/*******************************************************************************
* 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;
    }
}