/*******************************************************************************
* SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU Lesser General Public License Version 2.1 or later (the
* "LGPL"), in which case the provisions of the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of the LGPL, and not to allow others to use your version of
* this file under the terms of the EPL, indicate your decision by deleting
* the provisions above and replace them with the notice and other provisions
* required by the LGPL. If you do not delete the provisions above, a recipient
* may use your version of this file under the terms of the EPL or the LGPL.
*
* Based on the original MiniSat specification from:
*
* An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
* Sixth International Conference on Theory and Applications of Satisfiability
* Testing, LNCS 2919, pp 502-518, 2003.
*
* See www.minisat.se for the original solver in C++.
*
*******************************************************************************/
package org.sat4j.tools;
import org.sat4j.core.VecInt;
import org.sat4j.specs.ContradictionException;
import org.sat4j.specs.ISolver;
import org.sat4j.specs.IVecInt;
import org.sat4j.specs.TimeoutException;
/**
* Computes models with a minimal number (with respect to cardinality) of
* negative literals. This is done be adding a constraint on the number of
* negative literals each time a model if found (the number of negative literals
* occuring in the model minus one).
*
* @author leberre
* @see org.sat4j.specs.ISolver#addAtMost(IVecInt, int)
*/
public class Minimal4CardinalityModel extends SolverDecorator<ISolver> {
private static final long serialVersionUID = 1L;
/**
* @param solver
*/
public Minimal4CardinalityModel(ISolver solver) {
super(solver);
}
/*
* (non-Javadoc)
*
* @see org.sat4j.ISolver#model()
*/
@Override
public int[] model() {
int[] prevmodel = null;
IVecInt vec = new VecInt();
// backUp();
try {
do {
prevmodel = super.model();
vec.clear();
for (int i = 1; i <= nVars(); i++) {
vec.push(-i);
}
int counter = 0;
for (int q : prevmodel) {
if (q < 0) {
counter++;
}
}
addAtMost(vec, counter - 1);
} while (isSatisfiable());
} catch (TimeoutException e) {
throw new IllegalStateException("Solver timed out"); //$NON-NLS-1$
} catch (ContradictionException e) {
// added trivial unsat clauses
}
// restore();
return prevmodel;
}
}