/** execution method of primal heuristic */
static
SCIP_DECL_HEUREXEC(heurExecFixandinfer)
{ /*lint --e{715}*/
SCIP_HEURDATA* heurdata;
SCIP_VAR** cands;
int ncands;
int startncands;
int divedepth;
SCIP_Bool cutoff;
SCIP_Real large;
*result = SCIP_DIDNOTRUN;
/* we cannot run on problems with continuous variables */
if( SCIPgetNContVars(scip) > 0 )
return SCIP_OKAY;
/* get unfixed variables */
SCIP_CALL( SCIPgetPseudoBranchCands(scip, &cands, &ncands, NULL) );
if( ncands == 0 )
return SCIP_OKAY;
SCIPdebugMessage("starting fix-and-infer heuristic with %d unfixed integral variables\n", ncands);
*result = SCIP_DIDNOTFIND;
/* get heuristic data */
heurdata = SCIPheurGetData(heur);
assert(heurdata != NULL);
/* start probing */
SCIP_CALL( SCIPstartProbing(scip) );
/* fix variables and propagate inferences as long as the problem is still feasible and there are
* unfixed integral variables
*/
cutoff = FALSE;
divedepth = 0;
startncands = ncands;
/* determine large value to set variables to */
large = SCIPinfinity(scip);
if( !SCIPisInfinity(scip, 0.1 / SCIPfeastol(scip)) )
large = 0.1 / SCIPfeastol(scip);
while( !cutoff && ncands > 0
&& (divedepth < heurdata->minfixings || (startncands - ncands) * 2 * MAXDIVEDEPTH >= startncands * divedepth)
&& !SCIPisStopped(scip) )
{
divedepth++;
/* create next probing node */
SCIP_CALL( SCIPnewProbingNode(scip) );
/* fix next variable */
SCIP_CALL( fixVariable(scip, cands, ncands, large) );
/* propagate the fixing */
SCIP_CALL( SCIPpropagateProbing(scip, heurdata->proprounds, &cutoff, NULL) );
/* get remaining unfixed variables */
if( !cutoff )
{
SCIP_CALL( SCIPgetPseudoBranchCands(scip, &cands, &ncands, NULL) );
}
}
/* check, if we are still feasible */
if( cutoff )
{
SCIPdebugMessage("propagation detected a cutoff\n");
}
else if( ncands == 0 )
{
SCIP_Bool success;
success = FALSE;
/* try to add solution to SCIP */
SCIP_CALL( SCIPtryCurrentSol(scip, heur, FALSE, FALSE, TRUE, &success) );
if( success )
{
SCIPdebugMessage("found primal feasible solution\n");
*result = SCIP_FOUNDSOL;
}
else
{
SCIPdebugMessage("primal solution was rejected\n");
}
}
else
{
SCIPdebugMessage("probing was aborted (probing depth: %d, fixed: %d/%d)", divedepth, startncands - ncands, startncands);
}
/* end probing */
SCIP_CALL( SCIPendProbing(scip) );
return SCIP_OKAY;
}
char constraintPropagation(CPropagation *cp, int var, double value, vector<Fixation> &fixations,
int &unfixedVars, double *colLb, double *colUb, double *constrBound, int *unfixedVarsByRow)
{
assert(value == 0.0 || value == 1.0);
assert(var >= 0 && var < cp->numCols);
//assert(colLb[var] != colUb[var]);
if(colLb[var] == colUb[var])
{
// assert(colLb[var] == value);
return NOIMPLICATION;
}
//assert(fixations.empty());
char status = NOIMPLICATION;
queue<int> C;
Fixation tmp;
vector<char> rowIsInQueue(cp->numRows, 0);
fixVariable(cp, var, value, unfixedVars, colLb, colUb, constrBound, unfixedVarsByRow);
for(int i = 0; i < (int)cp->matrixByCol[var].size(); i++)
{
const pair<int, double> constraint = cp->matrixByCol[var][i];
const int idxRow = constraint.first;
const double coef = constraint.second;
if((unfixedVarsByRow[idxRow] > 0) && (value == 1.0 && coef > 0.0) || (value == 0.0 && coef < 0.0))
{
C.push(idxRow);
rowIsInQueue[idxRow] = 1;
}
}
while(!C.empty())
{
const int idxRow = C.front();
C.pop();
rowIsInQueue[idxRow] = 0;
for(int i = 0; i < (int)cp->matrixByRow[idxRow].size(); i++)
{
const pair<int, double> var = cp->matrixByRow[idxRow][i];
const int idxVar = var.first;
const double coef = var.second;
if(colLb[idxVar] == colUb[idxVar])
continue;
char eval = evaluateBound(cp, var, idxRow, constrBound);
if(eval == ACTIVATE || eval == DEACTIVATE)
{
assert(colLb[idxVar] != colUb[idxVar]);
tmp.idxVar = idxVar;
tmp.valueToFix = eval;
fixations.push_back(tmp);
status = FIXATION;
unfixedVars--;
colLb[idxVar] = colUb[idxVar] = eval;
for(int j = 0; j < (int)cp->matrixByCol[idxVar].size(); j++)
{
const pair<int, double> constraint = cp->matrixByCol[idxVar][j];
const int idxRow2 = constraint.first;
const double coef2 = constraint.second;
unfixedVarsByRow[idxRow2]--;
if(eval == ACTIVATE && coef2 > 0.0)
{
constrBound[idxRow2] -= coef2;
if(unfixedVarsByRow[idxRow2] > 0 && !rowIsInQueue[idxRow2])
{
C.push(idxRow2);
rowIsInQueue[idxRow2] = 1;
}
}
else if(eval == DEACTIVATE && coef2 < 0.0)
{
constrBound[idxRow2] += coef2;
if(unfixedVarsByRow[idxRow2] > 0 && !rowIsInQueue[idxRow2])
{
C.push(idxRow2);
rowIsInQueue[idxRow2] = 1;
}
}
if(unfixedVarsByRow[idxRow2] == 0 && constrBound[idxRow2] < 0.0)
status = CONFLICT; //nao posso retornar direto pq tenho q atualizar os bounds das retricoes
}
if(status == CONFLICT)
return CONFLICT;
}
else if(eval == CONFLICT)
return CONFLICT;
}
}
return status;
}
