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better MakeScalProdLessOrEqual

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lperron@google.com
2012-06-23 18:58:32 +00:00
parent fb08bb1e21
commit 675b2861b9
1 changed files with 95 additions and 0 deletions
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95
src/constraint_solver/expr_array.cc
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@@ -2441,6 +2441,101 @@ template<class T> Constraint* MakeScalProdLessOrEqualFct(Solver* solver,
coefficients,
upper_bound));
}
// Some simplications
int constants = 0;
int positives = 0;
int negatives = 0;
for (int i = 0; i < size; ++i) {
if (coefficients[i] == 0 || vars[i]->Bound()) {
constants++;
} else if (coefficients[i] > 0) {
positives++;
} else {
negatives++;
}
}
if (positives > 0 && negatives > 0) {
std::vector<IntVar*> pos_terms;
std::vector<IntVar*> neg_terms;
int64 rhs = upper_bound;
for (int i = 0; i < size; ++i) {
if (coefficients[i] == 0 || vars[i]->Bound()) {
rhs -= coefficients[i] * vars[i]->Min();
} else if (coefficients[i] > 0) {
pos_terms.push_back(solver->MakeProd(vars[i], coefficients[i])->Var());
} else {
neg_terms.push_back(solver->MakeProd(vars[i], -coefficients[i])->Var());
}
}
if (negatives == 1) {
IntVar* const neg_term = solver->MakeSum(neg_terms[0], rhs)->Var();
return solver->MakeLessOrEqual(
solver->MakeSum(pos_terms)->Var(), neg_term);
} else if (positives == 1) {
IntVar* const pos_term = solver->MakeSum(pos_terms[0], -rhs)->Var();
return solver->MakeGreaterOrEqual(
solver->MakeSum(neg_terms)->Var(), pos_term);
} else {
if (rhs != 0) {
neg_terms.push_back(solver->MakeIntConst(rhs));
}
return solver->MakeLessOrEqual(
solver->MakeSum(pos_terms)->Var(),
solver->MakeSum(neg_terms)->Var());
}
} else if (positives == 1) {
IntVar* pos_term = NULL;
int64 rhs = upper_bound;
for (int i = 0; i < size; ++i) {
if (coefficients[i] == 0 || vars[i]->Bound()) {
rhs -= coefficients[i] * vars[i]->Min();
} else if (coefficients[i] > 0) {
pos_term = solver->MakeProd(vars[i], coefficients[i])->Var();
} else {
LOG(FATAL) << "Should not be here";
}
}
return solver->MakeLessOrEqual(pos_term, rhs);
} else if (negatives == 1) {
IntVar* neg_term = NULL;
int64 rhs = upper_bound;
for (int i = 0; i < size; ++i) {
if (coefficients[i] == 0 || vars[i]->Bound()) {
rhs -= coefficients[i] * vars[i]->Min();
} else if (coefficients[i] > 0) {
LOG(FATAL) << "Should not be here";
} else {
neg_term = solver->MakeProd(vars[i], -coefficients[i])->Var();
}
}
return solver->MakeGreaterOrEqual(neg_term, -rhs);
} else if (positives > 1) {
std::vector<IntVar*> pos_terms;
int64 rhs = upper_bound;
for (int i = 0; i < size; ++i) {
if (coefficients[i] == 0 || vars[i]->Bound()) {
rhs -= coefficients[i] * vars[i]->Min();
} else if (coefficients[i] > 0) {
pos_terms.push_back(solver->MakeProd(vars[i], coefficients[i])->Var());
} else {
LOG(FATAL) << "Should not be here";
}
}
return solver->MakeSumLessOrEqual(pos_terms, rhs);
} else if (negatives > 1) {
std::vector<IntVar*> neg_terms;
int64 rhs = upper_bound;
for (int i = 0; i < size; ++i) {
if (coefficients[i] == 0 || vars[i]->Bound()) {
rhs -= coefficients[i] * vars[i]->Min();
} else if (coefficients[i] > 0) {
LOG(FATAL) << "Should not be here";
} else {
neg_terms.push_back(solver->MakeProd(vars[i], -coefficients[i])->Var());
}
}
return solver->MakeSumGreaterOrEqual(neg_terms, -rhs);
}
std::vector<IntVar*> terms;
for (int i = 0; i < size; ++i) {
terms.push_back(solver->MakeProd(vars[i], coefficients[i])->Var());