Detailed Description

methods to initiate and conduct LP diving

Functions
SCIP_RETCODE	SCIPstartDive (SCIP *scip)

SCIP_RETCODE	SCIPendDive (SCIP *scip)

SCIP_RETCODE	SCIPchgCutoffboundDive (SCIP *scip, SCIP_Real newcutoffbound)

SCIP_RETCODE	SCIPchgVarObjDive (SCIP scip, SCIP_VAR var, SCIP_Real newobj)

SCIP_RETCODE	SCIPchgVarLbDive (SCIP scip, SCIP_VAR var, SCIP_Real newbound)

SCIP_RETCODE	SCIPchgVarUbDive (SCIP scip, SCIP_VAR var, SCIP_Real newbound)

SCIP_RETCODE	SCIPaddRowDive (SCIP scip, SCIP_ROW row)

SCIP_RETCODE	SCIPchgRowLhsDive (SCIP scip, SCIP_ROW row, SCIP_Real newlhs)

SCIP_RETCODE	SCIPchgRowRhsDive (SCIP scip, SCIP_ROW row, SCIP_Real newrhs)

SCIP_Real	SCIPgetVarObjDive (SCIP scip, SCIP_VAR var)

SCIP_Real	SCIPgetVarLbDive (SCIP scip, SCIP_VAR var)

SCIP_Real	SCIPgetVarUbDive (SCIP scip, SCIP_VAR var)

SCIP_RETCODE	SCIPsolveDiveLP (SCIP scip, int itlim, SCIP_Bool lperror, SCIP_Bool *cutoff)

SCIP_Longint	SCIPgetLastDivenode (SCIP *scip)

SCIP_Bool	SCIPinDive (SCIP *scip)

SCIP_RETCODE	SCIPgetLPDualDegeneracy (SCIP scip, SCIP_Real degeneracy, SCIP_Real *varconsratio)

Function Documentation

◆ SCIPstartDive()

SCIP_RETCODE SCIPstartDive ( SCIP * scip )

initiates LP diving, making methods SCIPchgVarObjDive(), SCIPchgVarLbDive(), and SCIPchgVarUbDive() available

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Note: diving is allowed even if the current LP is not flushed, not solved, or not solved to optimality; be aware that solving the (first) diving LP may take longer than expect and that the latter two cases could stem from numerical troubles during the last LP solve; because of this, most users will want to call this method only if SCIPgetLPSolstat(scip) == SCIP_LPSOLSTAT_OPTIMAL

Parameters

scip	SCIP data structure

Definition at line 2206 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_NODETYPE_FOCUSNODE, SCIP_OKAY, SCIPcheckStage, SCIPerrorMessage, SCIPgetCurrentNode(), SCIPisRelaxSolValid(), SCIPlpDiving(), SCIPlpStartDive(), SCIPnodeGetType(), SCIPtreeHasCurrentNodeLP(), SCIPtreeIsFocusNodeLPConstructed(), SCIPtreeProbing(), SCIPtreeStoreRelaxSol(), and TRUE.

Referenced by createLPWithSoftCuts(), SCIP_DECL_BRANCHEXECLP(), SCIP_DECL_HEUREXEC(), SCIPstartExactDive(), and solveLp().

◆ SCIPendDive()

SCIP_RETCODE SCIPendDive ( SCIP * scip )

quits LP diving and resets bounds and objective values of columns to the current node's values

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure

Definition at line 2255 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage, SCIPerrorMessage, SCIPisExact(), SCIPlpDiving(), SCIPlpEndDive(), SCIPlpExactDiving(), SCIPlpIsRelax(), SCIPlpIsSolved(), SCIPlpSetCutoffbound(), SCIPnodeUpdateLowerboundLP(), SCIPtreeCutoff(), SCIPtreeIsFocusNodeLPConstructed(), SCIPtreeRestoreRelaxSol(), and TRUE.

Referenced by deleteLPWithSoftCuts(), SCIP_DECL_BRANCHEXECLP(), SCIP_DECL_HEUREXEC(), SCIPendExactDive(), and solveLp().

◆ SCIPchgCutoffboundDive()

SCIP_RETCODE SCIPchgCutoffboundDive	(	SCIP *	scip,
		SCIP_Real	newcutoffbound
	)

changes cutoffbound in current dive

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
newcutoffbound	new cutoffbound

Definition at line 2313 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPlpSetCutoffbound(), and TRUE.

◆ SCIPchgVarObjDive()

SCIP_RETCODE SCIPchgVarObjDive	(	SCIP *	scip,
		SCIP_VAR *	var,
		SCIP_Real	newobj
	)

changes variable's objective value in current dive

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
var	variable to change the objective value for
newobj	new objective value

Definition at line 2343 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPlpMarkDivingObjChanged(), SCIPlpSetCutoffbound(), SCIPsetInfinity(), SCIPvarChgObjDive(), and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP(), SCIP_DECL_HEUREXEC(), updateObjectiveVector(), and updateVariableRounding().

◆ SCIPchgVarLbDive()

SCIP_RETCODE SCIPchgVarLbDive	(	SCIP *	scip,
		SCIP_VAR *	var,
		SCIP_Real	newbound
	)

changes variable's lower bound in current dive

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
var	variable to change the bound for
newbound	new value for bound

Definition at line 2384 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPvarChgLbDive(), and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP(), SCIP_DECL_CONSCHECK(), SCIP_DECL_HEUREXEC(), and solveLp().

◆ SCIPchgVarUbDive()

SCIP_RETCODE SCIPchgVarUbDive	(	SCIP *	scip,
		SCIP_VAR *	var,
		SCIP_Real	newbound
	)

changes variable's upper bound in current dive

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
var	variable to change the bound for
newbound	new value for bound

Definition at line 2416 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPvarChgUbDive(), and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP(), SCIP_DECL_CONSCHECK(), SCIP_DECL_HEUREXEC(), and solveLp().

◆ SCIPaddRowDive()

SCIP_RETCODE SCIPaddRowDive	(	SCIP *	scip,
		SCIP_ROW *	row
	)

adds a row to the LP in current dive

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
row	row to be added

Definition at line 2448 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage, SCIPerrorMessage, SCIPlpAddRow(), SCIPlpDiving(), SCIPnodeGetDepth(), SCIPtreeGetCurrentNode(), and TRUE.

◆ SCIPchgRowLhsDive()

SCIP_RETCODE SCIPchgRowLhsDive	(	SCIP *	scip,
		SCIP_ROW *	row,
		SCIP_Real	newlhs
	)

changes row lhs in current dive, change will be undone after diving ends, for permanent changes use SCIPchgRowLhs()

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
row	row to change the lhs for
newlhs	new value for lhs

Definition at line 2487 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIP_SIDETYPE_LEFT, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPlpRecordOldRowSideDive(), SCIProwChgLhs(), and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP().

◆ SCIPchgRowRhsDive()

SCIP_RETCODE SCIPchgRowRhsDive	(	SCIP *	scip,
		SCIP_ROW *	row,
		SCIP_Real	newrhs
	)

changes row rhs in current dive, change will be undone after diving ends, for permanent changes use SCIPchgRowRhs()

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
row	row to change the lhs for
newrhs	new value for rhs

Definition at line 2520 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIP_SIDETYPE_RIGHT, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPlpRecordOldRowSideDive(), SCIProwChgRhs(), and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP().

◆ SCIPgetVarObjDive()

SCIP_Real SCIPgetVarObjDive	(	SCIP *	scip,
		SCIP_VAR *	var
	)

gets variable's objective value in current dive

Returns: the variable's objective value in current dive.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
var	variable to get the bound for

Definition at line 2552 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL_ABORT, SCIP_INVALID, SCIPABORT, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPvarGetObjLP(), and TRUE.

Referenced by SCIP_DECL_HEUREXEC(), and updateObjectiveVector().

◆ SCIPgetVarLbDive()

SCIP_Real SCIPgetVarLbDive	(	SCIP *	scip,
		SCIP_VAR *	var
	)

gets variable's lower bound in current dive

Returns: the variable's lower bound in current dive.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
var	variable to get the bound for

Definition at line 2581 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL_ABORT, SCIP_INVALID, SCIPABORT, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPvarGetLbLP(), and TRUE.

Referenced by SCIP_DECL_HEUREXEC().

◆ SCIPgetVarUbDive()

SCIP_Real SCIPgetVarUbDive	(	SCIP *	scip,
		SCIP_VAR *	var
	)

gets variable's upper bound in current dive

Returns: the variable's upper bound in current dive.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure
var	variable to get the bound for

Definition at line 2610 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL_ABORT, SCIP_INVALID, SCIPABORT, SCIPcheckStage, SCIPerrorMessage, SCIPlpDiving(), SCIPvarGetUbLP(), and TRUE.

Referenced by SCIP_DECL_HEUREXEC().

◆ SCIPsolveDiveLP()

SCIP_RETCODE SCIPsolveDiveLP	(	SCIP *	scip,
		int	itlim,
		SCIP_Bool *	lperror,
		SCIP_Bool *	cutoff
	)

solves the LP of the current dive; no separation or pricing is applied

Returns: SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See SCIP_RETCODE for a complete list of error codes.

Precondition

This method can be called if scip is in one of the following stages:

SCIP_STAGE_SOLVING

See SCIP_STAGE for a complete list of all possible solving stages.

Note: be aware that the LP solve may take longer than expected if SCIPgetLPSolstat(scip) != SCIP_LPSOLSTAT_OPTIMAL, compare the explanation of SCIPstartDive()

Parameters

scip	SCIP data structure
itlim	maximal number of LP iterations to perform, or -1 for no limit
lperror	pointer to store whether an unresolved LP error occurred
cutoff	pointer to store whether the diving LP was infeasible or the objective limit was reached (or NULL, if not needed)

Definition at line 2643 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_Longint, SCIP_LPSOLSTAT_INFEASIBLE, SCIP_LPSOLSTAT_OBJLIMIT, SCIP_LPSOLSTAT_OPTIMAL, SCIP_OKAY, SCIPcheckStage, SCIPconflictAnalyzeLP(), SCIPerrorMessage, SCIPgetCutoffbound(), SCIPgetLPObjval(), SCIPisGE(), SCIPlpDiving(), SCIPlpDivingObjChanged(), SCIPlpDivingRowsChanged(), SCIPlpGetSolstat(), SCIPlpSolveAndEval(), SCIPprobAllColsInLP(), and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP(), SCIP_DECL_HEUREXEC(), solveLagromoryLP(), and solveLp().

◆ SCIPgetLastDivenode()

SCIP_Longint SCIPgetLastDivenode ( SCIP * scip )

returns the number of the node in the current branch and bound run, where the last LP was solved in diving or probing mode

Returns: the number of the node in the current branch and bound run, where the last LP was solved in diving or probing mode.

Precondition

This method can be called if scip is in one of the following stages:

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure

Definition at line 2710 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL_ABORT, SCIPcheckStage, and TRUE.

Referenced by SCIP_DECL_HEUREXEC(), and SCIPperformGenericDivingAlgorithm().

◆ SCIPinDive()

SCIP_Bool SCIPinDive ( SCIP * scip )

returns whether we are in diving mode

Returns: whether we are in diving mode.

Precondition

This method can be called if scip is in one of the following stages:

See SCIP_STAGE for a complete list of all possible solving stages.

Parameters

scip	SCIP data structure

Definition at line 2740 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL_ABORT, SCIPcheckStage, SCIPlpDiving(), and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP(), SCIP_DECL_CONSCHECK(), SCIP_DECL_HEUREXEC(), SCIP_DECL_PROPEXEC(), SCIP_DECL_RELAXEXEC(), SCIPtightenVarLb(), SCIPtightenVarLbExact(), SCIPtightenVarUb(), SCIPtightenVarUbExact(), solveLp(), and updateSubproblemLowerbound().

◆ SCIPgetLPDualDegeneracy()

SCIP_RETCODE SCIPgetLPDualDegeneracy	(	SCIP *	scip,
		SCIP_Real *	degeneracy,
		SCIP_Real *	varconsratio
	)

computes two measures for dual degeneracy (dual degeneracy rate and variable-constraint ratio) based on the changes applied when reducing the problem to the optimal face

returns the dual degeneracy rate, i.e., the share of nonbasic variables with reduced cost 0 and the variable-constraint ratio, i.e., the number of unfixed variables in relation to the basis size

Parameters

scip	SCIP data structure
degeneracy	pointer to store the dual degeneracy rate
varconsratio	pointer to store the variable-constraint ratio

Definition at line 2757 of file scip_lp.c.

References FALSE, NULL, SCIP_CALL, SCIP_OKAY, SCIPcheckStage, SCIPlpGetDualDegeneracy(), and TRUE.

Referenced by checkExec(), execRelpscost(), and SCIP_DECL_SEPAEXECLP().

SCIP

Detailed Description

Functions

Function Documentation

◆ SCIPstartDive()

◆ SCIPendDive()

◆ SCIPchgCutoffboundDive()

◆ SCIPchgVarObjDive()

◆ SCIPchgVarLbDive()

◆ SCIPchgVarUbDive()

◆ SCIPaddRowDive()

◆ SCIPchgRowLhsDive()

◆ SCIPchgRowRhsDive()

◆ SCIPgetVarObjDive()

◆ SCIPgetVarLbDive()

◆ SCIPgetVarUbDive()

◆ SCIPsolveDiveLP()

◆ SCIPgetLastDivenode()

◆ SCIPinDive()

◆ SCIPgetLPDualDegeneracy()