csdiet.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 Google.OrTools.ConstraintSolver;

public class Diet
{
  /**
   *
   * Solves the Diet problem
   *
   * See http://www.hakank.org/google_or_tools/diet1.py
   *
   */
  private static void Solve()
  {
    Solver solver = new Solver("Diet");

    int n = 4;
    int[] price  = { 50, 20, 30, 80}; // in cents

    // requirements for each nutrition type
    int[] limits = {500,  6, 10,  8}; 
    string[] products = {"A", "B", "C", "D"};

    // nutritions for each product
    int[] calories  = {400, 200, 150, 500};
    int[] chocolate = {3, 2, 0, 0};
    int[] sugar     = {2, 2, 4, 4};
    int[] fat       = {2, 4, 1, 5};



    //
    // Decision variables
    //
    IntVar[] x = solver.MakeIntVarArray(n, 0, 100, "x");
    IntVar cost = x.ScalProd(price).Var();



    //
    // Constraints
    //
    
    // solver.Add(solver.MakeScalProdGreaterOrEqual(x, calories,  limits[0]));
    solver.Add(x.ScalProd(calories)  >= limits[0]);
    solver.Add(x.ScalProd(chocolate) >= limits[1]);
    solver.Add(x.ScalProd(sugar)     >= limits[2]);
    solver.Add(x.ScalProd(fat)       >= limits[3]);

    // 
    // Objective
    //
    OptimizeVar obj = cost.Minimize(1);

    //
    // Search
    //
    DecisionBuilder db = solver.MakePhase(x,
                                          Solver.CHOOSE_PATH,
                                          Solver.ASSIGN_MIN_VALUE);

    solver.NewSearch(db, obj);
    while (solver.NextSolution()) {
      Console.WriteLine("cost: {0}", cost.Value());
      Console.WriteLine("Products: ");
      for(int i = 0; i < n; i++) {
        Console.WriteLine("{0}: {1}", products[i], x[i].Value());
      }
      
      Console.WriteLine();
    }

    Console.WriteLine("\nSolutions: {0}", solver.Solutions());
    Console.WriteLine("WallTime: {0}ms", solver.WallTime());
    Console.WriteLine("Failures: {0}", solver.Failures());
    Console.WriteLine("Branches: {0} ", solver.Branches());

    solver.EndSearch();

  }

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