volsay.cs

// Copyright 2012 Hakan Kjellerstrand
//
// 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 System.Collections;
using System.Collections.Generic;
using System.Linq;
using Google.OrTools.LinearSolver;

public class Volsay {
  /**
   * Volsay problem.
   *
   * From the OPL model volsay.mod.
   *
   * Also see http://www.hakank.org/or-tools/volsay.py
   */
  private static void Solve() {
    Solver solver = new Solver(
    	   "Volsay", Solver.OptimizationProblemType.CLP_LINEAR_PROGRAMMING);

    //
    // Variables
    //
    Variable Gas = solver.MakeNumVar(0, 100000, "Gas");
    Variable Chloride = solver.MakeNumVar(0, 100000, "Cloride");

    Constraint c1 = solver.Add(Gas + Chloride <= 50);
    Constraint c2 = solver.Add(3 * Gas + 4 * Chloride <= 180);

    solver.Maximize(40 * Gas + 50 * Chloride);

    Solver.ResultStatus resultStatus = solver.Solve();

    if (resultStatus != Solver.ResultStatus.OPTIMAL) {
      Console.WriteLine("The problem don't have an optimal solution.");
      return;
    }

    Console.WriteLine("Objective: {0}", solver.Objective().Value());

    Console.WriteLine("Gas      : {0} ReducedCost: {1}",
                      Gas.SolutionValue(),
                      Gas.ReducedCost());

    Console.WriteLine("Chloride : {0} ReducedCost: {1}",
                      Chloride.SolutionValue(),
                      Chloride.ReducedCost());

    double[] activities = solver.ComputeConstraintActivities();
    Console.WriteLine("c1       : DualValue: {0} Activity: {1}",
                      c1.DualValue(),
                      activities[c1.Index()]);

    Console.WriteLine("c2       : DualValue: {0} Activity: {1}",
                      c2.DualValue(),
                      activities[c2.Index()]);

    Console.WriteLine("\nWallTime: " + solver.WallTime());
    Console.WriteLine("Iterations: " + solver.Iterations());
  }

  public static void Main(String[] args) {
    Solve();
  }
}