scheduling_speakers.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.IO;
using System.Linq;
using System.Text.RegularExpressions;
using Google.OrTools.ConstraintSolver;


public class SchedulingSpeakers
{

  /**
   *
   * Scheduling speakers problem
   *
   *  From Rina Dechter, Constraint Processing, page 72
   *  Scheduling of 6 speakers in 6 slots.
   *
   * See http://www.hakank.org/google_or_tools/scheduling_speakers.py
   *
   */
  private static void Solve()
  {
    Solver solver = new Solver("SchedulingSpeakers");


    // number of speakers
    int n = 6;

    // slots available to speak
    int[][] available = {
                    // Reasoning:
      new int[] {3,4,5,6},    // 2) the only one with 6 after speaker F -> 1
      new int[] {3,4},        // 5) 3 or 4
      new int[] {2,3,4,5},    // 3) only with 5 after F -> 1 and A -> 6
      new int[] {2,3,4},      // 4) only with 2 after C -> 5 and F -> 1
      new int[] {3,4},        // 5) 3 or 4
      new int[] {1,2,3,4,5,6} // 1) the only with 1
    };


    //
    // Decision variables
    //
    IntVar[] x =  solver.MakeIntVarArray(n, 1, n, "x");

    //
    // Constraints
    //
    solver.Add(x.AllDifferent());

    for(int i = 0; i < n; i++) {
      solver.Add(x[i].Member(available[i]));
    }


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

    solver.NewSearch(db);

    while (solver.NextSolution()) {
      Console.WriteLine(string.Join(",", (from i in x select i.Value())));
    }

    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();
  }
}