149 lines
4.0 KiB
C#
149 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.Linq;
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using System.Text.RegularExpressions;
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using Google.OrTools.ConstraintSolver;
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public class PostOfficeProblem2
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{
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/**
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*
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* Post office problem.
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*
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* Problem statement:
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* http://www-128.ibm.com/developerworks/linux/library/l-glpk2/
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*
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* From Winston 'Operations Research: Applications and Algorithms':
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* """
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* A post office requires a different number of full-time employees working
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* on different days of the week [summarized below]. Union rules state that
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* each full-time employee must work for 5 consecutive days and then receive
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* two days off. For example, an employee who works on Monday to Friday
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* must be off on Saturday and Sunday. The post office wants to meet its
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* daily requirements using only full-time employees. Minimize the number
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* of employees that must be hired.
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*
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* To summarize the important information about the problem:
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*
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* Every full-time worker works for 5 consecutive days and takes 2 days off
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* - Day 1 (Monday): 17 workers needed
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* - Day 2 : 13 workers needed
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* - Day 3 : 15 workers needed
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* - Day 4 : 19 workers needed
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* - Day 5 : 14 workers needed
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* - Day 6 : 16 workers needed
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* - Day 7 (Sunday) : 11 workers needed
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*
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* The post office needs to minimize the number of employees it needs
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* to hire to meet its demand.
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* """
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*
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* Also see http://www.hakank.org/or-tools/post_office_problem2.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("PostOfficeProblem2");
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//
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// Data
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//
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// days 0..6, monday 0
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int n = 7;
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int[] need = {17, 13, 15, 19, 14, 16, 11};
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// Total cost for the 5 day schedule.
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// Base cost per day is 100.
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// Working saturday is 100 extra
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// Working sunday is 200 extra.
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int[] cost = {500, 600, 800, 800, 800, 800, 700};
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//
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// Decision variables
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//
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// No. of workers starting at day i
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IntVar[] x = solver.MakeIntVarArray(n, 0, 100, "x");
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IntVar total_cost = x.ScalProd(cost).Var();
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IntVar num_workers = x.Sum().Var();
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//
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// Constraints
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//
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for(int i = 0; i < n; i++) {
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IntVar s = (from j in Enumerable.Range(0, n)
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where j != (i+5) % n && j != (i+6) % n
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select x[j]).ToArray().Sum().Var();
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solver.Add(s >= need[i]);
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}
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// Add a limit for the cost
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solver.Add(total_cost <= 20000);
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//
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// objective
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//
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//
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OptimizeVar obj = total_cost.Minimize(100);
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//
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// Search
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//
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DecisionBuilder db = solver.MakePhase(x,
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Solver.CHOOSE_MIN_SIZE_LOWEST_MIN,
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Solver.ASSIGN_MIN_VALUE);
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solver.NewSearch(db, obj);
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while (solver.NextSolution()) {
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Console.WriteLine("num_workers: {0}", num_workers.Value());
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Console.WriteLine("total_cost: {0}", total_cost.Value());
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Console.Write("x: ");
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for(int i = 0; i < n; i++) {
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Console.Write(x[i].Value() + " ");
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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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