assignment.cs 3.46 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 24 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 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137
//
// 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.IO;
using System.Linq;
using System.Text.RegularExpressions;
using Google.OrTools.ConstraintSolver;

public class Assignment
{

  /**
   *
   * Assignment problem
   *
   * From Wayne Winston "Operations Research",
   * Assignment Problems, page 393f
   * (generalized version with added test column)
   *
   * See  See http://www.hakank.org/or-tools/assignment.py
   *
   */
  private static void Solve()
  {

    Solver solver = new Solver("Assignment");

    //
    // data
    //

    // Problem instance
    // hakank: I added the fifth column to make it more
    //         interesting
    int rows = 4;
    int cols = 5;
    int[,] cost = {
      {14,  5, 8,  7,  15},
      { 2, 12, 6,  5,   3},
      { 7,  8, 3,  9,   7},
      { 2,  4, 6, 10,   1}
    };


    //
    // Decision variables
    //
    IntVar[,] x = solver.MakeBoolVarMatrix(rows, cols, "x");
    IntVar[] x_flat = x.Flatten();

    //
    // Constraints
    //

    // Exacly one assignment per row (task),
    // i.e. all rows must be assigned with one worker
    for(int i = 0; i < rows; i++) {
      solver.Add((from j in Enumerable.Range(0, cols)
                  select x[i,j]).ToArray().Sum() == 1);
    }

    // At most one assignments per column (worker)
    for(int j = 0; j < cols; j++) {
      solver.Add((from i in Enumerable.Range(0, rows)
                  select x[i,j]).ToArray().Sum() <= 1);
    }

    // Total cost
    IntVar total_cost = (from i in Enumerable.Range(0, rows)
                         from j in Enumerable.Range(0, cols)
                         select (cost[i,j] * x[i,j])).ToArray().Sum().Var();

    //
    // objective
    //
    OptimizeVar objective = total_cost.Minimize(1);


    //
    // Search
    //
    DecisionBuilder db = solver.MakePhase(x_flat,
                                          Solver.INT_VAR_DEFAULT,
                                          Solver.INT_VALUE_DEFAULT);

    solver.NewSearch(db, objective);

    while (solver.NextSolution()) {
      Console.WriteLine("total_cost: {0}", total_cost.Value());
      for(int i = 0; i < rows; i++) {
        for(int j = 0; j < cols; j++) {
          Console.Write(x[i,j].Value() + " ");
        }
        Console.WriteLine();
      }
      Console.WriteLine();
      Console.WriteLine("Assignments:");
      for(int i = 0; i < rows; i++) {
        Console.Write("Task " + i);
        for(int j = 0; j < cols; j++) {
          if (x[i,j].Value() == 1) {
            Console.WriteLine(" is done by " + j);
          }
        }
      }
      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();
  }
}