ortools-clone/examples/cpp/integer_programming.cc

// Copyright 2010-2018 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Integer programming example that shows how to use the API.

#include "ortools/base/logging.h"
#include "ortools/linear_solver/linear_solver.h"

namespace operations_research {
  void RunIntegerProgrammingExample(
      MPSolver::OptimizationProblemType optimization_problem_type) {
    MPSolver solver("IntegerProgrammingExample", optimization_problem_type);
    const double infinity = solver.infinity();
    // x and y are integer non-negative variables.
    MPVariable* const x = solver.MakeIntVar(0.0, infinity, "x");
    MPVariable* const y = solver.MakeIntVar(0.0, infinity, "y");

    // Maximize x + 10 * y.
    MPObjective* const objective = solver.MutableObjective();
    objective->SetCoefficient(x, 1);
    objective->SetCoefficient(y, 10);
    objective->SetMaximization();

    // x + 7 * y <= 17.5.
    MPConstraint* const c0 = solver.MakeRowConstraint(-infinity, 17.5);
    c0->SetCoefficient(x, 1);
    c0->SetCoefficient(y, 7);

    // x <= 3.5
    MPConstraint* const c1 = solver.MakeRowConstraint(-infinity, 3.5);
    c1->SetCoefficient(x, 1);
    c1->SetCoefficient(y, 0);

    LOG(INFO) << "Number of variables = " << solver.NumVariables();
    LOG(INFO) << "Number of constraints = " << solver.NumConstraints();

    const MPSolver::ResultStatus result_status = solver.Solve();
    // Check that the problem has an optimal solution.
    if (result_status != MPSolver::OPTIMAL) {
      LOG(FATAL) << "The problem does not have an optimal solution!";
    }
    LOG(INFO) << "Solution:";
    LOG(INFO) << "x = " << x->solution_value();
    LOG(INFO) << "y = " << y->solution_value();
    LOG(INFO) << "Optimal objective value = " << objective->Value();
    LOG(INFO) << "";
    LOG(INFO) << "Advanced usage:";
    LOG(INFO) << "Problem solved in " << solver.wall_time() << " milliseconds";
    LOG(INFO) << "Problem solved in " << solver.iterations() << " iterations";
    LOG(INFO) << "Problem solved in " << solver.nodes() << " branch-and-bound nodes";
  }

  void RunAllExamples() {
#if defined(USE_CBC)
    LOG(INFO) << "---- Integer programming example with CBC ----";
    RunIntegerProgrammingExample(MPSolver::CBC_MIXED_INTEGER_PROGRAMMING);
#endif
#if defined(USE_GLPK)
    LOG(INFO) << "---- Integer programming example with GLPK ----";
    RunIntegerProgrammingExample(MPSolver::GLPK_MIXED_INTEGER_PROGRAMMING);
#endif
#if defined(USE_SCIP)
    LOG(INFO) << "---- Integer programming example with SCIP ----";
    RunIntegerProgrammingExample(MPSolver::SCIP_MIXED_INTEGER_PROGRAMMING);
#endif
#if defined(USE_GUROBI)
    LOG(INFO) << "---- Integer programming example with Gurobi ----";
    RunIntegerProgrammingExample(MPSolver::GUROBI_MIXED_INTEGER_PROGRAMMING);
#endif  // USE_GUROBI
#if defined(USE_CPLEX)
    LOG(INFO) << "---- Integer programming example with CPLEX ----";
    RunIntegerProgrammingExample(MPSolver::CPLEX_MIXED_INTEGER_PROGRAMMING);
#endif  // USE_CPLEX
  }
}  // namespace operations_research

int main(int argc, char** argv) {
  google::InitGoogleLogging(argv[0]);
  FLAGS_logtostderr = 1;
  operations_research::RunAllExamples();
  return EXIT_SUCCESS;
}