141 lines
3.9 KiB
Java
141 lines
3.9 KiB
Java
// Copyright 2011 Hakan Kjellerstrand hakank@bonetmail.com
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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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package com.google.ortools.constraintsolver.samples;
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import java.io.*;
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import java.util.*;
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import java.text.*;
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import com.google.ortools.constraintsolver.DecisionBuilder;
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import com.google.ortools.constraintsolver.IntVar;
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import com.google.ortools.constraintsolver.Solver;
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import com.google.ortools.constraintsolver.OptimizeVar;
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public class SetCovering3 {
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static {
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System.loadLibrary("jniconstraintsolver");
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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 http://www.hakank.org/google_or_tools/set_covering3.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("SetCovering3");
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//
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// data
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//
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// Set covering problem from
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// Katta G. Murty: 'Optimization Models for Decision Making',
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// page 302f
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// http://ioe.engin.umich.edu/people/fac/books/murty/opti_model/junior-7.pdf
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int num_groups = 6;
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int num_senators = 10;
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// which group does a senator belong to?
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int[][] belongs = {{1, 1, 1, 1, 1, 0, 0, 0, 0, 0}, // 1 southern
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{0, 0, 0, 0, 0, 1, 1, 1, 1, 1}, // 2 northern
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{0, 1, 1, 0, 0, 0, 0, 1, 1, 1}, // 3 liberals
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{1, 0, 0, 0, 1, 1, 1, 0, 0, 0}, // 4 conservative
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{0, 0, 1, 1, 1, 1, 1, 0, 1, 0}, // 5 democrats
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{1, 1, 0, 0, 0, 0, 0, 1, 0, 1}}; // 6 republicans
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//
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// variables
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//
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IntVar[] x = solver.makeIntVarArray(num_senators, 0, 1, "x");
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// number of assigned senators, to be minimize
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IntVar z = solver.makeSum(x).var();
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//
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// constraints
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//
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// ensure that each group is covered by at least
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// one senator
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for(int i = 0; i < num_groups; i++) {
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IntVar[] b = new IntVar[num_senators];
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for(int j = 0; j < num_senators; j++) {
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b[j] = solver.makeProd(x[j], belongs[i][j]).var();
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}
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solver.addConstraint(
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solver.makeSumGreaterOrEqual(b, 1));
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}
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//
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// objective
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//
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OptimizeVar objective = solver.makeMinimize(z, 1);
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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.INT_VAR_DEFAULT,
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solver.INT_VALUE_DEFAULT);
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solver.newSearch(db, objective);
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//
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// output
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//
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while (solver.nextSolution()) {
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System.out.println("z: " + z.value());
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System.out.print("x: ");
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for(int j = 0; j < num_senators; j++) {
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System.out.print(x[j].value() + " ");
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}
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System.out.println();
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// More details
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for(int j = 0; j < num_senators; j++) {
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if (x[j].value() == 1) {
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System.out.print("Senator " + (1 + j) +
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" belongs to these groups: ");
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for(int i = 0; i < num_groups; i++) {
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if (belongs[i][j] == 1) {
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System.out.print((1 + i) + " ");
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}
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}
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System.out.println();
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}
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}
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}
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solver.endSearch();
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// Statistics
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System.out.println();
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System.out.println("Solutions: " + solver.solutions());
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System.out.println("Failures: " + solver.failures());
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System.out.println("Branches: " + solver.branches());
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System.out.println("Wall time: " + solver.wallTime() + "ms");
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}
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public static void main(String[] args) throws Exception {
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SetCovering3.solve();
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}
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}
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