integer_programming_example.cc 3.13 KB
Newer Older
Valentin Platzgummer's avatar
Valentin Platzgummer committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
// 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.

// [START program]
// [START import]
#include <iostream>
#include "ortools/linear_solver/linear_solver.h"
// [END import]

namespace operations_research {
void IntegerProgrammingExample() {
  // [START solver]
  // Create the mip solver with the CBC backend.
24
  MPSolver solver("integer_programming_example",
Valentin Platzgummer's avatar
Valentin Platzgummer committed
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91
                  MPSolver::CBC_MIXED_INTEGER_PROGRAMMING);
  // [END solver]

  // [START variables]
  // x, y, and z are non-negative integer variables.
  MPVariable* const x = solver.MakeIntVar(0.0, solver.infinity(), "x");
  MPVariable* const y = solver.MakeIntVar(0.0, solver.infinity(), "y");
  MPVariable* const z = solver.MakeIntVar(0.0, solver.infinity(), "z");
  LOG(INFO) << "Number of variables = " << solver.NumVariables();
  // [END variables]

  // [START constraints]
  // 2*x + 7*y + 3*z <= 50
  MPConstraint* const constraint0 =
      solver.MakeRowConstraint(-solver.infinity(), 50);
  constraint0->SetCoefficient(x, 2);
  constraint0->SetCoefficient(y, 7);
  constraint0->SetCoefficient(z, 3);

  // 3*x - 5*y + 7*z <= 45
  MPConstraint* const constraint1 =
      solver.MakeRowConstraint(-solver.infinity(), 45);
  constraint1->SetCoefficient(x, 3);
  constraint1->SetCoefficient(y, -5);
  constraint1->SetCoefficient(z, 7);

  // 5*x + 2*y - 6*z <= 37
  MPConstraint* const constraint2 =
      solver.MakeRowConstraint(-solver.infinity(), 37);
  constraint2->SetCoefficient(x, 5);
  constraint2->SetCoefficient(y, 2);
  constraint2->SetCoefficient(z, -6);
  LOG(INFO) << "Number of constraints = " << solver.NumConstraints();
  // [END constraints]

  // [START objective]
  // Maximize 2*x + 2*y + 3*z
  MPObjective* const objective = solver.MutableObjective();
  objective->SetCoefficient(x, 2);
  objective->SetCoefficient(y, 2);
  objective->SetCoefficient(z, 3);
  objective->SetMaximization();
  // [END objective]

  // [START solve]
  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!";
  }
  // [END solve]

  // [START print_solution]
  LOG(INFO) << "Solution:";
  LOG(INFO) << "Optimal objective value = " << objective->Value();
  LOG(INFO) << x->name() << " = " << x->solution_value();
  LOG(INFO) << y->name() << " = " << y->solution_value();
  LOG(INFO) << z->name() << " = " << z->solution_value();
  // [END print_solution]
}
}  // namespace operations_research

int main(int argc, char** argv) {
  operations_research::IntegerProgrammingExample();
  return EXIT_SUCCESS;
}
// [END program]