1 /*
2 * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2006 Daniel Le Berre
3 *
4 * Based on the original minisat specification from:
5 *
6 * An extensible SAT solver. Niklas E?n and Niklas S?rensson. Proceedings of the
7 * Sixth International Conference on Theory and Applications of Satisfiability
8 * Testing, LNCS 2919, pp 502-518, 2003.
9 *
10 * This library is free software; you can redistribute it and/or modify it under
11 * the terms of the GNU Lesser General Public License as published by the Free
12 * Software Foundation; either version 2.1 of the License, or (at your option)
13 * any later version.
14 *
15 * This library is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
18 * details.
19 *
20 * You should have received a copy of the GNU Lesser General Public License
21 * along with this library; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 *
24 */
25 package org.sat4j.opt;
26
27 import java.io.Serializable;
28 import java.math.BigInteger;
29
30 import org.sat4j.core.Vec;
31 import org.sat4j.core.VecInt;
32 import org.sat4j.specs.IVec;
33 import org.sat4j.specs.IVecInt;
34
35 /**
36 * Abstraction for an Objective Function for Pseudo Boolean Optimization.
37 *
38 * May be generalized in the future to deal with other optimization functions.
39 *
40 * @author leberre
41 *
42 */
43 public class ObjectiveFunction implements Serializable {
44
45 /**
46 *
47 */
48 private static final long serialVersionUID = 1L;
49
50 // contains the coeffs of the objective function for each variable
51 private final IVec<BigInteger> coeffs;
52
53 private final IVecInt vars;
54
55 public ObjectiveFunction(IVecInt vars, IVec<BigInteger> coeffs) {
56 this.vars = new VecInt(vars.size());
57 vars.copyTo(this.vars);
58 this.coeffs = new Vec<BigInteger>(coeffs.size());
59 coeffs.copyTo(this.coeffs);
60 }
61
62 // calculate the degree of the objectif function
63 public BigInteger calculateDegree(int[] model) {
64 BigInteger tempDegree = BigInteger.ZERO;
65
66 for (int i = 0; i < vars.size(); i++) {
67 if (varInModel(vars.get(i), model))
68 tempDegree = tempDegree.add(coeffs.get(i));
69 }
70 return tempDegree;
71 }
72
73 private boolean varInModel(int var, int[] model) {
74 for (int i = 0; i < model.length; i++)
75 if (var == model[i])
76 return true;
77 return false;
78 }
79
80 public IVec<BigInteger> getCoeffs() {
81 IVec<BigInteger> coefbis = new Vec<BigInteger>(coeffs.size());
82 coeffs.copyTo(coefbis);
83 return coefbis;
84 }
85
86 public IVecInt getVars() {
87 IVecInt varbis = new VecInt(vars.size());
88 vars.copyTo(varbis);
89 return varbis;
90 }
91
92 }