130 lines
3.5 KiB
C#
130 lines
3.5 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 Assignment {
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/**
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*
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* Assignment problem
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*
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* From Wayne Winston "Operations Research",
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* Assignment Problems, page 393f
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* (generalized version with added test column)
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*
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* See See http://www.hakank.org/or-tools/assignment.py
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*
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*/
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private static void Solve() {
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Solver solver = new Solver("Assignment");
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//
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// data
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//
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// Problem instance
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// hakank: I added the fifth column to make it more
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// interesting
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int rows = 4;
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int cols = 5;
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int[, ] cost = {
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{14, 5, 8, 7, 15}, {2, 12, 6, 5, 3}, {7, 8, 3, 9, 7}, {2, 4, 6, 10, 1}};
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//
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// Decision variables
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//
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IntVar[, ] x = solver.MakeBoolVarMatrix(rows, cols, "x");
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IntVar[] x_flat = x.Flatten();
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//
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// Constraints
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//
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// Exacly one assignment per row (task),
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// i.e. all rows must be assigned with one worker
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for (int i = 0; i < rows; i++) {
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solver.Add((from j in Enumerable.Range(0, cols) select x[i, j])
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.ToArray()
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.Sum() == 1);
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}
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// At most one assignments per column (worker)
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for (int j = 0; j < cols; j++) {
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solver.Add((from i in Enumerable.Range(0, rows) select x[i, j])
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.ToArray()
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.Sum() <= 1);
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}
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// Total cost
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IntVar total_cost =
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(from i in Enumerable.Range(0, rows) from j in Enumerable.Range(0, cols)
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select(cost[i, j] * x[i, j]))
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.ToArray()
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.Sum()
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.Var();
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//
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// objective
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//
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OptimizeVar objective = total_cost.Minimize(1);
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//
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// Search
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//
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DecisionBuilder db = solver.MakePhase(x_flat, Solver.INT_VAR_DEFAULT,
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Solver.INT_VALUE_DEFAULT);
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solver.NewSearch(db, objective);
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while (solver.NextSolution()) {
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Console.WriteLine("total_cost: {0}", total_cost.Value());
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for (int i = 0; i < rows; i++) {
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for (int j = 0; j < cols; j++) {
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Console.Write(x [i, j]
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.Value() +
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" ");
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}
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Console.WriteLine();
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}
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Console.WriteLine();
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Console.WriteLine("Assignments:");
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for (int i = 0; i < rows; i++) {
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Console.Write("Task " + i);
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for (int j = 0; j < cols; j++) {
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if (x [i, j]
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.Value() == 1) {
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Console.WriteLine(" is done by " + j);
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}
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}
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}
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Console.WriteLine();
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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) { Solve(); }
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}
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