142 lines
3.9 KiB
Java
142 lines
3.9 KiB
Java
// Copyright 2011 Hakan Kjellerstrand hakank@gmail.com
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
import java.io.*;
|
|
import java.util.*;
|
|
import java.text.*;
|
|
|
|
import com.google.ortools.constraintsolver.DecisionBuilder;
|
|
import com.google.ortools.constraintsolver.IntVar;
|
|
import com.google.ortools.constraintsolver.Solver;
|
|
import com.google.ortools.constraintsolver.OptimizeVar;
|
|
|
|
public class SetCovering4 {
|
|
|
|
static {
|
|
System.loadLibrary("jniortools");
|
|
}
|
|
|
|
|
|
/**
|
|
*
|
|
* Solves a set covering problem.
|
|
* See http://www.hakank.org/google_or_tools/set_covering4.py
|
|
*
|
|
*/
|
|
private static void solve(int set_partition) {
|
|
|
|
Solver solver = new Solver("SetCovering4");
|
|
|
|
//
|
|
// data
|
|
//
|
|
|
|
|
|
// Set partition and set covering problem from
|
|
// Example from the Swedish book
|
|
// Lundgren, Roennqvist, Vaebrand
|
|
// 'Optimeringslaera' (translation: 'Optimization theory'),
|
|
// page 408.
|
|
int num_alternatives = 10;
|
|
int num_objects = 8;
|
|
|
|
// costs for the alternatives
|
|
int[] costs = {19, 16, 18, 13, 15, 19, 15, 17, 16, 15};
|
|
|
|
// the alternatives, and their objects
|
|
int[][] a = {
|
|
// 1 2 3 4 5 6 7 8 the objects
|
|
{1,0,0,0,0,1,0,0}, // alternative 1
|
|
{0,1,0,0,0,1,0,1}, // alternative 2
|
|
{1,0,0,1,0,0,1,0}, // alternative 3
|
|
{0,1,1,0,1,0,0,0}, // alternative 4
|
|
{0,1,0,0,1,0,0,0}, // alternative 5
|
|
{0,1,1,0,0,0,0,0}, // alternative 6
|
|
{0,1,1,1,0,0,0,0}, // alternative 7
|
|
{0,0,0,1,1,0,0,1}, // alternative 8
|
|
{0,0,1,0,0,1,0,1}, // alternative 9
|
|
{1,0,0,0,0,1,1,0}}; // alternative 10
|
|
|
|
//
|
|
// variables
|
|
//
|
|
IntVar[] x = solver.makeIntVarArray(num_alternatives, 0, 1, "x");
|
|
|
|
// number of assigned senators, to be minimize
|
|
IntVar z = solver.makeScalProd(x, costs).var();
|
|
|
|
//
|
|
// constraints
|
|
//
|
|
|
|
|
|
for(int j = 0; j < num_objects; j++) {
|
|
IntVar[] b = new IntVar[num_alternatives];
|
|
for(int i = 0; i < num_alternatives; i++) {
|
|
b[i] = solver.makeProd(x[i], a[i][j]).var();
|
|
}
|
|
|
|
if (set_partition == 1) {
|
|
solver.addConstraint(
|
|
solver.makeSumGreaterOrEqual(b, 1));
|
|
} else {
|
|
solver.addConstraint(
|
|
solver.makeSumEquality(b, 1));
|
|
}
|
|
}
|
|
|
|
//
|
|
// objective
|
|
//
|
|
OptimizeVar objective = solver.makeMinimize(z, 1);
|
|
|
|
|
|
//
|
|
// search
|
|
//
|
|
DecisionBuilder db = solver.makePhase(x,
|
|
solver.INT_VAR_DEFAULT,
|
|
solver.INT_VALUE_DEFAULT);
|
|
solver.newSearch(db, objective);
|
|
|
|
//
|
|
// output
|
|
//
|
|
while (solver.nextSolution()) {
|
|
System.out.println("z: " + z.value());
|
|
System.out.print("Selected alternatives: ");
|
|
for(int i = 0; i < num_alternatives; i++) {
|
|
if (x[i].value() == 1) {
|
|
System.out.print((1 + i) + " ");
|
|
}
|
|
}
|
|
System.out.println("\n");
|
|
}
|
|
solver.endSearch();
|
|
|
|
// Statistics
|
|
System.out.println();
|
|
System.out.println("Solutions: " + solver.solutions());
|
|
System.out.println("Failures: " + solver.failures());
|
|
System.out.println("Branches: " + solver.branches());
|
|
System.out.println("Wall time: " + solver.wallTime() + "ms");
|
|
|
|
}
|
|
|
|
public static void main(String[] args) throws Exception {
|
|
System.out.println("Set partition:");
|
|
SetCovering4.solve(1);
|
|
System.out.println("\nSet covering:");
|
|
SetCovering4.solve(0);
|
|
}
|
|
}
|