volsay3.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 Volsay3 {
  /**
   * Volsay problem.
   *
   * From the OPL model volsay.mod.
   * This version use arrays and matrices
   *
   * Also see
   *  http://www.hakank.org/or-tools/volsay2.cs
   *  http://www.hakank.org/or-tools/volsay3.py
   */
  private static void Solve() {
    Solver solver = new Solver(
    	   "Volsay3", Solver.OptimizationProblemType.CLP_LINEAR_PROGRAMMING);

    int num_products = 2;
    IEnumerable<int> PRODUCTS = Enumerable.Range(0, num_products);
    String[] products = {"Gas", "Chloride"};
    String[] components = {"nitrogen", "hydrogen", "chlorine"};

    int[,] demand = { {1,3,0}, {1,4,1}};
    int[] profit = {30,40};
    int[] stock = {50,180,40};

    //
    // Variables
    //
    Variable[] production = new Variable[num_products];
    foreach(int p in PRODUCTS) {
      production[p] = solver.MakeNumVar(0, 100000, products[p]);
    }

    //
    // Constraints
    //
    int c_len = components.Length;
    Constraint[] cons = new Constraint[c_len];
    for(int c = 0; c < c_len; c++) {
      cons[c] = solver.Add( (from p in PRODUCTS
                             select (demand[p,c]*production[p])).
                            ToArray().Sum() <= stock[c]);
    }

    //
    // Objective
    //
    solver.Maximize( (from p in PRODUCTS
                      select (profit[p]*production[p])).
                     ToArray().Sum()
                    );

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

    Console.WriteLine("Objective: {0}", solver.Objective().Value());
    foreach(int p in PRODUCTS) {
      Console.WriteLine("{0,-10}: {1} ReducedCost: {2}",
                        products[p],
                        production[p].SolutionValue(),
                        production[p].ReducedCost());
    }

    double[] activities = solver.ComputeConstraintActivities();
    for(int c = 0; c < c_len; c++) {
      Console.WriteLine("Constraint {0} DualValue {1} Activity: {2} lb: {3} ub: {4}",
                        c,
                        cons[c].DualValue(),
                        activities[cons[c].Index()],
                        cons[c].Lb(),
                        cons[c].Ub());
    }

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

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