BranchPtr
MultilinearTermsHandler::doBranch_(BranchDirection UpOrDown, ConstVariablePtr v,
double bvalue)
{
BranchPtr branch;
BoundType lu;
VariableType vtype = v->getType();
#if defined(DEBUG_MULTILINEARTERMS_HANDLER)
std::cout << "Branching: " << (UpOrDown == DownBranch ? "Down" : "Up")
<< " at value: " << bvalue << " on: " << std::endl;
v->write(std::cout);
#endif
branch = (BranchPtr) new Branch();
double branching_value = bvalue;
// Change bounds on the x var (called v here)
if (UpOrDown == DownBranch) {
lu = Upper;
if (vtype != Continuous) branching_value = floor(bvalue);
}
else {
lu = Lower;
if (vtype != Continuous) branching_value = ceil(bvalue);
}
VarBoundModPtr vmod = (VarBoundModPtr) new VarBoundMod(v, lu, branching_value);
assert(!"check whether this needs to be addRMod instead");
branch->addPMod(vmod);
branch->setActivity(0.5);// TODO: set this correctly
return branch;
}
void KnapCovHandler::separate(ConstSolutionPtr sol, NodePtr,
RelaxationPtr rel, CutManager * cmanager,
SolutionPoolPtr , bool * ,
SeparationStatus * status)
{
// Check integer feasibility of sol, must add cuts if it is not integral.
numvars_ = minlp_->getNumVars();
VariableType type;
const double * x = sol->getPrimal();
// Is the relaxation solution is integer feasible.
bool isintfeas = true;
// Iterators for variables.
VariableConstIterator it;
VariableConstIterator begin = rel->varsBegin();
VariableConstIterator end = rel->varsEnd();
// Temporary variable holder.
ConstVariablePtr var;
// Value of variable.
double value;
bool separated = false;
UInt n_added = 0;
// Check if integrality is satisfied for each integer variable.
for (it=begin; it!=end; ++it) {
var = *it;
type = var->getType();
if (type==Binary || type==Integer) {
value = x[var->getIndex()];
if (fabs(value - floor(value + 0.5)) > intTol_) {
isintfeas = false;
break;
}
}
}
if (isintfeas == false) {
// We do another check in CoverCutGneerator for integrality, may be we
// should eliminate it and use the one above.
// Generate cover cuts from current relaxation.
CoverCutGeneratorPtr cover = (CoverCutGeneratorPtr) new CoverCutGenerator(rel,sol, env_);
// Add cuts to the relaxation by using cut manager.
CutVector violatedcuts = cover->getViolatedCutList();
CutIterator itc;
CutIterator beginc = violatedcuts.begin();
CutIterator endc = violatedcuts.end();
// Serdar I am not sure if we should add the constraints generated by
// addCuts to the constraint vector of knapsack cover handler.
// Currently CutMan2::addCuts does not add the cuts to the relaxation formulation.
cmanager->addCuts(beginc, endc);
cmanager->separate(rel, sol, &separated, &n_added);
if (n_added>0) {
*status = SepaResolve;
}
// Update statistics by using return from cover cut generator.
ConstCovCutGenStatsPtr covstats = cover->getStats();
// Later put the code below to updateStats function.
stats_->knaps += covstats->knaps;
stats_->cuts += covstats->cuts;
stats_->extended += covstats->extended;
stats_->simple += covstats->simple;
stats_->gns += covstats->gns;
stats_->singlectwo += covstats->singlectwo;
}
}