVENTEXEC ( eventExecZeroobj )

static

Definition at line 131 of file heur_zeroobj.c.

References EVENTHDLR_NAME, SCIP_CALL, SCIP_EVENTTYPE_NODESOLVED, SCIP_LPSOLSTAT_ITERLIMIT, SCIP_OKAY, SCIPeventGetType(), SCIPeventhdlrGetName(), SCIPgetLPSolstat(), SCIPgetNLPIterations(), and SCIPinterruptSolve().

◆ SCIP_DECL_HEURCOPY()

static SCIP_DECL_HEURCOPY ( heurCopyZeroobj )

static

copy method for primal heuristic plugins (called when SCIP copies plugins)

Definition at line 156 of file heur_zeroobj.c.

References HEUR_NAME, SCIP_CALL, SCIP_OKAY, SCIPheurGetName(), and SCIPincludeHeurZeroobj().

◆ SCIP_DECL_HEURFREE()

static SCIP_DECL_HEURFREE ( heurFreeZeroobj )

static

destructor of primal heuristic to free user data (called when SCIP is exiting)

Definition at line 170 of file heur_zeroobj.c.

References SCIP_OKAY, SCIPfreeBlockMemory, SCIPheurGetData(), and SCIPheurSetData().

◆ SCIP_DECL_HEURINIT()

static SCIP_DECL_HEURINIT ( heurInitZeroobj )

static

initialization method of primal heuristic (called after problem was transformed)

Definition at line 191 of file heur_zeroobj.c.

References SCIP_OKAY, and SCIPheurGetData().

◆ SCIP_DECL_HEUREXEC()

static SCIP_DECL_HEUREXEC ( heurExecZeroobj )

static

execution method of primal heuristic

Definition at line 211 of file heur_zeroobj.c.

References nnodes, SCIP_CALL, SCIP_Longint, SCIP_OKAY, SCIPapplyZeroobj(), SCIPdebugMsg, SCIPgetNNodes(), SCIPgetNObjVars(), SCIPheurGetData(), SCIPheurGetNBestSolsFound(), SCIPheurGetNCalls(), and SCIPisStopped().

◆ setupAndSolveSubscip()

static SCIP_RETCODE setupAndSolveSubscip	(	SCIP *	scip,
		SCIP *	subscip,
		SCIP_HEUR *	heur,
		SCIP_RESULT *	result,
		SCIP_Real	minimprove,
		SCIP_Longint	nnodes
	)

static

setup and solve subscip

Parameters

scip	SCIP data structure
subscip	SCIP data structure
heur	heuristic data structure
result	result data structure
minimprove	factor by which zeroobj should at least improve the incumbent
nnodes	node limit for the subproblem

Definition at line 261 of file heur_zeroobj.c.

References createNewSol(), EVENTHDLR_DESC, EVENTHDLR_NAME, FALSE, HEUR_NAME, MAX, SCIP_Bool, SCIP_CALL, SCIP_CALL_ABORT, SCIP_EVENTTYPE_NODESOLVED, SCIP_FOUNDSOL, SCIP_OKAY, SCIP_PARAMSETTING_FAST, SCIP_PARAMSETTING_OFF, SCIP_PLUGINNOTFOUND, SCIP_Real, SCIPaddCoefLinear(), SCIPaddCons(), SCIPallocBufferArray, SCIPblkmem(), SCIPcatchEvent(), SCIPchgVarLbGlobal(), SCIPchgVarObj(), SCIPchgVarUbGlobal(), SCIPcopy(), SCIPcopyLimits(), SCIPcreateConsLinear(), SCIPdebugMsg, SCIPdropEvent(), SCIPerrorMessage, SCIPfeastol(), SCIPfindBranchrule(), SCIPfindConshdlr(), SCIPfindNodesel(), SCIPfreeBufferArray, SCIPgetLowerbound(), SCIPgetNObjVars(), SCIPgetNSols(), SCIPgetSols(), SCIPgetUpperbound(), SCIPgetVarsData(), SCIPhashmapCreate(), SCIPhashmapFree(), SCIPhashmapGetImage(), SCIPheurGetData(), SCIPincludeEventhdlrBasic(), SCIPinfinity(), SCIPisFeasZero(), SCIPisInfinity(), SCIPisParamFixed(), SCIPprintStatistics(), SCIPreleaseCons(), SCIPsetBoolParam(), SCIPsetIntParam(), SCIPsetLongintParam(), SCIPsetPresolving(), SCIPsetSeparating(), SCIPsetSubscipsOff(), SCIPsolve(), SCIPsumepsilon(), SCIPtransformProb(), SCIPvarGetLbGlobal(), SCIPvarGetObj(), SCIPvarGetUbGlobal(), and TRUE.

Referenced by SCIPapplyZeroobj().

SCIP

Detailed Description

Macros

Functions

Macro Definition Documentation

◆ HEUR_NAME

◆ HEUR_DESC

◆ HEUR_DISPCHAR

◆ HEUR_PRIORITY

◆ HEUR_FREQ

◆ HEUR_FREQOFS

◆ HEUR_MAXDEPTH

◆ HEUR_TIMING

◆ HEUR_USESSUBSCIP

◆ EVENTHDLR_NAME

◆ EVENTHDLR_DESC

◆ DEFAULT_MAXNODES

◆ DEFAULT_MINIMPROVE

◆ DEFAULT_MINNODES

◆ DEFAULT_MAXLPITERS

◆ DEFAULT_NODESOFS

◆ DEFAULT_NODESQUOT

◆ DEFAULT_ADDALLSOLS

◆ DEFAULT_ONLYWITHOUTSOL

◆ DEFAULT_USEUCT

Function Documentation

◆ createNewSol()

◆ SCIP_DECL_EVENTEXEC()

◆ SCIP_DECL_HEURCOPY()

◆ SCIP_DECL_HEURFREE()

◆ SCIP_DECL_HEURINIT()

◆ SCIP_DECL_HEUREXEC()

◆ setupAndSolveSubscip()