133 lines
3.8 KiB
C#
133 lines
3.8 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.Linq;
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using System.Text.RegularExpressions;
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using Google.OrTools.ConstraintSolver;
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public class SetCoveringDeployment
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{
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/**
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*
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* Solves a set covering deployment problem.
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* See See http://www.hakank.org/or-tools/set_covering_deployment.py
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*
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*/
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private static void Solve()
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{
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Solver solver = new Solver("SetCoveringDeployment");
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//
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// data
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//
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// From http://mathworld.wolfram.com/SetCoveringDeployment.html
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string[] countries = { "Alexandria", "Asia Minor", "Britain", "Byzantium", "Gaul", "Iberia", "Rome", "Tunis" };
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int n = countries.Length;
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// the incidence matrix (neighbours)
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int[,] mat = { { 0, 1, 0, 1, 0, 0, 1, 1 }, { 1, 0, 0, 1, 0, 0, 0, 0 }, { 0, 0, 0, 0, 1, 1, 0, 0 },
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{ 1, 1, 0, 0, 0, 0, 1, 0 }, { 0, 0, 1, 0, 0, 1, 1, 0 }, { 0, 0, 1, 0, 1, 0, 1, 1 },
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{ 1, 0, 0, 1, 1, 1, 0, 1 }, { 1, 0, 0, 0, 0, 1, 1, 0 } };
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//
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// Decision variables
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//
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// First army
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IntVar[] x = solver.MakeIntVarArray(n, 0, 1, "x");
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// Second (reserve) army
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IntVar[] y = solver.MakeIntVarArray(n, 0, 1, "y");
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// total number of armies
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IntVar num_armies = (x.Sum() + y.Sum()).Var();
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//
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// Constraints
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//
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//
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// Constraint 1: There is always an army in a city
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// (+ maybe a backup)
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// Or rather: Is there a backup, there
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// must be an an army
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//
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for (int i = 0; i < n; i++)
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{
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solver.Add(x[i] >= y[i]);
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}
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//
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// Constraint 2: There should always be an backup
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// army near every city
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//
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for (int i = 0; i < n; i++)
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{
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IntVar[] count_neighbours =
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(from j in Enumerable.Range(0, n) where mat[i, j] == 1 select(y[j]))
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.ToArray();
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solver.Add((x[i] + count_neighbours.Sum()) >= 1);
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}
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//
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// objective
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//
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OptimizeVar objective = num_armies.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("num_armies: " + num_armies.Value());
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for (int i = 0; i < n; i++)
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{
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if (x[i].Value() == 1)
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{
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Console.Write("Army: " + countries[i] + " ");
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}
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if (y[i].Value() == 1)
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{
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Console.WriteLine(" Reverse army: " + countries[i]);
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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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Solve();
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}
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}
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