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small improvement on automatic restart

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This commit is contained in:
lperron@google.com
2011-01-28 15:26:52 +00:00
parent a4c5bb35dd
commit 9ec1ad2ace
2 changed files with 16 additions and 6 deletions
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11
constraint_solver/constraint_solver.h
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@@ -227,10 +227,15 @@ struct DefaultPhaseParameters {
// Seed used to initialize the random part in some heuristics.
int random_seed;
// Automatic Restart Size. When diving down, the size of the search
// space disminishes. If the current log of the search space is
// greater than the the minimal value encountered +
// space disminishes. We maintain the minimal log of the size of the search
// space with the following behavior:
// - A failure is ignored (no null size).
// - A solution has a size of 1 (and a log of 0).
// Then when backtracking, if the current log of the size of the
// search space is greater than the minimizal log size recorded +
// 'restart_log_size', then the search is restarted from scratch. A
// parameter < 0 means no restart.
// parameter < 0 means no restart. A parameter of 0 indicates that
// we restart after each failure.
double restart_log_size;
};

11
constraint_solver/default_search.cc
View File

@@ -516,7 +516,7 @@ class ImpactDecisionBuilder : public DecisionBuilder {
runner_(NewPermanentCallback(this,
&ImpactDecisionBuilder::RunHeuristics)),
heuristic_branch_count_(0),
min_log_search_space_(std::numeric_limits<double>::max()) {
min_log_search_space_(std::numeric_limits<double>::infinity()) {
CHECK_GE(size_, 0);
if (size_ > 0) {
vars_.reset(new IntVar*[size_]);
@@ -663,7 +663,7 @@ class ImpactDecisionBuilder : public DecisionBuilder {
virtual Decision* Next(Solver* const solver) {
if (!init_done_) {
LOG(INFO) << "Init impact based search phase on " << size_
LOG(INFO) << "Init impact based search phase on " << size_
<< " variables, initialization splits = "
<< parameters_.initialization_splits
<< ", heuristic_period = " << parameters_.heuristic_period
@@ -701,7 +701,7 @@ class ImpactDecisionBuilder : public DecisionBuilder {
} else if (min_log_search_space_ + parameters_.restart_log_size
< log_search_space_size) {
VLOG(2) << "Restarting ";
min_log_search_space_ = std::numeric_limits<double>::max();
min_log_search_space_ = std::numeric_limits<double>::infinity();
solver->RestartSearch();
}
}
@@ -735,8 +735,13 @@ class ImpactDecisionBuilder : public DecisionBuilder {
name(heuristic_name),
runs(heuristic_runs) {}
// The decision builder we are going to use in this dive.
DecisionBuilder* const phase;
// A name for logging purposes.
const string name;
// How many time we will run this particular heuristic in case the
// parameter run_all_heuristics is true. This is useful for random
// heuristics where it makes sense to run them more than once.
const int runs;
};