130 lines
3.3 KiB
Java
130 lines
3.3 KiB
Java
// Copyright 2011 Hakan Kjellerstrand hakank@gmail.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.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 SetCovering2 {
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static {
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System.loadLibrary("jniortools");
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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_covering2.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("SetCovering2");
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//
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// data
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//
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// Example 9.1-2 from
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// Taha "Operations Research - An Introduction",
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// page 354ff.
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// Minimize the number of security telephones in street
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// corners on a campus.
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int n = 8; // maximum number of corners
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int num_streets = 11; // number of connected streets
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// corners of each street
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// Note: 1-based (handled below)
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int[][] corner = {{1,2},
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{2,3},
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{4,5},
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{7,8},
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{6,7},
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{2,6},
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{1,6},
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{4,7},
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{2,4},
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{5,8},
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{3,5}};
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//
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// variables
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//
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IntVar[] x = solver.makeIntVarArray(n, 0, 1, "x");
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// number of telephones, 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 all cities are covered
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for(int i = 0; i < num_streets; i++) {
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IntVar[] b = new IntVar[2];
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b[0] = x[corner[i][0] - 1];
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b[1] = x[corner[i][1] - 1];
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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 i = 0; i < n; i++) {
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System.out.print(x[i].value() + " ");
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}
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System.out.println();
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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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SetCovering2.solve();
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}
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}
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