Detailed Description

methods to initiate and conduct LP diving

Functions
SCIP_EXPORT SCIP_RETCODE	SCIPstartDive (SCIP *scip)

SCIP_EXPORT SCIP_RETCODE	SCIPendDive (SCIP *scip)

SCIP_EXPORT SCIP_RETCODE	SCIPchgCutoffboundDive (SCIP *scip, SCIP_Real newcutoffbound)

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

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

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

SCIP_EXPORT SCIP_RETCODE	SCIPaddRowDive (SCIP scip, SCIP_ROW row)

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

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

SCIP_EXPORT SCIP_Real	SCIPgetVarObjDive (SCIP scip, SCIP_VAR var)

SCIP_EXPORT SCIP_Real	SCIPgetVarLbDive (SCIP scip, SCIP_VAR var)

SCIP_EXPORT SCIP_Real	SCIPgetVarUbDive (SCIP scip, SCIP_VAR var)

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

SCIP_EXPORT SCIP_Longint	SCIPgetLastDivenode (SCIP *scip)

SCIP_EXPORT SCIP_Bool	SCIPinDive (SCIP *scip)

SCIP_EXPORT SCIP_RETCODE	SCIPgetLPDegeneracy (SCIP scip, SCIP_Real degeneracy, SCIP_Real *varconsratio)

Function Documentation

◆ SCIPstartDive()

SCIP_EXPORT 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 2182 of file scip_lp.c.

References FALSE, Scip::lp, Scip::mem, NULL, SCIP_Mem::probmem, Scip::relaxation, SCIP_CALL, SCIP_INVALIDCALL, SCIP_NODETYPE_FOCUSNODE, SCIP_OKAY, SCIPcheckStage(), SCIPerrorMessage, SCIPgetCurrentNode(), SCIPisRelaxSolValid(), SCIPlpDiving(), SCIPlpStartDive(), SCIPnodeGetType(), SCIPtreeHasCurrentNodeLP(), SCIPtreeIsFocusNodeLPConstructed(), SCIPtreeProbing(), SCIPtreeStoreRelaxSol(), Scip::set, Scip::stat, Scip::transprob, Scip::tree, and TRUE.

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

◆ SCIPendDive()

SCIP_EXPORT 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 2231 of file scip_lp.c.

References SCIP_Primal::cutoffbound, SCIP_Lp::cutoffbound, SCIP_Tree::cutoffdelayed, Scip::eventfilter, Scip::eventqueue, FALSE, SCIP_Tree::focusnode, Scip::lp, Scip::mem, Scip::messagehdlr, NULL, SCIP_Prob::nvars, Scip::origprob, Scip::primal, SCIP_Tree::probdiverelaxstored, SCIP_Mem::probmem, Scip::relaxation, Scip::reopt, SCIP_Lp::resolvelperror, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage(), SCIPerrorMessage, SCIPlpDiving(), SCIPlpEndDive(), SCIPlpIsRelax(), SCIPlpIsSolved(), SCIPlpSetCutoffbound(), SCIPnodeUpdateLowerboundLP(), SCIPtreeCutoff(), SCIPtreeIsFocusNodeLPConstructed(), SCIPtreeRestoreRelaxSol(), Scip::set, Scip::stat, Scip::transprob, Scip::tree, TRUE, and SCIP_Prob::vars.

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

◆ SCIPchgCutoffboundDive()

SCIP_EXPORT 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 2288 of file scip_lp.c.

References FALSE, Scip::lp, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage(), SCIPerrorMessage, SCIPlpDiving(), SCIPlpSetCutoffbound(), Scip::set, Scip::transprob, and TRUE.

◆ SCIPchgVarObjDive()

SCIP_EXPORT 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 2318 of file scip_lp.c.

References FALSE, Scip::lp, NULL, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage(), SCIPerrorMessage, SCIPlpDiving(), SCIPlpMarkDivingObjChanged(), SCIPlpSetCutoffbound(), SCIPsetInfinity(), SCIPvarChgObjDive(), Scip::set, Scip::transprob, and TRUE.

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

◆ SCIPchgVarLbDive()

SCIP_EXPORT 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 2359 of file scip_lp.c.

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

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

◆ SCIPchgVarUbDive()

SCIP_EXPORT 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 2391 of file scip_lp.c.

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

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

◆ SCIPaddRowDive()

SCIP_EXPORT 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 2423 of file scip_lp.c.

References Scip::eventfilter, Scip::eventqueue, FALSE, Scip::lp, Scip::mem, NULL, SCIP_Mem::probmem, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIPcheckStage(), SCIPerrorMessage, SCIPlpAddRow(), SCIPlpDiving(), SCIPnodeGetDepth(), SCIPtreeGetCurrentNode(), Scip::set, Scip::tree, and TRUE.

◆ SCIPchgRowLhsDive()

SCIP_EXPORT 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 2462 of file scip_lp.c.

References Scip::eventqueue, FALSE, Scip::lp, Scip::mem, NULL, SCIP_Mem::probmem, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIP_SIDETYPE_LEFT, SCIPcheckStage(), SCIPerrorMessage, SCIPlpDiving(), SCIPlpRecordOldRowSideDive(), SCIProwChgLhs(), Scip::set, and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP().

◆ SCIPchgRowRhsDive()

SCIP_EXPORT 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 2495 of file scip_lp.c.

References Scip::eventqueue, FALSE, Scip::lp, Scip::mem, NULL, SCIP_Mem::probmem, SCIP_CALL, SCIP_INVALIDCALL, SCIP_OKAY, SCIP_SIDETYPE_RIGHT, SCIPcheckStage(), SCIPerrorMessage, SCIPlpDiving(), SCIPlpRecordOldRowSideDive(), SCIProwChgRhs(), Scip::set, and TRUE.

Referenced by SCIP_DECL_BRANCHEXECLP().

◆ SCIPgetVarObjDive()

SCIP_EXPORT 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 2527 of file scip_lp.c.

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

Referenced by SCIP_DECL_HEUREXEC().

◆ SCIPgetVarLbDive()

SCIP_EXPORT 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 2556 of file scip_lp.c.

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

Referenced by SCIP_DECL_HEUREXEC().

◆ SCIPgetVarUbDive()

SCIP_EXPORT 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 2585 of file scip_lp.c.

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

Referenced by SCIP_DECL_HEUREXEC().

◆ SCIPsolveDiveLP()

SCIP_EXPORT 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 2618 of file scip_lp.c.

References Scip::branchcand, Scip::cliquetable, Scip::conflict, Scip::conflictstore, Scip::eventfilter, Scip::eventqueue, FALSE, Scip::lp, Scip::mem, Scip::messagehdlr, SCIP_Set::misc_exactsolve, NULL, Scip::origprob, SCIP_Mem::probmem, Scip::reopt, 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(), Scip::set, Scip::stat, Scip::transprob, Scip::tree, and TRUE.

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

◆ SCIPgetLastDivenode()

SCIP_EXPORT 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 2685 of file scip_lp.c.

References FALSE, SCIP_Stat::lastdivenode, NULL, SCIP_CALL_ABORT, SCIPcheckStage(), Scip::stat, and TRUE.

Referenced by SCIP_DECL_HEUREXEC(), and SCIPperformGenericDivingAlgorithm().

◆ SCIPinDive()

SCIP_EXPORT 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 2715 of file scip_lp.c.

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

Referenced by SCIP_DECL_PROPEXEC(), SCIP_DECL_RELAXEXEC(), SCIPtightenVarLb(), SCIPtightenVarUb(), storeAllBilinearTerms(), and updateSubproblemLowerbound().

◆ SCIPgetLPDegeneracy()

SCIP_EXPORT SCIP_RETCODE SCIPgetLPDegeneracy	(	SCIP *	scip,
		SCIP_Real *	degeneracy,
		SCIP_Real *	varconsratio
	)

computes the changes to the problem when fixing to the optimal face

returns the degeneracy rate, i.e., the number 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 degeneracy share
varconsratio	pointer to store variable constraint ratio

Definition at line 2731 of file scip_lp.c.

References FALSE, Scip::lp, NULL, SCIP_CALL, SCIP_OKAY, SCIPcheckStage(), SCIPlpGetDegeneracy(), Scip::set, Scip::stat, and TRUE.

Referenced by execRelpscost().

SCIP

Detailed Description

Functions

Function Documentation

◆ SCIPstartDive()

◆ SCIPendDive()

◆ SCIPchgCutoffboundDive()

◆ SCIPchgVarObjDive()

◆ SCIPchgVarLbDive()

◆ SCIPchgVarUbDive()

◆ SCIPaddRowDive()

◆ SCIPchgRowLhsDive()

◆ SCIPchgRowRhsDive()

◆ SCIPgetVarObjDive()

◆ SCIPgetVarLbDive()

◆ SCIPgetVarUbDive()

◆ SCIPsolveDiveLP()

◆ SCIPgetLastDivenode()

◆ SCIPinDive()

◆ SCIPgetLPDegeneracy()