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enable multiple rounds of cuts at the root node

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This commit is contained in:
Laurent Perron
2020-03-02 17:26:45 +01:00
parent d956e29942
commit b2d959afe8
2 changed files with 13 additions and 6 deletions
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14
ortools/sat/linear_programming_constraint.cc
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@@ -1192,13 +1192,16 @@ bool LinearProgrammingConstraint::Propagate() {
if (!SolveLp()) return true;
// Add new constraints to the LP and resolve?
//
// TODO(user): We might want to do that more than once. Currently we rely on
// this beeing called again on the next IncrementalPropagate() call, but that
// might not always happen at level zero.
if (simplex_.GetProblemStatus() == glop::ProblemStatus::OPTIMAL) {
const int max_cuts_rounds =
trail_->CurrentDecisionLevel() == 0
? sat_parameters_.max_cut_rounds_at_level_zero()
: 1;
int cuts_round = 0;
while (simplex_.GetProblemStatus() == glop::ProblemStatus::OPTIMAL &&
cuts_round < max_cuts_rounds) {
// We wait for the first batch of problem constraints to be added before we
// begin to generate cuts.
cuts_round++;
if (!integer_lp_.empty() &&
constraint_manager_.num_cuts() < sat_parameters_.max_num_cuts()) {
// The "generic" cuts are currently part of this class as they are using
@@ -1238,6 +1241,7 @@ bool LinearProgrammingConstraint::Propagate() {
if (trail_->CurrentDecisionLevel() == 0) {
lp_at_level_zero_is_final_ = true;
}
break;
}
}

5
ortools/sat/sat_parameters.proto
View File

@@ -21,7 +21,7 @@ option java_multiple_files = true;
// Contains the definitions for all the sat algorithm parameters and their
// default values.
//
// NEXT TAG: 154
// NEXT TAG: 155
message SatParameters {
// ==========================================================================
// Branching and polarity
@@ -597,6 +597,9 @@ message SatParameters {
// feature.
optional double min_orthogonality_for_lp_constraints = 115 [default = 0.0];
// Max number of time we perform cut generation and resolve the LP at level 0.
optional int32 max_cut_rounds_at_level_zero = 154 [default = 1];
// If a constraint/cut in LP is not active for that many consecutive OPTIMAL
// solves, remove it from the LP. Note that it might be added again later if
// it become violated by the current LP solution.