Constr.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.minisat.core;

import org.sat4j.specs.IConstr;
import org.sat4j.specs.IVecInt;

/*
 * Created on 16 oct. 2003
 */

/**
 * Basic constraint abstraction used in Solver.
 * 
 * Any new constraint type should implement that interface.
 * 
 * @author leberre
 */
public interface Constr extends Propagatable, IConstr {

    /**
     * Remove a constraint from the solver.
     * 
     */
    void remove();

    /**
     * Simplifies a constraint, by removing top level falsified literals for
     * instance.
     * 
     * @return true iff the constraint is satisfied.
     */
    boolean simplify();

    /**
     * Compute the reason for a given assignment.
     * 
     * If the constraint is a clause, it is supposed to be either a unit clause
     * or a falsified one.
     * 
     * @param p
     *            a satisfied literal (or Lit.UNDEFINED)
     * @param outReason
     *            the list of falsified literals whose negation is the reason of
     *            the assignment of p to true.
     */
    void calcReason(int p, IVecInt outReason);

    /**
     * Increase the constraint activity.
     * 
     * @param claInc
     *            the value to increase the activity with
     */
    void incActivity(double claInc);

    /**
     * To obtain the activity of the constraint.
     * 
     * @return the activity of the clause.
     */
    double getActivity();

    /**
     * Indicate wether a constraint is responsible from an assignment.
     * 
     * @return true if a constraint is a "reason" for an assignment.
     */
    boolean locked();

    /**
     * Mark a constraint as learnt.
     */

    void setLearnt();

    /**
     * Register the constraint to the solver.
     */
    void register();

    /**
     * Rescale the clause activity by a value.
     * 
     * @param d
     *            the value to rescale the clause activity with.
     */
    void rescaleBy(double d);

    /**
     * Method called when the constraint is to be asserted. It means that the
     * constraint was learnt during the search and it should now propagate some
     * truth values. In the clausal case, only one literal should be propagated.
     * In other cases, it might be different.
     * 
     * @param s
     *            a UnitPropagationListener to use for unit propagation.
     */
    void assertConstraint(UnitPropagationListener s);
}