134 lines
4.0 KiB
C#
134 lines
4.0 KiB
C#
//
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// Copyright 2012 Hakan Kjellerstrand
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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using System;
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using System.Collections;
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using System.IO;
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using System.Text.RegularExpressions;
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using Google.OrTools.ConstraintSolver;
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public class SetCovering4
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{
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/**
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*
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* Solves a set covering problem.
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* See See http://www.hakank.org/or-tools/set_covering4.py
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*
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*/
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private static void Solve(int set_partition)
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{
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Solver solver = new Solver("SetCovering4");
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//
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// data
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//
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// Set partition and set covering problem from
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// Example from the Swedish book
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// Lundgren, Roennqvist, Vaebrand
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// 'Optimeringslaera' (translation: 'Optimization theory'),
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// page 408.
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int num_alternatives = 10;
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int num_objects = 8;
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// costs for the alternatives
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int[] costs = { 19, 16, 18, 13, 15, 19, 15, 17, 16, 15 };
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// the alternatives, and their objects
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int[,] a = { // 1 2 3 4 5 6 7 8 the objects
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{ 1, 0, 0, 0, 0, 1, 0, 0 }, // alternative 1
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{ 0, 1, 0, 0, 0, 1, 0, 1 }, // alternative 2
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{ 1, 0, 0, 1, 0, 0, 1, 0 }, // alternative 3
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{ 0, 1, 1, 0, 1, 0, 0, 0 }, // alternative 4
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{ 0, 1, 0, 0, 1, 0, 0, 0 }, // alternative 5
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{ 0, 1, 1, 0, 0, 0, 0, 0 }, // alternative 6
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{ 0, 1, 1, 1, 0, 0, 0, 0 }, // alternative 7
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{ 0, 0, 0, 1, 1, 0, 0, 1 }, // alternative 8
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{ 0, 0, 1, 0, 0, 1, 0, 1 }, // alternative 9
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{ 1, 0, 0, 0, 0, 1, 1, 0 }
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}; // alternative 10
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//
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// Decision variables
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//
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IntVar[] x = solver.MakeIntVarArray(num_alternatives, 0, 1, "x");
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// number of assigned senators, to be minimized
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IntVar z = x.ScalProd(costs).VarWithName("z");
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//
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// Constraints
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//
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for (int j = 0; j < num_objects; j++)
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{
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IntVar[] b = new IntVar[num_alternatives];
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for (int i = 0; i < num_alternatives; i++)
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{
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b[i] = (x[i] * a[i, j]).Var();
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}
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if (set_partition == 1)
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{
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solver.Add(b.Sum() >= 1);
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}
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else
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{
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solver.Add(b.Sum() == 1);
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}
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}
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//
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// objective
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//
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OptimizeVar objective = z.Minimize(1);
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//
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// Search
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//
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DecisionBuilder db = solver.MakePhase(x, Solver.INT_VAR_DEFAULT, Solver.INT_VALUE_DEFAULT);
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solver.NewSearch(db, objective);
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while (solver.NextSolution())
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{
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Console.WriteLine("z: " + z.Value());
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Console.Write("Selected alternatives: ");
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for (int i = 0; i < num_alternatives; i++)
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{
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if (x[i].Value() == 1)
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{
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Console.Write((i + 1) + " ");
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}
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}
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Console.WriteLine("\n");
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}
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Console.WriteLine("\nSolutions: {0}", solver.Solutions());
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Console.WriteLine("WallTime: {0}ms", solver.WallTime());
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Console.WriteLine("Failures: {0}", solver.Failures());
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Console.WriteLine("Branches: {0} ", solver.Branches());
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solver.EndSearch();
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}
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public static void Main(String[] args)
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{
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Console.WriteLine("Set partition:");
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Solve(1);
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Console.WriteLine("\nSet covering:");
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Solve(0);
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}
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}
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