
constraint handler for (partitioning/packing) orbitope constraints w.r.t. the full symmetric group
 Author
 Timo Berthold

Marc Pfetsch
This constraint handler can be used to handle symmetries in certain 0/1programs. The principle structure is that some variables can be ordered in matrix form, such that permuting columns does not change the validity and objective function value of a solution. That is, the symmetry group of the program contains the full symmetric group obtained by permuting the columns of this matrix. The variables in each row have to be contained in set packing or partitioning constraints.
In more mathematical terms the structure has to be as follows: There are 0/1variables , , . The variables are coupled through set packing or partitioning constraints:
Permuting columns of does not change the validity and objective function value of any feasible solution.
Definition in file cons_orbitope.h.
Go to the source code of this file.

SCIP_RETCODE  SCIPincludeConshdlrOrbitope (SCIP *scip) 

SCIP_RETCODE  SCIPcreateConsOrbitope (SCIP *scip, SCIP_CONS **cons, const char *name, SCIP_VAR ***vars, SCIP_Bool ispart, int nspcons, int nblocks, SCIP_Bool resolveprop, SCIP_Bool initial, SCIP_Bool separate, SCIP_Bool enforce, SCIP_Bool check, SCIP_Bool propagate, SCIP_Bool local, SCIP_Bool modifiable, SCIP_Bool dynamic, SCIP_Bool removable, SCIP_Bool stickingatnode) 

SCIP_RETCODE  SCIPcreateConsBasicOrbitope (SCIP *scip, SCIP_CONS **cons, const char *name, SCIP_VAR ***vars, SCIP_Bool ispart, int nspcons, int nblocks, SCIP_Bool resolveprop) 

creates the handler for orbitope constraints and includes it in SCIP
 Parameters

SCIP_RETCODE SCIPcreateConsOrbitope 
( 
SCIP * 
scip, 


SCIP_CONS ** 
cons, 


const char * 
name, 


SCIP_VAR *** 
vars, 


SCIP_Bool 
ispart, 


int 
nspcons, 


int 
nblocks, 


SCIP_Bool 
resolveprop, 


SCIP_Bool 
initial, 


SCIP_Bool 
separate, 


SCIP_Bool 
enforce, 


SCIP_Bool 
check, 


SCIP_Bool 
propagate, 


SCIP_Bool 
local, 


SCIP_Bool 
modifiable, 


SCIP_Bool 
dynamic, 


SCIP_Bool 
removable, 


SCIP_Bool 
stickingatnode 

) 
 
creates and captures a orbitope constraint
 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 
vars  matrix of variables on which the symmetry acts 
ispart  whether we deal with the partitioning case (packing otherwise) 
nspcons  number of set partitioning/packing constraints <=> p 
nblocks  number of symmetric variable blocks <=> q 
resolveprop  should propagation be resolved? 
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. 
modifiable  is constraint modifiable (subject to column generation)? Usually set to FALSE. In column generation applications, set to TRUE if pricing adds coefficients to this constraint. 
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. 
creates and captures an orbitope 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
 SCIPcreateConsOrbitope() for the default constraint flag configuration
 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 
vars  matrix of variables on which the symmetry acts 
ispart  whether we deal with the partitioning case (packing otherwise) 
nspcons  number of set partitioning/packing constraints <=> p 
nblocks  number of symmetric variable blocks <=> q 
resolveprop  should propagation be resolved? 
