csintegerprogramming.cs

// 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.

using System;
using Google.OrTools.LinearSolver;

public class CsIntegerProgramming
{
  private static void RunIntegerProgrammingExample(String solverType)
  {
    Solver solver = Solver.CreateSolver("IntegerProgramming", solverType);
    if (solver == null)
    {
      Console.WriteLine("Could not create solver " + solverType);
      return;
    }
    // x1 and x2 are integer non-negative variables.
    Variable x1 = solver.MakeIntVar(0.0, double.PositiveInfinity, "x1");
    Variable x2 = solver.MakeIntVar(0.0, double.PositiveInfinity, "x2");

    // Minimize x1 + 2 * x2.
    Objective objective = solver.Objective();
    objective.SetMinimization();
    objective.SetCoefficient(x1, 1);
    objective.SetCoefficient(x2, 2);

    // 2 * x2 + 3 * x1 >= 17.
    Constraint ct = solver.MakeConstraint(17, double.PositiveInfinity);
    ct.SetCoefficient(x1, 3);
    ct.SetCoefficient(x2, 2);

    Solver.ResultStatus resultStatus = solver.Solve();

    // Check that the problem has an optimal solution.
    if (resultStatus != Solver.ResultStatus.OPTIMAL)
    {
      Console.WriteLine("The problem does not have an optimal solution!");
      return;
    }

    Console.WriteLine("Problem solved in " + solver.WallTime() +
                      " milliseconds");

    // The objective value of the solution.
    Console.WriteLine("Optimal objective value = " + objective.Value());

    // The value of each variable in the solution.
    Console.WriteLine("x1 = " + x1.SolutionValue());
    Console.WriteLine("x2 = " + x2.SolutionValue());

    Console.WriteLine("Advanced usage:");
    Console.WriteLine("Problem solved in " + solver.Nodes() +
                      " branch-and-bound nodes");
  }

  private static void RunIntegerProgrammingExampleNaturalApi(String solverType)
  {
    Solver solver = Solver.CreateSolver("IntegerProgramming", solverType);
    if (solver == null)
    {
      Console.WriteLine("Could not create solver " + solverType);
      return;
    }
    // x1 and x2 are integer non-negative variables.
    Variable x1 = solver.MakeIntVar(0.0, double.PositiveInfinity, "x1");
    Variable x2 = solver.MakeIntVar(0.0, double.PositiveInfinity, "x2");

    solver.Minimize(x1 + 2 * x2);
    solver.Add(2 * x2 + 3 * x1 >= 17);

    Solver.ResultStatus resultStatus = solver.Solve();

    // Check that the problem has an optimal solution.
    if (resultStatus != Solver.ResultStatus.OPTIMAL)
    {
      Console.WriteLine("The problem does not have an optimal solution!");
      return;
    }

    Console.WriteLine("Problem solved in " + solver.WallTime() +
                      " milliseconds");

    // The objective value of the solution.
    Console.WriteLine("Optimal objective value = " +
                      solver.Objective().Value());

    // The value of each variable in the solution.
    Console.WriteLine("x1 = " + x1.SolutionValue());
    Console.WriteLine("x2 = " + x2.SolutionValue());

    Console.WriteLine("Advanced usage:");
    Console.WriteLine("Problem solved in " + solver.Nodes() +
                      " branch-and-bound nodes");
  }

  static void Main()
  {
    Console.WriteLine("---- Integer programming example with GLPK ----");
    RunIntegerProgrammingExample("GLPK_MIXED_INTEGER_PROGRAMMING");
    Console.WriteLine("---- Linear programming example with CBC ----");
    RunIntegerProgrammingExample("CBC_MIXED_INTEGER_PROGRAMMING");
    Console.WriteLine("---- Linear programming example with SCIP ----");
    RunIntegerProgrammingExample("SCIP_MIXED_INTEGER_PROGRAMMING");
    Console.WriteLine(
        "---- Integer programming example (Natural API) with GLPK ----");
    RunIntegerProgrammingExampleNaturalApi("GLPK_MIXED_INTEGER_PROGRAMMING");
    Console.WriteLine(
        "---- Linear programming example (Natural API) with CBC ----");
    RunIntegerProgrammingExampleNaturalApi("CBC_MIXED_INTEGER_PROGRAMMING");
    Console.WriteLine(
        "---- Linear programming example (Natural API) with SCIP ----");
    RunIntegerProgrammingExampleNaturalApi("SCIP_MIXED_INTEGER_PROGRAMMING");
  }
}