Detailed Description

constraint handler for SOS type 1 constraints

Author: Tobias Fischer; Marc Pfetsch

A specially ordered set of type 1 (SOS1) is a sequence of variables such that at most one variable is nonzero. The special case of two variables arises, for instance, from equilibrium or complementary conditions like $x \cdot y = 0$ . Note that it is in principle allowed that a variable appears twice, but it then can be fixed to 0.

Definition in file cons_sos1.h.

#include "scip/scip.h"

Go to the source code of this file.

Functions
SCIP_RETCODE	SCIPincludeConshdlrSOS1 (SCIP *scip)

SCIP_RETCODE	SCIPcreateConsSOS1 (SCIP scip, SCIP_CONS cons, const char name, int nvars, SCIP_VAR *vars, SCIP_Real weights, SCIP_Bool initial, SCIP_Bool separate, SCIP_Bool enforce, SCIP_Bool check, SCIP_Bool propagate, SCIP_Bool local, SCIP_Bool dynamic, SCIP_Bool removable, SCIP_Bool stickingatnode)

SCIP_RETCODE	SCIPcreateConsBasicSOS1 (SCIP scip, SCIP_CONS cons, const char name, int nvars, SCIP_VAR *vars, SCIP_Real weights)

SCIP_RETCODE	SCIPaddVarSOS1 (SCIP scip, SCIP_CONS cons, SCIP_VAR *var, SCIP_Real weight)

SCIP_RETCODE	SCIPappendVarSOS1 (SCIP scip, SCIP_CONS cons, SCIP_VAR *var)

int	SCIPgetNVarsSOS1 (SCIP scip, SCIP_CONS cons)

SCIP_VAR **	SCIPgetVarsSOS1 (SCIP scip, SCIP_CONS cons)

SCIP_Real *	SCIPgetWeightsSOS1 (SCIP scip, SCIP_CONS cons)

SCIP_DIGRAPH *	SCIPgetConflictgraphSOS1 (SCIP_CONSHDLR *conshdlr)

int	SCIPgetNSOS1Vars (SCIP_CONSHDLR *conshdlr)

SCIP_Bool	SCIPvarIsSOS1 (SCIP_CONSHDLR conshdlr, SCIP_VAR var)

int	SCIPvarGetNodeSOS1 (SCIP_CONSHDLR conshdlr, SCIP_VAR var)

SCIP_VAR *	SCIPnodeGetVarSOS1 (SCIP_DIGRAPH *conflictgraph, int node)

SCIP_RETCODE	SCIPmakeSOS1sFeasible (SCIP scip, SCIP_CONSHDLR conshdlr, SCIP_SOL sol, SCIP_Bool changed, SCIP_Bool *success)

Function Documentation

SCIP_RETCODE SCIPincludeConshdlrSOS1 ( SCIP * scip )

creates the handler for SOS1 constraints and includes it in SCIP

Parameters

scip	SCIP data structure

SCIP_RETCODE SCIPcreateConsSOS1	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		int	nvars,
		SCIP_VAR **	vars,
		SCIP_Real *	weights,
		SCIP_Bool	initial,
		SCIP_Bool	separate,
		SCIP_Bool	enforce,
		SCIP_Bool	check,
		SCIP_Bool	propagate,
		SCIP_Bool	local,
		SCIP_Bool	dynamic,
		SCIP_Bool	removable,
		SCIP_Bool	stickingatnode
	)

creates and captures an SOS1 constraint

We set the constraint to not be modifable. If the weights are non NULL, the variables are ordered according to these weights (in ascending order).

Note: The constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons().

Parameters

scip	SCIP data structure
cons	pointer to hold the created constraint
name	name of constraint
nvars	number of variables in the constraint
vars	array with variables of constraint entries
weights	weights determining the variable order, or NULL if natural order should be used
initial	should the LP relaxation of constraint be in the initial LP? Usually set to TRUE. Set to FALSE for 'lazy constraints'.
separate	should the constraint be separated during LP processing? Usually set to TRUE.
enforce	should the constraint be enforced during node processing? TRUE for model constraints, FALSE for additional, redundant constraints.
check	should the constraint be checked for feasibility? TRUE for model constraints, FALSE for additional, redundant constraints.
propagate	should the constraint be propagated during node processing? Usually set to TRUE.
local	is constraint only valid locally? Usually set to FALSE. Has to be set to TRUE, e.g., for branching constraints.
dynamic	is constraint subject to aging? Usually set to FALSE. Set to TRUE for own cuts which are separated as constraints.
removable	should the relaxation be removed from the LP due to aging or cleanup? Usually set to FALSE. Set to TRUE for 'lazy constraints' and 'user cuts'.
stickingatnode	should the constraint always be kept at the node where it was added, even if it may be moved to a more global node? Usually set to FALSE. Set to TRUE to for constraints that represent node data.

SCIP_RETCODE SCIPcreateConsBasicSOS1	(	SCIP *	scip,
		SCIP_CONS **	cons,
		const char *	name,
		int	nvars,
		SCIP_VAR **	vars,
		SCIP_Real *	weights
	)

creates and captures an SOS1 constraint in its most basic variant, i. e., with all constraint flags set to their default values, which can be set afterwards using SCIPsetConsFLAGNAME() in scip.h

See also: SCIPcreateConsSOS1() for the default constraint flag configuration

Warning: Do NOT set the constraint to be modifiable manually, because this might lead to wrong results as the variable array will not be resorted

Note: the constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons()

Parameters

scip	SCIP data structure
cons	pointer to hold the created constraint
name	name of constraint
nvars	number of variables in the constraint
vars	array with variables of constraint entries
weights	weights determining the variable order, or NULL if natural order should be used

SCIP_RETCODE SCIPaddVarSOS1	(	SCIP *	scip,
		SCIP_CONS *	cons,
		SCIP_VAR *	var,
		SCIP_Real	weight
	)

adds variable to SOS1 constraint, the position is determined by the given weight

Parameters

scip	SCIP data structure
cons	constraint
var	variable to add to the constraint
weight	weight determining position of variable

SCIP_RETCODE SCIPappendVarSOS1	(	SCIP *	scip,
		SCIP_CONS *	cons,
		SCIP_VAR *	var
	)

appends variable to SOS1 constraint

Parameters

scip	SCIP data structure
cons	constraint
var	variable to add to the constraint

int SCIPgetNVarsSOS1	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets number of variables in SOS1 constraint

Parameters

scip	SCIP data structure
cons	constraint

SCIP_VAR** SCIPgetVarsSOS1	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets array of variables in SOS1 constraint

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_Real* SCIPgetWeightsSOS1	(	SCIP *	scip,
		SCIP_CONS *	cons
	)

gets array of weights in SOS1 constraint (or NULL if not existent)

Parameters

scip	SCIP data structure
cons	constraint data

SCIP_DIGRAPH* SCIPgetConflictgraphSOS1 ( SCIP_CONSHDLR * conshdlr )

gets conflict graph of SOS1 constraints (or NULL if not existent)

Note: The conflict graph is globally valid; local changes are not taken into account.

Parameters

conshdlr SOS1 constraint handler

int SCIPgetNSOS1Vars ( SCIP_CONSHDLR * conshdlr )

gets number of problem variables that are part of the SOS1 conflict graph

Parameters

conshdlr SOS1 constraint handler

SCIP_Bool SCIPvarIsSOS1	(	SCIP_CONSHDLR *	conshdlr,
		SCIP_VAR *	var
	)

returns whether variable is part of the SOS1 conflict graph

Parameters

conshdlr	SOS1 constraint handler
var	variable

int SCIPvarGetNodeSOS1	(	SCIP_CONSHDLR *	conshdlr,
		SCIP_VAR *	var
	)

returns node of variable in the conflict graph or -1 if variable is not part of the SOS1 conflict graph

Parameters

conshdlr	SOS1 constraint handler
var	variable

SCIP_VAR* SCIPnodeGetVarSOS1	(	SCIP_DIGRAPH *	conflictgraph,
		int	node
	)

returns variable that belongs to a given node from the conflict graph

Parameters

conflictgraph	conflict graph
node	node from the conflict graph

SCIP_RETCODE SCIPmakeSOS1sFeasible	(	SCIP *	scip,
		SCIP_CONSHDLR *	conshdlr,
		SCIP_SOL *	sol,
		SCIP_Bool *	changed,
		SCIP_Bool *	success
	)

based on solution values of the variables, fixes variables to zero to turn all SOS1 constraints feasible

Parameters

scip	SCIP pointer
conshdlr	SOS1 constraint handler
sol	solution
changed	pointer to store whether the solution has been changed
success	pointer to store whether SOS1 constraints have been turned feasible and solution was good enough

SCIP

Detailed Description

Functions

Function Documentation