/** creates and captures a variable bound constraint: lhs <= x + c*y <= rhs
*
* @note the constraint gets captured, hence at one point you have to release it using the method {@link releaseCons()}
*/
JNIEXPORT
jlong JNISCIPCONSVARBOUND(createConsVarbound)(
JNIEnv* env, /**< JNI environment variable */
jobject jobj, /**< JNI class pointer */
jlong jscip, /**< SCIP data structure */
jstring jname, /**< name of constraint */
jlong jvar, /**< variable x that has variable bound */
jlong jvbdvar, /**< binary, integer or implicit integer bounding variable y */
jdouble jvbdcoef, /**< coefficient c of bounding variable y */
jdouble jlhs, /**< left hand side of variable bound inequality */
jdouble jrhs, /**< right hand side of variable bound inequality */
jboolean jinitial, /**< should the LP relaxation of constraint be in the initial LP?
* Usually set to TRUE. Set to FALSE for 'lazy constraints'. */
jboolean jseparate, /**< should the constraint be separated during LP processing?
* Usually set to TRUE. */
jboolean jenforce, /**< should the constraint be enforced during node processing?
* TRUE for model constraints, FALSE for additional, redundant constraints. */
jboolean jcheck, /**< should the constraint be checked for feasibility?
* TRUE for model constraints, FALSE for additional, redundant constraints. */
jboolean jpropagate, /**< should the constraint be propagated during node processing?
* Usually set to TRUE. */
jboolean jlocal, /**< is constraint only valid locally?
* Usually set to FALSE. Has to be set to TRUE, e.g., for branching constraints. */
jboolean jmodifiable, /**< 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. */
jboolean jdynamic, /**< is constraint subject to aging?
* Usually set to FALSE. Set to TRUE for own cuts which
* are seperated as constraints. */
jboolean jremovable, /**< 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'. */
jboolean jstickingatnode /**< 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* scip;
SCIP_CONS* cons;
const char* name;
SCIP_VAR* var;
SCIP_VAR* vbdvar;
jboolean iscopy;
/* convert JNI pointer into C pointer */
scip = (SCIP*) (size_t) jscip;
assert(scip != NULL);
/* convert JNI string into C const char* */
name = (*env)->GetStringUTFChars(env, jname, &iscopy);
if( name == NULL )
SCIPABORT();
assert(iscopy);
/* convert JNI pointer into C pointer */
var = (SCIP_VAR*) (size_t) jvar;
assert(var != NULL);
/* convert JNI pointer into C pointer */
vbdvar = (SCIP_VAR*) (size_t) jvbdvar;
assert(vbdvar != NULL);
JNISCIP_CALL( SCIPcreateConsVarbound(scip, &cons, name, var, vbdvar, (SCIP_Real)jvbdcoef, (SCIP_Real)jlhs, (SCIP_Real)jrhs, (SCIP_Bool) jinitial, (SCIP_Bool) jseparate, (SCIP_Bool) jenforce, (SCIP_Bool) jcheck, (SCIP_Bool) jpropagate,
(SCIP_Bool) jlocal, (SCIP_Bool) jmodifiable, (SCIP_Bool) jdynamic, (SCIP_Bool) jremovable, (SCIP_Bool) jstickingatnode) );
(*env)->ReleaseStringUTFChars(env, jname, name);
return (jlong)(size_t)cons;
}
/** add branching decisions constraints to the sub SCIP */
static
SCIP_RETCODE addBranchingDecisionConss(
SCIP* scip, /**< SCIP data structure */
SCIP* subscip, /**< pricing SCIP data structure */
SCIP_VAR** vars, /**< variable array of the subscuip oder variables */
SCIP_CONSHDLR* conshdlr /**< constraint handler for branching data */
) {
SCIP_CONS** conss;
SCIP_CONS* cons;
int nconss;
int id1;
int id2;
CONSTYPE type;
SCIP_Real vbdcoef;
SCIP_Real lhs;
SCIP_Real rhs;
int c;
assert(scip != NULL);
assert(subscip != NULL);
assert(conshdlr != NULL);
/* collect all branching decision constraints */
conss = SCIPconshdlrGetConss(conshdlr);
nconss = SCIPconshdlrGetNConss(conshdlr);
/* loop over all branching decision constraints and apply the branching decision if the corresponding constraint is active */
for (c = 0; c < nconss; ++c) {
cons = conss[c];
/* ignore constraints which are not active since these are not laying on the current active path of the search tree */
if (!SCIPconsIsActive(cons))
continue;
/* collect the two item ids and the branching type (SAME or DIFFER) on which the constraint branched */
id1 = SCIPgetItemid1Samediff(scip, cons);
id2 = SCIPgetItemid2Samediff(scip, cons);
type = SCIPgetTypeSamediff(scip, cons);
SCIPdebugMessage("create varbound for %s(%d,%d)\n", type == SAME ? "same" : "diff",
SCIPprobdataGetIds(SCIPgetProbData(scip))[id1], SCIPprobdataGetIds(SCIPgetProbData(scip))[id2]);
/* depending on the branching type select the correct left and right hand side for the linear constraint which
* enforces this branching decision in the pricing problem MIP
*/
if (type == SAME) {
lhs = 0.0;
rhs = 0.0;
vbdcoef = -1.0;
} else if (type == DIFFER) {
lhs = -SCIPinfinity(scip);
rhs = 1.0;
vbdcoef = 1.0;
} else {
SCIPerrorMessage("unknow constraint type <%d>\n, type");
return SCIP_INVALIDDATA;
}
/* add linear (in that case a variable bound) constraint to pricing MIP depending on the branching type:
*
* - branching type SAME: x1 = x2 <=> x1 - x2 = 0 <=> 0 <= x1 - x2 <= 0
*
* - branching type DIFFER: x1 - x2 <= 1 <=> -inf <= x1 - x2 <= 1
*
*/
SCIP_CALL(SCIPcreateConsVarbound(subscip, &cons, SCIPconsGetName(conss[c]),
vars[id1], vars[id2], vbdcoef, lhs, rhs, // TODO: Alert! id1 and id2 might not be the correct indices of the vars (if some constraints are skipped)
TRUE, TRUE, TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE));
SCIPdebug(SCIPprintCons(subscip, cons, NULL));
SCIP_CALL(SCIPaddCons(subscip, cons));
SCIP_CALL(SCIPreleaseCons(subscip, &cons));
}
return SCIP_OKAY;
}
/** creates a cumulative scheduling problem */
SCIP_RETCODE SCIPcreateSchedulingProblem(
SCIP* scip, /**< SCIP data structure */
const char* problemname, /**< problem name */
const char** jobnames, /**< job names, or NULL */
const char** resourcenames, /**< resource names, or NULL */
int** demands, /**< demand matrix resource job demand */
SCIP_DIGRAPH* precedencegraph, /**< direct graph to store the precedence conditions */
int* durations, /**< array to store the processing for each job */
int* capacities, /**< array to store the different capacities */
int njobs, /**< number of jobs to be parsed */
int nresources /**< number of capacities to be parsed */
)
{
SCIP_VAR** jobs;
SCIP_VAR** vars;
SCIP_VAR* var;
SCIP_CONS* cons;
char name[SCIP_MAXSTRLEN];
int* consdurations;
int* consdemands;
int nvars;
int ubmakespan;
int i;
int j;
int r;
assert( scip != NULL );
assert( njobs >= 0 );
SCIPdebugMessage( "start method SCIPcreateSchedulingSMProblem\n");
/* create SCIP data structure */
SCIP_CALL( SCIPcreateProb(scip, problemname, NULL, NULL, NULL, NULL, NULL, NULL, NULL) );
/* compute a feasible upper bound on the makespan */
ubmakespan = computeUbmakespan(durations, njobs);
ubmakespan *= 100;
/* allocate buffer for jobs and precedence constraints */
SCIP_CALL( SCIPallocBufferArray(scip, &jobs, njobs) );
/* create an activity constraint for each activity */
for( j = 0; j < njobs - 1; ++j ) /* but not for last job which is the makespan (-1) */
{
/* construct variable name */
if( jobnames != NULL )
(void)SCIPsnprintf(name, SCIP_MAXSTRLEN, "start_%s", jobnames[j]);
else
(void)SCIPsnprintf(name, SCIP_MAXSTRLEN, "start_%d", j);
/* create integer starting variable */
SCIP_CALL( SCIPcreateVar(scip, &var, name, 0.0, (SCIP_Real)ubmakespan, 0.0, SCIP_VARTYPE_INTEGER,
TRUE, FALSE, NULL, NULL, NULL, NULL, NULL) );
SCIP_CALL( SCIPaddVar(scip, var) );
SCIP_CALL( SCIPmarkDoNotMultaggrVar(scip, var) );
jobs[j] = var;
SCIP_CALL( SCIPreleaseVar(scip, &var) );
}
/* create makespan variable */
SCIP_CALL( SCIPcreateVar(scip, &var, "makespan", 0.0, (SCIP_Real)ubmakespan, 1.0, SCIP_VARTYPE_INTEGER,
TRUE, FALSE, NULL, NULL, NULL, NULL, NULL) );
SCIP_CALL( SCIPaddVar(scip, var) );
SCIP_CALL( SCIPmarkDoNotMultaggrVar(scip, var) );
jobs[njobs-1] = var;
SCIP_CALL( SCIPreleaseVar(scip, &var) );
/* precedence constraints */
for( j = 0; j < njobs - 1; ++j )
{
SCIP_VAR* predvar;
int nsuccessors;
nsuccessors = SCIPdigraphGetNSuccessors(precedencegraph, j);
predvar = jobs[j];
assert(predvar != NULL);
if( nsuccessors > 0 )
{
int* successors;
void** distances;
successors = SCIPdigraphGetSuccessors(precedencegraph, j);
distances = SCIPdigraphGetSuccessorsDatas(precedencegraph, j);
for( i = 0; i < nsuccessors; ++i )
{
SCIP_VAR* succvar;
int distance;
succvar = jobs[successors[i]];
assert(succvar != NULL);
(void)SCIPsnprintf(name, SCIP_MAXSTRLEN, "precedences_(%d,%d)", j, successors[i]);
distance = (int)(size_t)distances[i];
if( distance == INT_MAX )
distance = durations[j];
SCIP_CALL( SCIPcreateConsVarbound(scip, &cons, name, predvar, succvar, -1.0,
-SCIPinfinity(scip), -distance,
TRUE, TRUE, TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE) );
SCIP_CALL( SCIPaddCons(scip, cons) );
SCIP_CALL( SCIPreleaseCons(scip, &cons) );
}
}
else
{
/* add precedence constraints for those jobs without successor */
(void)SCIPsnprintf(name, SCIP_MAXSTRLEN, "precedences_(%d,%d)", j, njobs);
SCIP_CALL( SCIPcreateConsVarbound(scip, &cons, name, predvar, jobs[njobs-1], -1.0,
-SCIPinfinity(scip), -durations[j],
TRUE, TRUE, TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE) );
SCIP_CALL( SCIPaddCons(scip, cons) );
SCIP_CALL( SCIPreleaseCons(scip, &cons) );
}
}
SCIP_CALL( SCIPallocBufferArray(scip, &vars, njobs) );
SCIP_CALL( SCIPallocBufferArray(scip, &consdemands, njobs) );
SCIP_CALL( SCIPallocBufferArray(scip, &consdurations, njobs) );
/* create resource constraints */
for( r = 0; r < nresources; ++r )
{
nvars = 0;
for( j = 0; j < njobs; ++j ) /* also makespan constraint! */
{
if( demands[j][r] > 0 )
{
vars[nvars] = jobs[j];
consdemands[nvars] = demands[j][r];
consdurations[nvars] = durations[j];
nvars++;
}
}
if( nvars > 0 )
{
/* construct constraint name */
if( resourcenames != NULL )
(void)SCIPsnprintf(name, SCIP_MAXSTRLEN, "R%s", resourcenames[r]);
else
(void)SCIPsnprintf(name, SCIP_MAXSTRLEN, "R%d", r);
SCIP_CALL( SCIPcreateConsCumulative(scip, &cons, name,
nvars, vars, consdurations, consdemands, capacities[r],
TRUE, TRUE, TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE) );
SCIP_CALL( SCIPaddCons(scip, cons) );
SCIP_CALL( SCIPreleaseCons(scip, &cons) );
}
}
/* initialize the problem specific heuristic */
SCIP_CALL( SCIPinitializeHeurListScheduling(scip, precedencegraph, jobs,
durations, demands, capacities, njobs, nresources) );
/* free buffer array */
SCIPfreeBufferArray(scip, &consdurations);
SCIPfreeBufferArray(scip, &consdemands);
SCIPfreeBufferArray(scip, &vars);
SCIPfreeBufferArray(scip, &jobs);
return SCIP_OKAY;
}