/** branches on disjunctive constraint */
static
SCIP_RETCODE branchCons(
SCIP* scip, /**< SCIP data structure */
SCIP_CONS* cons, /**< active disjunction constraint */
SCIP_RESULT* result /**< pointer to store the result */
)
{
SCIP_CONSDATA* consdata;
SCIP_CONS** conss;
SCIP_NODE* child;
SCIP_Real estimate;
int nconss;
int i;
assert(result != NULL);
/* cannot branch on modifiable constraint */
if( SCIPconsIsModifiable(cons) )
return SCIP_OKAY;
consdata = SCIPconsGetData(cons);
assert(consdata != NULL);
conss = consdata->conss;
assert(conss != NULL);
nconss = consdata->nconss;
assert(nconss > 0);
estimate = SCIPgetLocalTransEstimate(scip);
/* add all inactive constraints to local subproblem */
for( i = 0; i < nconss; ++i )
{
/* create the branch-and-bound tree child nodes of the current node */
SCIP_CALL( SCIPcreateChild(scip, &child, 0.0, estimate) );
/* add constraints to nodes */
SCIP_CALL( SCIPaddConsNode(scip, child, conss[i], NULL) );
/* remove disjunction constraint, from child node */
SCIP_CALL( SCIPdelConsNode(scip, child, cons) );
}
/* reset constraint age */
SCIP_CALL( SCIPresetConsAge(scip, cons) );
*result = SCIP_BRANCHED;
return SCIP_OKAY;
}
/** selects a variable out of the given candidate array and performs the branching */
static
SCIP_RETCODE performBranching(
SCIP* scip, /**< SCIP data structure */
SCIP_VAR** cands, /**< candidate array */
SCIP_Real* candsols, /**< array of candidate solution values, or NULL */
int ncands, /**< number of candidates */
SCIP_Real conflictweight, /**< weight in score calculations for conflict score */
SCIP_Real inferenceweight, /**< weight in score calculations for inference score */
SCIP_Real cutoffweight, /**< weight in score calculations for cutoff score */
SCIP_Real reliablescore, /**< score which is seen to be reliable for a branching decision */
SCIP_Bool useweightedsum, /**< should a weighted sum of inference, conflict and cutoff weights be used? */
SCIP_RESULT* result /**< buffer to store result (branched, reduced domain, ...) */
)
{
SCIP_VAR* bestaggrcand;
SCIP_VAR* bestvaluecand;
SCIP_Real bestval;
SCIP_Real bestaggrscore;
SCIP_Real bestvaluescore;
SCIP_Real bestbranchpoint;
SCIP_BRANCHDIR bestbranchdir;
SCIP_NODE* downchild;
SCIP_NODE* eqchild;
SCIP_NODE* upchild;
bestbranchpoint = SCIP_UNKNOWN;
bestbranchdir = SCIP_BRANCHDIR_DOWNWARDS;
bestvaluescore = 0.0;
bestvaluecand = NULL;
assert(ncands > 0);
assert(result != NULL);
*result = SCIP_DIDNOTFIND;
/* check if the weighted sum between the average inferences and conflict score should be used */
if( useweightedsum )
{
int c;
bestaggrcand = cands[0];
bestvaluecand = cands[0];
assert(cands[0] != NULL);
if( candsols == NULL )
{
bestval = SCIP_UNKNOWN;
/* get domain value score for the first candidate */
bestvaluescore = getValueScore(scip, cands[0], conflictweight, cutoffweight, reliablescore, &bestbranchpoint, &bestbranchdir);
SCIPdebugMessage("current best value candidate <%s>[%g,%g] %s <%g> (value %g)\n",
SCIPvarGetName(bestvaluecand), SCIPvarGetLbLocal(bestvaluecand), SCIPvarGetUbLocal(bestvaluecand),
bestbranchdir == SCIP_BRANCHDIR_DOWNWARDS ? "<=" : ">=", bestbranchpoint, bestvaluescore);
}
else
bestval = candsols[0];
/* get aggregated score for the first candidate */
bestaggrscore = getAggrScore(scip, cands[0], conflictweight, inferenceweight, cutoffweight, reliablescore);
for( c = 1; c < ncands; ++c )
{
SCIP_VAR* cand;
SCIP_Real val;
SCIP_Real aggrscore;
SCIP_Real branchpoint;
SCIP_BRANCHDIR branchdir;
cand = cands[c];
assert(cand != NULL);
if( candsols == NULL )
{
SCIP_Real valuescore;
val = SCIP_UNKNOWN;
/* get domain value score for the candidate */
valuescore = getValueScore(scip, cand, conflictweight, cutoffweight, reliablescore, &branchpoint, &branchdir);
/* evaluate the candidate against the currently best candidate w.r.t. domain value score */
evaluateValueCand(cand, valuescore, branchpoint, branchdir, &bestvaluecand, &bestvaluescore, &bestbranchpoint, &bestbranchdir);
SCIPdebugMessage("current best value candidate <%s>[%g,%g] %s <%g> (value %g)\n",
SCIPvarGetName(bestvaluecand), SCIPvarGetLbLocal(bestvaluecand), SCIPvarGetUbLocal(bestvaluecand),
bestbranchdir == SCIP_BRANCHDIR_DOWNWARDS ? "<=" : ">=", bestbranchpoint, bestvaluescore);
}
else
val = candsols[c];
/* get aggregated score for the candidate */
aggrscore = getAggrScore(scip, cand, conflictweight, inferenceweight, cutoffweight, reliablescore);
SCIPdebugMessage(" -> cand <%s>: prio=%d, solval=%g, score=%g\n", SCIPvarGetName(cand), SCIPvarGetBranchPriority(cand),
val == SCIP_UNKNOWN ? SCIPgetVarSol(scip, cand) : val, aggrscore); /*lint !e777*/
/* evaluate the candidate against the currently best candidate w.r.t. aggregated score */
evaluateAggrCand(cand, aggrscore, val, &bestaggrcand, &bestaggrscore, &bestval);
}
}
else
{
int c;
bestaggrcand = cands[0];
assert(cands[0] != NULL);
if( candsols != NULL )
bestval = candsols[0];
else
bestval = SCIP_UNKNOWN;
bestaggrscore = SCIPgetVarAvgInferenceScore(scip, cands[0]);
/* search for variable with best score w.r.t. average inferences per branching */
for( c = 1; c < ncands; ++c )
{
SCIP_VAR* cand;
SCIP_Real val;
SCIP_Real aggrscore;
cand = cands[c];
assert(cand != NULL);
if( candsols != NULL )
val = candsols[c];
else
val = SCIP_UNKNOWN;
aggrscore = SCIPgetVarAvgInferenceScore(scip, cand);
/* in case the average inferences score is below the reliable score we set it to zero since it is seen to be
* unreliable
*/
if( aggrscore < reliablescore )
aggrscore = 0.0;
SCIPdebugMessage(" -> cand <%s>: prio=%d, solval=%g, score=%g\n", SCIPvarGetName(cand), SCIPvarGetBranchPriority(cand),
val == SCIP_UNKNOWN ? SCIPgetVarSol(scip, cand) : val, aggrscore); /*lint !e777*/
/* evaluate the candidate against the currently best candidate */
evaluateAggrCand(cand, aggrscore, val, &bestaggrcand, &bestaggrscore, &bestval);
}
}
assert(bestaggrcand != NULL);
SCIPdebugMessage(" -> %d candidates, selected variable <%s>[%g,%g] (prio=%d, solval=%.12f, score=%g, conflict=%g cutoff=%g, inference=%g)\n",
ncands, SCIPvarGetName(bestaggrcand), SCIPvarGetLbLocal (bestaggrcand), SCIPvarGetUbLocal(bestaggrcand), SCIPvarGetBranchPriority(bestaggrcand),
bestval == SCIP_UNKNOWN ? SCIPgetVarSol(scip, bestaggrcand) : bestval, bestaggrscore, /*lint !e777*/
SCIPgetVarConflictScore(scip, bestaggrcand), SCIPgetVarAvgInferenceCutoffScore(scip, bestaggrcand, cutoffweight),
SCIPgetVarAvgInferenceScore(scip, bestaggrcand));
/* perform the branching */
if( candsols != NULL )
{
SCIP_CALL( SCIPbranchVarVal(scip, bestaggrcand, SCIPgetBranchingPoint(scip, bestaggrcand, bestval), &downchild, &eqchild, &upchild) );
}
else if( bestbranchpoint == SCIP_UNKNOWN ) /*lint !e777*/
{
SCIP_CALL( SCIPbranchVar(scip, bestaggrcand, &downchild, &eqchild, &upchild) );
}
else
{
SCIP_Real estimate;
SCIP_Real downprio;
SCIP_Real upprio;
SCIP_Real downub;
SCIP_Real uplb;
assert(bestvaluecand != NULL);
downprio = 0.0;
upprio = 0.0;
if( bestbranchdir == SCIP_BRANCHDIR_DOWNWARDS )
{
downprio = 1.0;
downub = bestbranchpoint;
uplb = bestbranchpoint + 1.0;
}
else
{
upprio = 1.0;
downub = bestbranchpoint - 1.0;
uplb = bestbranchpoint;
}
/* calculate the child estimate */
estimate = SCIPcalcChildEstimate(scip, bestvaluecand, downub);
/* create down child */
SCIP_CALL( SCIPcreateChild(scip, &downchild, downprio, estimate) );
/* change upper bound in down child */
SCIP_CALL( SCIPchgVarUbNode(scip, downchild, bestvaluecand, downub) );
/* calculate the child estimate */
estimate = SCIPcalcChildEstimate(scip, bestvaluecand, uplb);
/* create up child */
SCIP_CALL( SCIPcreateChild(scip, &upchild, upprio, estimate) );
/* change lower bound in up child */
SCIP_CALL( SCIPchgVarLbNode(scip, upchild, bestvaluecand, uplb) );
SCIPdebugMessage("branch on variable <%s> and value <%g>\n", SCIPvarGetName(bestvaluecand), bestbranchpoint);
eqchild = NULL;
}
if( downchild != NULL || eqchild != NULL || upchild != NULL )
{
*result = SCIP_BRANCHED;
}
else
{
/* if there are no children, then variable should have been fixed by SCIPbranchVar(Val) */
assert(SCIPisEQ(scip, SCIPvarGetLbLocal(bestaggrcand), SCIPvarGetUbLocal(bestaggrcand)));
*result = SCIP_REDUCEDDOM;
}
return SCIP_OKAY;
}
/** branching execution method for fractional LP solutions */
static
SCIP_DECL_BRANCHEXECLP(branchExeclpStp)
{ /*lint --e{715}*/
SCIP_PROBDATA* probdata;
SCIP_CONS* consin;
SCIP_CONS* consout;
SCIP_NODE* vertexin;
SCIP_NODE* vertexout;
SCIP_VAR** edgevars;
SCIP_Real estimatein;
SCIP_Real estimateout;
GRAPH* g;
int e;
int branchvertex;
assert(branchrule != NULL);
assert(strcmp(SCIPbranchruleGetName(branchrule), BRANCHRULE_NAME) == 0);
assert(scip != NULL);
assert(result != NULL);
SCIPdebugMessage("Execlp method of Stp branching\n ");
estimatein = SCIPgetUpperbound(scip);
estimateout = SCIPgetUpperbound(scip);
*result = SCIP_DIDNOTRUN;
/* get problem data */
probdata = SCIPgetProbData(scip);
assert(probdata != NULL);
/* get graph */
g = SCIPprobdataGetGraph(probdata);
assert(g != NULL);
/* get vertex to branch on */
SCIP_CALL( selectBranchingVertex(scip, &branchvertex) );
if( branchvertex == UNKNOWN )
{
SCIPdebugMessage("Branching did not run \n");
return SCIP_OKAY;
}
edgevars = SCIPprobdataGetEdgeVars(scip);
/* create constraints */
SCIP_CALL( SCIPcreateConsLinear(scip, &consin, "consin", 0,
NULL, NULL, 1.0, 1.0,
TRUE, TRUE, FALSE, FALSE, TRUE, TRUE, FALSE, FALSE, FALSE, TRUE) );
SCIP_CALL( SCIPcreateConsLinear(scip, &consout, "consout", 0,
NULL, NULL, 0.0, 0.0,
TRUE, TRUE, FALSE, FALSE, TRUE, TRUE, FALSE, FALSE, FALSE, TRUE) );
for( e = g->inpbeg[branchvertex]; e != EAT_LAST; e = g->ieat[e] )
{
SCIP_CALL( SCIPaddCoefLinear(scip, consin, edgevars[e], 1.0) );
SCIP_CALL( SCIPaddCoefLinear(scip, consout, edgevars[e], 1.0) );
SCIP_CALL( SCIPaddCoefLinear(scip, consout, edgevars[flipedge(e)], 1.0) );
}
/* create the child nodes */
SCIP_CALL( SCIPcreateChild(scip, &vertexin, 1.0, estimatein) );
SCIP_CALL( SCIPcreateChild(scip, &vertexout, 1.0, estimateout) );
assert(vertexin != NULL);
assert(vertexout != NULL);
SCIP_CALL( SCIPaddConsNode(scip, vertexin, consin, NULL) );
SCIP_CALL( SCIPaddConsNode(scip, vertexout, consout, NULL) );
/* relase constraints */
SCIP_CALL( SCIPreleaseCons(scip, &consin) );
SCIP_CALL( SCIPreleaseCons(scip, &consout) );
SCIPdebugMessage("Branched on stp vertex %d \n", branchvertex);
*result = SCIP_BRANCHED;
return SCIP_OKAY;
}
