always-cautious/ortools-clone
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

improve multi_knapsack_sat.cc

Browse Source
This commit is contained in:
Laurent Perron
2019-04-05 16:43:23 +02:00
parent 17b9b597a1
commit e685805fc8
1 changed files with 27 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
examples/cpp/multi_knapsack_sat.cc
View File

@@ -12,21 +12,22 @@
// limitations under the License.
// Solve a scaled constrained two dimensional knapsack problem.
// Each bin must be filled with items with min and max weights, and min and max volumes.
// As is a knapsack, the objective is to maximize total value.
// Each bin must be filled with items with min and max weights, and min and max
// volumes. As is a knapsack, the objective is to maximize total value. It turns
// out that the objective is to maximize weights.
//
// Data is for 1 bin and 10 items. Scaling is done my having m bins and m copies of each items.
// Data is for 1 bin and 10 items. Scaling is done my having m bins and m copies
// of each items.
#include <string>
#include <vector>
#include "absl/strings/str_format.h"
#include "ortools/base/commandlineflags.h"
#include "ortools/base/logging.h"
#include "ortools/sat/cp_model.h"
#include "ortools/sat/model.h"
#include "ortools/sat/sat_parameters.pb.h"
DEFINE_int32(size, 16, "scaling factor of the model");
DEFINE_string(params, "", "Sat paramters");
DEFINE_string(params, "", "Sat parameters");
namespace operations_research {
namespace sat {
@@ -36,10 +37,11 @@ static const int kWeightMax = 22000;
static const int kVolumeMin = 1156;
static const int kVolumeMax = 1600;
// data for a single bin problem
// Data for a single bin problem
static const int kItemsWeights[] = {1008, 2087, 5522, 5250, 5720,
4998, 275, 3145, 12580, 382};
static const int kItemsVolumes[] = {281, 307, 206, 111, 275, 79, 23, 65, 261, 40};
static const int kItemsVolumes[] = {281, 307, 206, 111, 275,
79, 23, 65, 261, 40};
static const int kNumItems = 10;
void MultiKnapsackSat(int scaling, const std::string& params) {
@@ -74,43 +76,41 @@ void MultiKnapsackSat(int scaling, const std::string& params) {
for (int b = 0; b < num_bins; ++b) {
IntVar bin_weight = builder.NewIntVar({kWeightMin, kWeightMax});
bin_weights.push_back(bin_weight);
builder.AddEquality(
LinearExpr::BooleanScalProd(items_in_bins[b], weights), bin_weight);
builder.AddEquality(LinearExpr::BooleanScalProd(items_in_bins[b], weights),
bin_weight);
builder.AddLinearConstraint(
LinearExpr::BooleanScalProd(items_in_bins[b], volumes),
{kVolumeMin, kVolumeMax});
}
// Each is selected at most one time.
// Each item is selected at most one time.
for (int i = 0; i < num_items; ++i) {
std::vector<BoolVar> copies(num_bins);
std::vector<BoolVar> bin_contain_item(num_bins);
for (int b = 0; b < num_bins; ++b) {
copies[b] = items_in_bins[b][i];
bin_contain_item[b] = items_in_bins[b][i];
}
builder.AddEquality(LinearExpr::BooleanSum(copies), selected_items[i]);
builder.AddEquality(LinearExpr::BooleanSum(bin_contain_item),
selected_items[i]);
}
// Symmetry breaking. Weights are decreasing accross bins.
// for (int b = 0; b + 1 < num_bins; ++b) {
// builder.AddGreaterOrEqual(bin_weights[b], bin_weights[b + 1]);
// }
// Maximize value.
// Maximize the sums of weights.
builder.Maximize(LinearExpr::Sum(bin_weights));
// And solve.
Model model;
if (!params.empty()) {
model.Add(NewSatParameters(params));
}
const CpSolverResponse response = SolveWithModel(builder.Build(), &model);
SatParameters sat_parameters;
sat_parameters.set_log_search_progress(true);
sat_parameters.MergeFromString(params);
const CpSolverResponse response =
SolveWithParameters(builder.Build(), params);
LOG(INFO) << CpSolverResponseStats(response);
}
} // namespace sat
} // namespace operations_research
int main(int argc, char **argv) {
int main(int argc, char** argv) {
google::InitGoogleLogging(argv[0]);
absl::SetFlag(&FLAGS_logtostderr, true);
gflags::ParseCommandLineFlags(&argc, &argv, true);
operations_research::sat::MultiKnapsackSat(FLAGS_size, FLAGS_params);
return EXIT_SUCCESS;