/** LP solution separation method for disjunctive cuts */
static
SCIP_DECL_SEPAEXECLP(sepaExeclpDisjunctive)
{
SCIP_SEPADATA* sepadata;
SCIP_CONSHDLR* conshdlr;
SCIP_DIGRAPH* conflictgraph;
SCIP_ROW** rows;
SCIP_COL** cols;
SCIP_Real* cutcoefs = NULL;
SCIP_Real* simplexcoefs1 = NULL;
SCIP_Real* simplexcoefs2 = NULL;
SCIP_Real* coef = NULL;
SCIP_Real* binvrow = NULL;
SCIP_Real* rowsmaxval = NULL;
SCIP_Real* violationarray = NULL;
int* fixings1 = NULL;
int* fixings2 = NULL;
int* basisind = NULL;
int* basisrow = NULL;
int* varrank = NULL;
int* edgearray = NULL;
int nedges;
int ndisjcuts;
int nrelevantedges;
int nsos1vars;
int nconss;
int maxcuts;
int ncalls;
int depth;
int ncols;
int nrows;
int ind;
int j;
int i;
assert( sepa != NULL );
assert( strcmp(SCIPsepaGetName(sepa), SEPA_NAME) == 0 );
assert( scip != NULL );
assert( result != NULL );
*result = SCIP_DIDNOTRUN;
/* only generate disjunctive cuts if we are not close to terminating */
if ( SCIPisStopped(scip) )
return SCIP_OKAY;
/* only generate disjunctive cuts if an optimal LP solution is at hand */
if ( SCIPgetLPSolstat(scip) != SCIP_LPSOLSTAT_OPTIMAL )
return SCIP_OKAY;
/* only generate disjunctive cuts if the LP solution is basic */
if ( ! SCIPisLPSolBasic(scip) )
return SCIP_OKAY;
/* get LP data */
SCIP_CALL( SCIPgetLPColsData(scip, &cols, &ncols) );
SCIP_CALL( SCIPgetLPRowsData(scip, &rows, &nrows) );
/* return if LP has no columns or no rows */
if ( ncols == 0 || nrows == 0 )
return SCIP_OKAY;
assert( cols != NULL );
assert( rows != NULL );
/* get sepa data */
sepadata = SCIPsepaGetData(sepa);
assert( sepadata != NULL );
/* get constraint handler */
conshdlr = sepadata->conshdlr;
if ( conshdlr == NULL )
return SCIP_OKAY;
/* get number of constraints */
nconss = SCIPconshdlrGetNConss(conshdlr);
if ( nconss == 0 )
return SCIP_OKAY;
/* check for maxdepth < depth, maxinvcutsroot = 0 and maxinvcuts = 0 */
depth = SCIPgetDepth(scip);
if ( ( sepadata->maxdepth >= 0 && sepadata->maxdepth < depth )
|| ( depth == 0 && sepadata->maxinvcutsroot == 0 )
|| ( depth > 0 && sepadata->maxinvcuts == 0 ) )
return SCIP_OKAY;
/* only call the cut separator a given number of times at each node */
ncalls = SCIPsepaGetNCallsAtNode(sepa);
if ( (depth == 0 && sepadata->maxroundsroot >= 0 && ncalls >= sepadata->maxroundsroot)
|| (depth > 0 && sepadata->maxrounds >= 0 && ncalls >= sepadata->maxrounds) )
return SCIP_OKAY;
/* get conflict graph and number of conflict graph edges (note that the digraph arcs were added in both directions) */
conflictgraph = SCIPgetConflictgraphSOS1(conshdlr);
nedges = (int)SCIPceil(scip, (SCIP_Real)SCIPdigraphGetNArcs(conflictgraph)/2);
/* if too many conflict graph edges, the separator can be slow: delay it until no other cuts have been found */
if ( sepadata->maxconfsdelay >= 0 && nedges >= sepadata->maxconfsdelay )
{
int ncutsfound;
ncutsfound = SCIPgetNCutsFound(scip);
if ( ncutsfound > sepadata->lastncutsfound || ! SCIPsepaWasLPDelayed(sepa) )
{
sepadata->lastncutsfound = ncutsfound;
*result = SCIP_DELAYED;
return SCIP_OKAY;
}
}
/* check basis status */
for (j = 0; j < ncols; ++j)
{
if ( SCIPcolGetBasisStatus(cols[j]) == SCIP_BASESTAT_ZERO )
return SCIP_OKAY;
}
/* get number of SOS1 variables */
nsos1vars = SCIPgetNSOS1Vars(conshdlr);
/* allocate buffer arrays */
SCIP_CALL( SCIPallocBufferArray(scip, &edgearray, nedges) );
SCIP_CALL( SCIPallocBufferArray(scip, &fixings1, nedges) );
SCIP_CALL( SCIPallocBufferArray(scip, &fixings2, nedges) );
SCIP_CALL( SCIPallocBufferArray(scip, &violationarray, nedges) );
/* get all violated conflicts {i, j} in the conflict graph and sort them based on the degree of a violation value */
nrelevantedges = 0;
for (j = 0; j < nsos1vars; ++j)
{
SCIP_VAR* var;
var = SCIPnodeGetVarSOS1(conflictgraph, j);
if ( SCIPvarIsActive(var) && ! SCIPisFeasZero(scip, SCIPcolGetPrimsol(SCIPvarGetCol(var))) && SCIPcolGetBasisStatus(SCIPvarGetCol(var)) == SCIP_BASESTAT_BASIC )
{
int* succ;
int nsucc;
/* get successors and number of successors */
nsucc = SCIPdigraphGetNSuccessors(conflictgraph, j);
succ = SCIPdigraphGetSuccessors(conflictgraph, j);
for (i = 0; i < nsucc; ++i)
{
SCIP_VAR* varsucc;
int succind;
succind = succ[i];
varsucc = SCIPnodeGetVarSOS1(conflictgraph, succind);
if ( SCIPvarIsActive(varsucc) && succind < j && ! SCIPisFeasZero(scip, SCIPgetSolVal(scip, NULL, varsucc) ) &&
SCIPcolGetBasisStatus(SCIPvarGetCol(varsucc)) == SCIP_BASESTAT_BASIC )
{
fixings1[nrelevantedges] = j;
fixings2[nrelevantedges] = succind;
edgearray[nrelevantedges] = nrelevantedges;
violationarray[nrelevantedges++] = SCIPgetSolVal(scip, NULL, var) * SCIPgetSolVal(scip, NULL, varsucc);
}
}
}
}
/* sort violation score values */
if ( nrelevantedges > 0)
SCIPsortDownRealInt(violationarray, edgearray, nrelevantedges);
else
{
SCIPfreeBufferArrayNull(scip, &violationarray);
SCIPfreeBufferArrayNull(scip, &fixings2);
SCIPfreeBufferArrayNull(scip, &fixings1);
SCIPfreeBufferArrayNull(scip, &edgearray);
return SCIP_OKAY;
}
SCIPfreeBufferArrayNull(scip, &violationarray);
/* compute maximal number of cuts */
if ( SCIPgetDepth(scip) == 0 )
maxcuts = MIN(sepadata->maxinvcutsroot, nrelevantedges);
else
maxcuts = MIN(sepadata->maxinvcuts, nrelevantedges);
assert( maxcuts > 0 );
/* allocate buffer arrays */
SCIP_CALL( SCIPallocBufferArray(scip, &varrank, ncols) );
SCIP_CALL( SCIPallocBufferArray(scip, &rowsmaxval, nrows) );
SCIP_CALL( SCIPallocBufferArray(scip, &basisrow, ncols) );
SCIP_CALL( SCIPallocBufferArray(scip, &binvrow, nrows) );
SCIP_CALL( SCIPallocBufferArray(scip, &coef, ncols) );
SCIP_CALL( SCIPallocBufferArray(scip, &simplexcoefs1, ncols) );
SCIP_CALL( SCIPallocBufferArray(scip, &simplexcoefs2, ncols) );
SCIP_CALL( SCIPallocBufferArray(scip, &cutcoefs, ncols) );
SCIP_CALL( SCIPallocBufferArray(scip, &basisind, nrows) );
/* get basis indices */
SCIP_CALL( SCIPgetLPBasisInd(scip, basisind) );
/* create vector "basisrow" with basisrow[column of non-slack basis variable] = corresponding row of B^-1;
* compute maximum absolute value of nonbasic row coefficients */
for (j = 0; j < nrows; ++j)
{
SCIP_COL** rowcols;
SCIP_Real* rowvals;
SCIP_ROW* row;
SCIP_Real val;
SCIP_Real max = 0.0;
int nnonz;
/* fill basisrow vector */
ind = basisind[j];
if ( ind >= 0 )
basisrow[ind] = j;
/* compute maximum absolute value of nonbasic row coefficients */
row = rows[j];
assert( row != NULL );
rowvals = SCIProwGetVals(row);
nnonz = SCIProwGetNNonz(row);
rowcols = SCIProwGetCols(row);
for (i = 0; i < nnonz; ++i)
{
if ( SCIPcolGetBasisStatus(rowcols[i]) == SCIP_BASESTAT_LOWER || SCIPcolGetBasisStatus(rowcols[i]) == SCIP_BASESTAT_UPPER )
{
val = REALABS(rowvals[i]);
if ( SCIPisFeasGT(scip, val, max) )
max = REALABS(val);
}
}
/* handle slack variable coefficient and save maximum value */
rowsmaxval[j] = MAX(max, 1.0);
}
/* initialize variable ranks with -1 */
for (j = 0; j < ncols; ++j)
varrank[j] = -1;
/* free buffer array */
SCIPfreeBufferArrayNull(scip, &basisind);
/* for the most promising disjunctions: try to generate disjunctive cuts */
ndisjcuts = 0;
for (i = 0; i < maxcuts; ++i)
{
SCIP_Bool madeintegral;
SCIP_Real cutlhs1;
SCIP_Real cutlhs2;
SCIP_Real bound1;
SCIP_Real bound2;
SCIP_ROW* row = NULL;
SCIP_VAR* var;
SCIP_COL* col;
int nonbasicnumber;
int cutrank = 0;
int edgenumber;
int rownnonz;
edgenumber = edgearray[i];
/* determine first simplex row */
var = SCIPnodeGetVarSOS1(conflictgraph, fixings1[edgenumber]);
col = SCIPvarGetCol(var);
ind = SCIPcolGetLPPos(col);
assert( ind >= 0 );
assert( SCIPcolGetBasisStatus(col) == SCIP_BASESTAT_BASIC );
/* get the 'ind'th row of B^-1 and B^-1 \cdot A */
SCIP_CALL( SCIPgetLPBInvRow(scip, basisrow[ind], binvrow, NULL, NULL) );
SCIP_CALL( SCIPgetLPBInvARow(scip, basisrow[ind], binvrow, coef, NULL, NULL) );
/* get the simplex-coefficients of the non-basic variables */
SCIP_CALL( getSimplexCoefficients(scip, rows, nrows, cols, ncols, coef, binvrow, simplexcoefs1, &nonbasicnumber) );
/* get rank of variable if not known already */
if ( varrank[ind] < 0 )
varrank[ind] = getVarRank(scip, binvrow, rowsmaxval, sepadata->maxweightrange, rows, nrows);
cutrank = MAX(cutrank, varrank[ind]);
/* get right hand side and bound of simplex talbeau row */
cutlhs1 = SCIPcolGetPrimsol(col);
if ( SCIPisFeasPositive(scip, cutlhs1) )
bound1 = SCIPcolGetUb(col);
else
bound1 = SCIPcolGetLb(col);
/* determine second simplex row */
var = SCIPnodeGetVarSOS1(conflictgraph, fixings2[edgenumber]);
col = SCIPvarGetCol(var);
ind = SCIPcolGetLPPos(col);
assert( ind >= 0 );
assert( SCIPcolGetBasisStatus(col) == SCIP_BASESTAT_BASIC );
/* get the 'ind'th row of B^-1 and B^-1 \cdot A */
SCIP_CALL( SCIPgetLPBInvRow(scip, basisrow[ind], binvrow, NULL, NULL) );
SCIP_CALL( SCIPgetLPBInvARow(scip, basisrow[ind], binvrow, coef, NULL, NULL) );
/* get the simplex-coefficients of the non-basic variables */
SCIP_CALL( getSimplexCoefficients(scip, rows, nrows, cols, ncols, coef, binvrow, simplexcoefs2, &nonbasicnumber) );
/* get rank of variable if not known already */
if ( varrank[ind] < 0 )
varrank[ind] = getVarRank(scip, binvrow, rowsmaxval, sepadata->maxweightrange, rows, nrows);
cutrank = MAX(cutrank, varrank[ind]);
/* get right hand side and bound of simplex talbeau row */
cutlhs2 = SCIPcolGetPrimsol(col);
if ( SCIPisFeasPositive(scip, cutlhs2) )
bound2 = SCIPcolGetUb(col);
else
bound2 = SCIPcolGetLb(col);
/* add coefficients to cut */
SCIP_CALL( generateDisjCutSOS1(scip, sepa, rows, nrows, cols, ncols, ndisjcuts, TRUE, sepadata->strengthen, cutlhs1, cutlhs2, bound1, bound2, simplexcoefs1, simplexcoefs2, cutcoefs, &row, &madeintegral) );
if ( row == NULL )
continue;
/* raise cutrank for present cut */
++cutrank;
/* check if there are numerical evidences */
if ( ( madeintegral && ( sepadata->maxrankintegral == -1 || cutrank <= sepadata->maxrankintegral ) )
|| ( ! madeintegral && ( sepadata->maxrank == -1 || cutrank <= sepadata->maxrank ) ) )
{
/* possibly add cut to LP if it is useful; in case the lhs of the cut is minus infinity (due to scaling) the cut is useless */
rownnonz = SCIProwGetNNonz(row);
if ( rownnonz > 0 && ! SCIPisInfinity(scip, -SCIProwGetLhs(row)) && ! SCIProwIsInLP(row) && SCIPisCutEfficacious(scip, NULL, row) )
{
SCIP_Bool infeasible;
/* set cut rank */
SCIProwChgRank(row, cutrank);
/* add cut */
SCIP_CALL( SCIPaddCut(scip, NULL, row, FALSE, &infeasible) );
SCIPdebug( SCIP_CALL( SCIPprintRow(scip, row, NULL) ) );
if ( infeasible )
{
*result = SCIP_CUTOFF;
break;
}
++ndisjcuts;
}
}
/* release row */
SCIP_CALL( SCIPreleaseRow(scip, &row) );
}
/* save total number of cuts found so far */
sepadata->lastncutsfound = SCIPgetNCutsFound(scip);
/* evaluate the result of the separation */
if ( *result != SCIP_CUTOFF )
{
if ( ndisjcuts > 0 )
*result = SCIP_SEPARATED;
else
*result = SCIP_DIDNOTFIND;
}
SCIPdebugMessage("Number of found disjunctive cuts: %d.\n", ndisjcuts);
/* free buffer arrays */
SCIPfreeBufferArrayNull(scip, &cutcoefs);
SCIPfreeBufferArrayNull(scip, &simplexcoefs2);
SCIPfreeBufferArrayNull(scip, &simplexcoefs1);
SCIPfreeBufferArrayNull(scip, &coef);
SCIPfreeBufferArrayNull(scip, &binvrow);
SCIPfreeBufferArrayNull(scip, &basisrow);
SCIPfreeBufferArrayNull(scip, &fixings2);
SCIPfreeBufferArrayNull(scip, &fixings1);
SCIPfreeBufferArrayNull(scip, &edgearray);
SCIPfreeBufferArrayNull(scip, &rowsmaxval);
SCIPfreeBufferArrayNull(scip, &varrank);
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;
}
