AbstractOptimizationLauncher.java

/*******************************************************************************
* 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;

import java.io.PrintWriter;

import org.sat4j.specs.ContradictionException;
import org.sat4j.specs.IOptimizationProblem;
import org.sat4j.specs.IProblem;
import org.sat4j.specs.TimeoutException;

/**
 * This class is intended to be used by launchers to solve optimization
 * problems, i.e. problems for which a loop is needed to find the optimal
 * solution.
 * 
 * @author leberre
 * 
 */
public abstract class AbstractOptimizationLauncher extends AbstractLauncher {

    /**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	
	private static final String CURRENT_OPTIMUM_VALUE_PREFIX = "o "; //$NON-NLS-1$

    @Override
    protected void displayResult() {
    	displayAnswer();

        log("Total wall clock time (in seconds): " //$NON-NLS-1$
                + (System.currentTimeMillis() - getBeginTime()) / 1000.0);
    }
    
    protected void displayAnswer(){
        if (solver == null)
            return;
        PrintWriter out = getLogWriter();
        solver.printStat(out, COMMENT_PREFIX);
        ExitCode exitCode = getExitCode();
        out.println(ANSWER_PREFIX + exitCode);
        if (exitCode == ExitCode.SATISFIABLE
                || exitCode == ExitCode.OPTIMUM_FOUND) {
            out.print(SOLUTION_PREFIX);
            getReader().decode(solver.model(), out);
            out.println();
            IOptimizationProblem optproblem = (IOptimizationProblem) solver;
            if (!optproblem.hasNoObjectiveFunction()) {
                log("objective function=" + optproblem.calculateObjective()); //$NON-NLS-1$
            }
        }
    }

    @Override
    protected void solve(IProblem problem) throws TimeoutException {
        boolean isSatisfiable = false;

        IOptimizationProblem optproblem = (IOptimizationProblem) problem;

        try {
            while (optproblem.admitABetterSolution()) {
                if (!isSatisfiable) {
                    if (optproblem.nonOptimalMeansSatisfiable()) {
                        setExitCode(ExitCode.SATISFIABLE);
                        if (optproblem.hasNoObjectiveFunction()) {
                            return;
                        }
                        log("SATISFIABLE"); //$NON-NLS-1$
                    }
                    isSatisfiable = true;
                    log("OPTIMIZING..."); //$NON-NLS-1$
                }
                log("Got one! Elapsed wall clock time (in seconds):" //$NON-NLS-1$
                        + (System.currentTimeMillis() - getBeginTime())
                        / 1000.0);
                getLogWriter().println(
                        CURRENT_OPTIMUM_VALUE_PREFIX
                                + optproblem.calculateObjective());
                optproblem.discard();
            }
            if (isSatisfiable) {
                setExitCode(ExitCode.OPTIMUM_FOUND);
            } else {
                setExitCode(ExitCode.UNSATISFIABLE);
            }
        } catch (ContradictionException ex) {
            assert isSatisfiable;
            setExitCode(ExitCode.OPTIMUM_FOUND);
        }
    }

}