Solver

/*******************************************************************************
 * SAT4J: a SATisfiability library for Java Copyright (C) 2004, 2012 Artois University and CNRS
 *
 * 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++.
 *
 * Contributors:
 *   CRIL - initial API and implementation
 *******************************************************************************/
package org.sat4j.minisat.core;

import static org.sat4j.core.LiteralsUtils.neg;
import static org.sat4j.core.LiteralsUtils.toDimacs;
import static org.sat4j.core.LiteralsUtils.toInternal;
import static org.sat4j.core.LiteralsUtils.var;

import java.io.PrintStream;
import java.io.PrintWriter;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Timer;
import java.util.TimerTask;

import org.sat4j.core.ConstrGroup;
import org.sat4j.core.LiteralsUtils;
import org.sat4j.core.Vec;
import org.sat4j.core.VecInt;
import org.sat4j.specs.ContradictionException;
import org.sat4j.specs.IConstr;
import org.sat4j.specs.ILogAble;
import org.sat4j.specs.ISolver;
import org.sat4j.specs.ISolverService;
import org.sat4j.specs.IVec;
import org.sat4j.specs.IVecInt;
import org.sat4j.specs.IteratorInt;
import org.sat4j.specs.Lbool;
import org.sat4j.specs.SearchListener;
import org.sat4j.specs.TimeoutException;

/**
 * The backbone of the library providing the modular implementation of a MiniSAT
 * (Chaff) like solver.
 *
 * @author leberre
 */
public class Solver<D extends DataStructureFactory> implements ISolverService,
        ICDCL<D> {

    private static final long serialVersionUID = 1L;

    private static final double CLAUSE_RESCALE_FACTOR = 1e-20;

    private static final double CLAUSE_RESCALE_BOUND = 1 / CLAUSE_RESCALE_FACTOR;

    protected ILogAble out;

    /**
     * Set of original constraints.
     */
    protected final IVec<Constr> constrs = new Vec<Constr>();

    /**
     * Set of learned constraints.
     */
    protected final IVec<Constr> learnts = new Vec<Constr>();

    /**
     * Increment for clause activity.
     */
    private double claInc = 1.0;

    /**
     * decay factor pour l'activit? des clauses.
     */
    private double claDecay = 1.0;

    /**
     * propagation queue
     */
    // head of the queue in trail ... (taken from MiniSAT 1.14)
    private int qhead = 0;

    /**
     * variable assignments (literals) in chronological order.
     */
    protected final IVecInt trail = new VecInt();

    /**
     * position of the decision levels on the trail.
     */
    protected final IVecInt trailLim = new VecInt();

    /**
     * position of assumptions before starting the search.
     */
    protected int rootLevel;

    private int[] model = null;

    protected ILits voc;

    private IOrder order;

    private final ActivityComparator comparator = new ActivityComparator();

    private SolverStats stats = new SolverStats();

    private LearningStrategy<D> learner;

    protected volatile boolean undertimeout;

    private long timeout = Integer.MAX_VALUE;

    private boolean timeBasedTimeout = true;

    protected D dsfactory;

    private SearchParams params;

    private final IVecInt __dimacs_out = new VecInt();

    protected SearchListener slistener = new VoidTracing();

    private RestartStrategy restarter;

    private final Map<String, Counter> constrTypes = new HashMap<String, Counter>();

    private boolean isDBSimplificationAllowed = false;

    private final IVecInt learnedLiterals = new VecInt();

    private boolean verbose = false;

    private boolean keepHot = false;

    private String prefix = "c ";
    private int declaredMaxVarId = 0;

    protected IVecInt dimacs2internal(IVecInt in) {
        this.__dimacs_out.clear();
        this.__dimacs_out.ensure(in.size());
        int p;
        for (int i = 0; i < in.size(); i++) {
            p = in.get(i);
            if (p == 0) {
                throw new IllegalArgumentException(
                        "0 is not a valid variable identifier");
            }
            this.__dimacs_out.unsafePush(this.voc.getFromPool(p));
        }
        return this.__dimacs_out;
    }

    /*
     * @since 2.3.1
     */
    public void registerLiteral(int p) {
        this.voc.getFromPool(p);
    }

    /**
     * creates a Solver without LearningListener. A learningListener must be
     * added to the solver, else it won't backtrack!!! A data structure factory
     * must be provided, else it won't work either.
     */

    public Solver(LearningStrategy<D> learner, D dsf, IOrder order,
            RestartStrategy restarter) {
        this(learner, dsf, new SearchParams(), order, restarter);
    }

    public Solver(LearningStrategy<D> learner, D dsf, SearchParams params,
            IOrder order, RestartStrategy restarter) {
        this(learner, dsf, params, order, restarter, ILogAble.CONSOLE);
    }

    public Solver(LearningStrategy<D> learner, D dsf, SearchParams params,
            IOrder order, RestartStrategy restarter, ILogAble logger) {
        this.order = order;
        this.params = params;
        this.restarter = restarter;
        this.out = logger;
        setDataStructureFactory(dsf);
        // should be called after dsf has been set up
        setLearningStrategy(learner);
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#setDataStructureFactory(D)
     */
    public final void setDataStructureFactory(D dsf) {
        this.dsfactory = dsf;
        this.dsfactory.setUnitPropagationListener(this);
        this.dsfactory.setLearner(this);
        this.voc = dsf.getVocabulary();
        this.order.setLits(this.voc);
    }

    /**
     * @since 2.2
     */
    public boolean isVerbose() {
        return this.verbose;
    }

    /**
     * @param value
     * @since 2.2
     */
    public void setVerbose(boolean value) {
        this.verbose = value;
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.sat4j.minisat.core.ICDCL#setSearchListener(org.sat4j.specs.SearchListener
     * )
     */
    public <S extends ISolverService> void setSearchListener(
            SearchListener<S> sl) {
        this.slistener = sl;
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#getSearchListener()
     */
    public <S extends ISolverService> SearchListener<S> getSearchListener() {
        return this.slistener;
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#setLearner(org.sat4j.minisat.core.
     * LearningStrategy)
     */
    public void setLearner(LearningStrategy<D> strategy) {
        setLearningStrategy(strategy);
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.sat4j.minisat.core.ICDCL#setLearningStrategy(org.sat4j.minisat.core.
     * LearningStrategy)
     */
    public void setLearningStrategy(LearningStrategy<D> strategy) {
        if (this.learner != null) {
            this.learner.setSolver(null);
        }
        this.learner = strategy;
        strategy.setSolver(this);
    }

    public void setTimeout(int t) {
        this.timeout = t * 1000L;
        this.timeBasedTimeout = true;
    }

    public void setTimeoutMs(long t) {
        this.timeout = t;
        this.timeBasedTimeout = true;
    }

    public void setTimeoutOnConflicts(int count) {
        this.timeout = count;
        this.timeBasedTimeout = false;
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#setSearchParams(org.sat4j.minisat.core.
     * SearchParams)
     */
    public void setSearchParams(SearchParams sp) {
        this.params = sp;
    }

    public SearchParams getSearchParams() {
        return this.params;
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.sat4j.minisat.core.ICDCL#setRestartStrategy(org.sat4j.minisat.core
     * .RestartStrategy)
     */
    public void setRestartStrategy(RestartStrategy restarter) {
        this.restarter = restarter;
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#getRestartStrategy()
     */
    public RestartStrategy getRestartStrategy() {
        return this.restarter;
    }

    public void expireTimeout() {
        this.undertimeout = false;
        if (this.timeBasedTimeout) {
            if (this.timer != null) {
                this.timer.cancel();
                this.timer = null;
            }
        } else {
            if (this.conflictCount != null) {
                this.conflictCount = null;
            }
        }
    }

    protected int nAssigns() {
        return this.trail.size();
    }

    public int nConstraints() {
        return this.constrs.size();
    }

    public void learn(Constr c) {
        this.slistener.learn(c);
        this.learnts.push(c);
        c.setLearnt();
        c.register();
        this.stats.learnedclauses++;
        switch (c.size()) {
        case 2:
            this.stats.learnedbinaryclauses++;
            break;
        case 3:
            this.stats.learnedternaryclauses++;
            break;
        default:
            // do nothing
        }
    }

    public final int decisionLevel() {
        return this.trailLim.size();
    }

    @Deprecated
    public int newVar() {
        int index = this.voc.nVars() + 1;
        this.voc.ensurePool(index);
        return index;
    }

    public int newVar(int howmany) {
        this.voc.ensurePool(howmany);
        this.declaredMaxVarId = howmany;
        return howmany;
    }

    public IConstr addClause(IVecInt literals) throws ContradictionException {
        IVecInt vlits = dimacs2internal(literals);
        return addConstr(this.dsfactory.createClause(vlits));
    }

    public boolean removeConstr(IConstr co) {
        if (co == null) {
            throw new IllegalArgumentException(
                    "Reference to the constraint to remove needed!"); //$NON-NLS-1$
        }
        Constr c = (Constr) co;
        c.remove(this);
        this.constrs.remove(c);
        clearLearntClauses();
        String type = c.getClass().getName();
        this.constrTypes.get(type).dec();
        return true;
    }

    /**
     * @since 2.1
     */
    public boolean removeSubsumedConstr(IConstr co) {
        if (co == null) {
            throw new IllegalArgumentException(
                    "Reference to the constraint to remove needed!"); //$NON-NLS-1$
        }
        if (this.constrs.last() != co) {
            throw new IllegalArgumentException(
                    "Can only remove latest added constraint!!!"); //$NON-NLS-1$
        }
        Constr c = (Constr) co;
        c.remove(this);
        this.constrs.pop();
        String type = c.getClass().getName();
        this.constrTypes.get(type).dec();
        return true;
    }

    public void addAllClauses(IVec<IVecInt> clauses)
            throws ContradictionException {
        for (Iterator<IVecInt> iterator = clauses.iterator(); iterator
                .hasNext();) {
            addClause(iterator.next());
        }
    }

    public IConstr addAtMost(IVecInt literals, int degree)
            throws ContradictionException {
        int n = literals.size();
        IVecInt opliterals = new VecInt(n);
        for (IteratorInt iterator = literals.iterator(); iterator.hasNext();) {
            opliterals.push(-iterator.next());
        }
        return addAtLeast(opliterals, n - degree);
    }

    public IConstr addAtLeast(IVecInt literals, int degree)
            throws ContradictionException {
        IVecInt vlits = dimacs2internal(literals);
        return addConstr(this.dsfactory.createCardinalityConstraint(vlits,
                degree));
    }

    public IConstr addExactly(IVecInt literals, int n)
            throws ContradictionException {
        ConstrGroup group = new ConstrGroup(false);
        group.add(addAtMost(literals, n));
        group.add(addAtLeast(literals, n));
        return group;
    }

    @SuppressWarnings("unchecked")
    public boolean simplifyDB() {
        // Simplifie la base de clauses apres la premiere propagation des
        // clauses unitaires
        IVec<Constr>[] cs = new IVec[] { this.constrs, this.learnts };
        for (int type = 0; type < 2; type++) {
            int j = 0;
            for (int i = 0; i < cs[type].size(); i++) {
                if (cs[type].get(i).simplify()) {
                    // enleve les contraintes satisfaites de la base
                    cs[type].get(i).remove(this);
                } else {
                    cs[type].moveTo(j++, i);
                }
            }
            cs[type].shrinkTo(j);
        }
        return true;
    }

    /**
     * Si un mod?le est trouv?, ce vecteur contient le mod?le.
     *
     * @return un mod?le de la formule.
     */
    public int[] model() {
        if (this.model == null) {
            throw new UnsupportedOperationException(
                    "Call the solve method first!!!"); //$NON-NLS-1$
        }
        int[] nmodel = new int[this.model.length];
        System.arraycopy(this.model, 0, nmodel, 0, this.model.length);
        return nmodel;
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#enqueue(int)
     */
    public boolean enqueue(int p) {
        return enqueue(p, null);
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#enqueue(int,
     * org.sat4j.minisat.core.Constr)
     */
    public boolean enqueue(int p, Constr from) {
        assert p > 1;
        if (this.voc.isSatisfied(p)) {
            // literal is already satisfied. Skipping.
            return true;
        }
        if (this.voc.isFalsified(p)) {
            // conflicting enqueued assignment
            return false;
        }
        // new fact, store it
        this.voc.satisfies(p);
        this.voc.setLevel(p, decisionLevel());
        this.voc.setReason(p, from);
        this.trail.push(p);
        if (from != null && from.learnt()) {
            this.learnedConstraintsDeletionStrategy.onPropagation(from);
        }
        return true;
    }

    private boolean[] mseen = new boolean[0];

    private final IVecInt mpreason = new VecInt();

    private final IVecInt moutLearnt = new VecInt();

    /**
     * @throws TimeoutException
     *             if the timeout is reached during conflict analysis.
     */
    public void analyze(Constr confl, Pair results) throws TimeoutException {
        assert confl != null;

        final boolean[] seen = this.mseen;
        final IVecInt outLearnt = this.moutLearnt;
        final IVecInt preason = this.mpreason;

        outLearnt.clear();
        assert outLearnt.size() == 0;
        for (int i = 0; i < seen.length; i++) {
            seen[i] = false;
        }

        int counter = 0;
        int p = ILits.UNDEFINED;

        outLearnt.push(ILits.UNDEFINED);
        // reserve de la place pour le litteral falsifie
        int outBtlevel = 0;
        IConstr prevConfl = null;

        do {
            preason.clear();
            assert confl != null;
            if (prevConfl != confl) {
                confl.calcReason(p, preason);
                this.learnedConstraintsDeletionStrategy
                        .onConflictAnalysis(confl);
                // Trace reason for p
                for (int j = 0; j < preason.size(); j++) {
                    int q = preason.get(j);
                    this.order.updateVar(q);
                    if (!seen[q >> 1]) {
                        seen[q >> 1] = true;
                        if (this.voc.getLevel(q) == decisionLevel()) {
                            counter++;
                            this.order.updateVarAtDecisionLevel(q);
                        } else if (this.voc.getLevel(q) > 0) {
                            // only literals assigned after decision level 0
                            // part of
                            // the explanation
                            outLearnt.push(q ^ 1);
                            outBtlevel = Math.max(outBtlevel,
                                    this.voc.getLevel(q));
                        }
                    }
                }
            }
            prevConfl = confl;
            // select next reason to look at
            do {
                p = this.trail.last();
                confl = this.voc.getReason(p);
                undoOne();
            } while (!seen[p >> 1]);
            // seen[p.var] indique que p se trouve dans outLearnt ou dans
            // le dernier niveau de d?cision
        } while (--counter > 0);

        outLearnt.set(0, p ^ 1);
        this.simplifier.simplify(outLearnt);

        Constr c = this.dsfactory.createUnregisteredClause(outLearnt);
        // slistener.learn(c);
        this.learnedConstraintsDeletionStrategy.onClauseLearning(c);
        results.reason = c;

        assert outBtlevel > -1;
        results.backtrackLevel = outBtlevel;
    }

    /**
     * Derive a subset of the assumptions causing the inconistency.
     *
     * @param confl
     *            the last conflict of the search, occuring at root level.
     * @param assumps
     *            the set of assumption literals
     * @param conflictingLiteral
     *            the literal detected conflicting while propagating
     *            assumptions.
     * @return a subset of assumps causing the inconsistency.
     * @since 2.2
     */
    public IVecInt analyzeFinalConflictInTermsOfAssumptions(Constr confl,
            IVecInt assumps, int conflictingLiteral) {
        if (assumps.size() == 0) {
            return null;
        }
        while (!this.trailLim.isEmpty()
                && this.trailLim.last() == this.trail.size()) {
            // conflict detected when assuming a value
            this.trailLim.pop();
        }
        final boolean[] seen = this.mseen;
        final IVecInt outLearnt = this.moutLearnt;
        final IVecInt preason = this.mpreason;

        outLearnt.clear();
        if (this.trailLim.size() == 0) {
            // conflict detected on unit clauses
            return outLearnt;
        }

        assert outLearnt.size() == 0;
        for (int i = 0; i < seen.length; i++) {
            seen[i] = false;
        }

        if (confl == null) {
            seen[conflictingLiteral >> 1] = true;
        }

        int p = ILits.UNDEFINED;
        while (confl == null && this.trail.size() > 0
                && this.trailLim.size() > 0) {
            p = this.trail.last();
            confl = this.voc.getReason(p);
            undoOne();
            if (confl == null && p == (conflictingLiteral ^ 1)) {
                outLearnt.push(toDimacs(p));
            }
            if (this.trail.size() <= this.trailLim.last()) {
                this.trailLim.pop();
            }
        }
        if (confl == null) {
            return outLearnt;
        }
        do {

            preason.clear();
            confl.calcReason(p, preason);
            // Trace reason for p
            for (int j = 0; j < preason.size(); j++) {
                int q = preason.get(j);
                if (!seen[q >> 1]) {
                    seen[q >> 1] = true;
                    if (this.voc.getReason(q) == null
                            && this.voc.getLevel(q) > 0) {
                        assert assumps.contains(toDimacs(q));
                        outLearnt.push(toDimacs(q));
                    }
                }
            }

            // select next reason to look at
            do {
                p = this.trail.last();
                confl = this.voc.getReason(p);
                undoOne();
                if (decisionLevel() > 0
                        && this.trail.size() <= this.trailLim.last()) {
                    this.trailLim.pop();
                }
            } while (this.trail.size() > 0 && decisionLevel() > 0
                    && (!seen[p >> 1] || confl == null));
        } while (decisionLevel() > 0);
        return outLearnt;
    }

    public static final ISimplifier NO_SIMPLIFICATION = new ISimplifier() {
        /**
         *
         */
        private static final long serialVersionUID = 1L;

        public void simplify(IVecInt outLearnt) {
        }

        @Override
        public String toString() {
            return "No reason simplification"; //$NON-NLS-1$
        }
    };

    public final ISimplifier SIMPLE_SIMPLIFICATION = new ISimplifier() {
        /**
         *
         */
        private static final long serialVersionUID = 1L;

        public void simplify(IVecInt conflictToReduce) {
            simpleSimplification(conflictToReduce);
        }

        @Override
        public String toString() {
            return "Simple reason simplification"; //$NON-NLS-1$
        }
    };

    public final ISimplifier EXPENSIVE_SIMPLIFICATION = new ISimplifier() {

        /**
         *
         */
        private static final long serialVersionUID = 1L;

        public void simplify(IVecInt conflictToReduce) {
            expensiveSimplification(conflictToReduce);
        }

        @Override
        public String toString() {
            return "Expensive reason simplification"; //$NON-NLS-1$
        }
    };

    public final ISimplifier EXPENSIVE_SIMPLIFICATION_WLONLY = new ISimplifier() {

        /**
         *
         */
        private static final long serialVersionUID = 1L;

        public void simplify(IVecInt conflictToReduce) {
            expensiveSimplificationWLOnly(conflictToReduce);
        }

        @Override
        public String toString() {
            return "Expensive reason simplification specific for WL data structure"; //$NON-NLS-1$
        }
    };

    private ISimplifier simplifier = NO_SIMPLIFICATION;

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#setSimplifier(java.lang.String)
     */
    public void setSimplifier(SimplificationType simp) {
        Field f;
        try {
            f = Solver.class.getDeclaredField(simp.toString());
            this.simplifier = (ISimplifier) f.get(this);
        } catch (Exception e) {
            e.printStackTrace();
            this.simplifier = NO_SIMPLIFICATION;
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.sat4j.minisat.core.ICDCL#setSimplifier(org.sat4j.minisat.core.Solver
     * .ISimplifier)
     */
    public void setSimplifier(ISimplifier simp) {
        this.simplifier = simp;
    }

    /*
     * (non-Javadoc)
     *
     * @see org.sat4j.minisat.core.ICDCL#getSimplifier()
     */
    public ISimplifier getSimplifier() {
        return this.simplifier;
    }

    // MiniSat -- Copyright (c) 2003-2005, Niklas Een, Niklas Sorensson
    //
    // Permission is hereby granted, free of charge, to any person obtaining a
    // copy of this software and associated documentation files (the
    // "Software"), to deal in the Software without restriction, including
    // without limitation the rights to use, copy, modify, merge, publish,
    // distribute, sublicense, and/or sell copies of the Software, and to
    // permit persons to whom the Software is furnished to do so, subject to
    // the following conditions:
    //
    // The above copyright notice and this permission notice shall be included
    // in all copies or substantial portions of the Software.
    //
    // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
    // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
    // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
    // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
    // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    // Taken from MiniSAT 1.14: Simplify conflict clause (a little):
    private void simpleSimplification(IVecInt conflictToReduce) {
        int i, j, p;
        final boolean[] seen = this.mseen;
        IConstr r;
        for (i = j = 1; i < conflictToReduce.size(); i++) {
            r = this.voc.getReason(conflictToReduce.get(i));
            if (r == null || r.canBePropagatedMultipleTimes()) {
                conflictToReduce.moveTo(j++, i);
            } else {
                for (int k = 0; k < r.size(); k++) {
                    p = r.get(k);
                    if (!seen[p >> 1] && this.voc.isFalsified(p)
                            && this.voc.getLevel(p) != 0) {
                        conflictToReduce.moveTo(j++, i);
                        break;
                    }
                }
            }
        }
        conflictToReduce.shrink(i - j);
        this.stats.reducedliterals += i - j;
    }

    private final IVecInt analyzetoclear = new VecInt();

    private final IVecInt analyzestack = new VecInt();

    // Taken from MiniSAT 1.14
    private void expensiveSimplification(IVecInt conflictToReduce) {
        // Simplify conflict clause (a lot):
        //
        int i, j;
        // (maintain an abstraction of levels involved in conflict)
        this.analyzetoclear.clear();
        conflictToReduce.copyTo(this.analyzetoclear);
        for (i = 1, j = 1; i < conflictToReduce.size(); i++) {
            if (this.voc.getReason(conflictToReduce.get(i)) == null
                    || !analyzeRemovable(conflictToReduce.get(i))) {
                conflictToReduce.moveTo(j++, i);
            }
        }
        conflictToReduce.shrink(i - j);
        this.stats.reducedliterals += i - j;
    }

    // Check if 'p' can be removed.' min_level' is used to abort early if
    // visiting literals at a level that cannot be removed.
    //
    private boolean analyzeRemovable(int p) {
        assert this.voc.getReason(p) != null;
        ILits lvoc = this.voc;
        IVecInt lanalyzestack = this.analyzestack;
        IVecInt lanalyzetoclear = this.analyzetoclear;
        lanalyzestack.clear();
        lanalyzestack.push(p);
        final boolean[] seen = this.mseen;
        int top = lanalyzetoclear.size();
        while (lanalyzestack.size() > 0) {
            int q = lanalyzestack.last();
            assert lvoc.getReason(q) != null;
            Constr c = lvoc.getReason(q);
            lanalyzestack.pop();
            if (c.canBePropagatedMultipleTimes()) {
                for (int j = top; j < lanalyzetoclear.size(); j++) {
                    seen[lanalyzetoclear.get(j) >> 1] = false;
                }
                lanalyzetoclear.shrink(lanalyzetoclear.size() - top);
                return false;
            }
            for (int i = 0; i < c.size(); i++) {
                int l = c.get(i);
                if (!seen[var(l)] && lvoc.isFalsified(l)
                        && lvoc.getLevel(l) != 0) {
                    if (lvoc.getReason(l) == null) {
                        for (int j = top; j < lanalyzetoclear.size(); j++) {
                            seen[lanalyzetoclear.get(j) >> 1] = false;
                        }
                        lanalyzetoclear.shrink(lanalyzetoclear.size() - top);
                        return false;
                    }
                    seen[l >> 1] = true;
                    lanalyzestack.push(l);
                    lanalyzetoclear.push(l);
                }
            }

        }

        return true;
    }

    // Taken from MiniSAT 1.14
    private void expensiveSimplificationWLOnly(IVecInt conflictToReduce) {
        // Simplify conflict clause (a lot):
        //
        int i, j;
        // (maintain an abstraction of levels involved in conflict)
        this.analyzetoclear.clear();
        conflictToReduce.copyTo(this.analyzetoclear);
        for (i = 1, j = 1; i < conflictToReduce.size(); i++) {
            if (this.voc.getReason(conflictToReduce.get(i)) == null
                    || !analyzeRemovableWLOnly(conflictToReduce.get(i))) {
                conflictToReduce.moveTo(j++, i);
            }
        }
        conflictToReduce.shrink(i - j);
        this.stats.reducedliterals += i - j;
    }

    // Check if 'p' can be removed.' min_level' is used to abort early if
    // visiting literals at a level that cannot be removed.
    //
    private boolean analyzeRemovableWLOnly(int p) {
        assert this.voc.getReason(p) != null;
        this.analyzestack.clear();
        this.analyzestack.push(p);
        final boolean[] seen = this.mseen;
        int top = this.analyzetoclear.size();
        while (this.analyzestack.size() > 0) {
            int q = this.analyzestack.last();
            assert this.voc.getReason(q) != null;
            Constr c = this.voc.getReason(q);
            this.analyzestack.pop();
            for (int i = 1; i < c.size(); i++) {
                int l = c.get(i);
                if (!seen[var(l)] && this.voc.getLevel(l) != 0) {
                    if (this.voc.getReason(l) == null) {
                        for (int j = top; j < this.analyzetoclear.size(); j++) {
                            seen[this.analyzetoclear.get(j) >> 1] = false;
                        }
                        this.analyzetoclear.shrink(this.analyzetoclear.size()
                                - top);
                        return false;
                    }
                    seen[l >> 1] = true;
                    this.analyzestack.push(l);
                    this.analyzetoclear.push(l);
                }
            }
        }

        return true;
    }

    // END Minisat 1.14 cut and paste

    /**
     *
     */
    protected void undoOne() {
        // gather last assigned literal
        int p = this.trail.last();
        assert p > 1;
        assert this.voc.getLevel(p) >= 0;
        int x = p >> 1;
        // unassign variable
        this.voc.unassign(p);
        this.voc.setReason(p, null);
        this.voc.setLevel(p, -1);
        // update heuristics value
        this.order.undo(x);
        // remove literal from the trail
        this.trail.pop();
        // update constraints on backtrack.
        // not used if the solver uses watched literals.
        IVec<Undoable> undos = this.voc.undos(p);
        assert undos != null;
        for (int size = undos.size(); size > 0; size--) {
            undos.last().undo(p);
            undos.pop();
        }
     }

     /**
      * Propagate activity to a constraint
      *
      * @param confl
      *            a constraint
      */
     public void claBumpActivity(Constr confl) {
         confl.incActivity(this.claInc);
         if (confl.getActivity() > CLAUSE_RESCALE_BOUND) {
             claRescalActivity();
             // for (int i = 0; i < confl.size(); i++) {
             // varBumpActivity(confl.get(i));
             // }
         }
     }

     public void varBumpActivity(int p) {
         this.order.updateVar(p);
     }

     private void claRescalActivity() {
         for (int i = 0; i < this.learnts.size(); i++) {
             this.learnts.get(i).rescaleBy(CLAUSE_RESCALE_FACTOR);
         }
         this.claInc *= CLAUSE_RESCALE_FACTOR;
     }

     private final IVec<Propagatable> watched = new Vec<Propagatable>();

     /**
      * @return null if not conflict is found, else a conflicting constraint.
      */
     public final Constr propagate() {
         IVecInt ltrail = this.trail;
         SolverStats lstats = this.stats;
         IOrder lorder = this.order;
         SearchListener lslistener = this.slistener;
         // ltrail.size() changes due to propagation
         // cannot cache that value.
         while (this.qhead < ltrail.size()) {
             lstats.propagations++;
             int p = ltrail.get(this.qhead++);
             lslistener.propagating(toDimacs(p), null);
             lorder.assignLiteral(p);
             Constr confl = reduceClausesForFalsifiedLiteral(p);
             if (confl != null) {
                 return confl;
             }
         }
         return null;
     }

     private Constr reduceClausesForFalsifiedLiteral(int p) {
         // p is the literal to propagate
         // Moved original MiniSAT code to dsfactory to avoid
         // watches manipulation in counter Based clauses for instance.
         assert p > 1;
         IVec<Propagatable> lwatched = this.watched;
         lwatched.clear();
         this.voc.watches(p).moveTo(lwatched);
         final int size = lwatched.size();
         for (int i = 0; i < size; i++) {
             this.stats.inspects++;
             // try shortcut
             // shortcut = shortcuts.get(i);
             // if (shortcut != ILits.UNDEFINED && voc.isSatisfied(shortcut))
             // {
             // voc.watch(p, watched.get(i), shortcut);
             // stats.shortcuts++;
             // continue;
             // }
             if (!lwatched.get(i).propagate(this, p)) {
                 // Constraint is conflicting: copy remaining watches to
                 // watches[p]
                 // and return constraint
                 final int sizew = lwatched.size();
                 for (int j = i + 1; j < sizew; j++) {
                     this.voc.watch(p, lwatched.get(j));
                 }
                 this.qhead = this.trail.size(); // propQ.clear();
                 return lwatched.get(i).toConstraint();
             }
         }
         return null;
     }

     void record(Constr constr) {
         constr.assertConstraint(this);
         this.slistener.adding(toDimacs(constr.get(0)));
         if (constr.size() == 1) {
             this.stats.learnedliterals++;
         } else {
             this.learner.learns(constr);
         }
     }

     /**
      * @return false ssi conflit imm?diat.
      */
     public boolean assume(int p) {
         // Precondition: assume propagation queue is empty
         assert this.trail.size() == this.qhead;
         assert !this.trailLim.contains(this.trail.size());
         this.trailLim.push(this.trail.size());
         return enqueue(p);
     }

     /**
      * Revert to the state before the last assume()
      */
     private void cancel() {
         // assert trail.size() == qhead || !undertimeout;
         int decisionvar = this.trail.unsafeGet(this.trailLim.last());
         this.slistener.backtracking(toDimacs(decisionvar));
         for (int c = this.trail.size() - this.trailLim.last(); c > 0; c--) {
             undoOne();
         }
         this.trailLim.pop();
         this.qhead = this.trail.size();
     }

     /**
      * Restore literals
      */
     private void cancelLearntLiterals(int learnedLiteralsLimit) {
         this.learnedLiterals.clear();
         // assert trail.size() == qhead || !undertimeout;
         while (this.trail.size() > learnedLiteralsLimit) {
             this.learnedLiterals.push(this.trail.last());
             undoOne();
         }
         // qhead = 0;
         // learnedLiterals = 0;
     }

     /**
      * Cancel several levels of assumptions
      *
      * @param level
      */
     protected void cancelUntil(int level) {
         while (decisionLevel() > level) {
             cancel();
         }
     }

     private final Pair analysisResult = new Pair();

     private boolean[] userbooleanmodel;

     private IVecInt unsatExplanationInTermsOfAssumptions;

     Lbool search(IVecInt assumps) {
         assert this.rootLevel == decisionLevel();
         this.stats.starts++;
         int backjumpLevel;

         // varDecay = 1 / params.varDecay;
         this.order.setVarDecay(1 / this.params.getVarDecay());
         this.claDecay = 1 / this.params.getClaDecay();

         do {
             this.slistener.beginLoop();
             // propage les clauses unitaires
             Constr confl = propagate();
             assert this.trail.size() == this.qhead;

             if (confl == null) {
                 // No conflict found
                 // simpliFYDB() prevents a correct use of
                 // constraints removal.
                 if (decisionLevel() == 0 && this.isDBSimplificationAllowed) {
                     // // Simplify the set of problem clause
                     // // iff rootLevel==0
                     this.stats.rootSimplifications++;
                     boolean ret = simplifyDB();
                     assert ret;
                 }
                 // was learnts.size() - nAssigns() > nofLearnts
                 // if (nofLearnts.obj >= 0 && learnts.size() > nofLearnts.obj) {
                 assert nAssigns() <= this.voc.realnVars();
                 if (nAssigns() == this.voc.realnVars()) {
                     modelFound();
                     this.slistener
                             .solutionFound((this.fullmodel != null) ? this.fullmodel
                                     : this.model, this);
                     if (this.sharedConflict == null) {
                         cancelUntil(this.rootLevel);
                         return Lbool.TRUE;
                     } else {
                         // listener called ISolverService.backtrack()
                         confl = this.sharedConflict;
                         this.sharedConflict = null;
                     }
                 } else {
                     if (this.restarter.shouldRestart()) {
                         // Reached bound on number of conflicts
                         // Force a restart
                         cancelUntil(this.rootLevel);
                         return Lbool.UNDEFINED;
                     }
                     if (this.needToReduceDB) {
                         reduceDB();
                         this.needToReduceDB = false;
                         // Runtime.getRuntime().gc();
                     }
                     if (this.sharedConflict == null) {
                         // New variable decision
                         this.stats.decisions++;
                         int p = this.order.select();
                         if (p == ILits.UNDEFINED) {
                             confl = preventTheSameDecisionsToBeMade();
                             this.lastConflictMeansUnsat = false;
                         } else {
                             assert p > 1;
                             this.slistener.assuming(toDimacs(p));
                             boolean ret = assume(p);
                             assert ret;
                         }
                     } else {
                         // listener called ISolverService.backtrack()
                         confl = this.sharedConflict;
                         this.sharedConflict = null;
                     }
                 }
             }
             if (confl != null) {
                 // un conflit apparait
                 this.stats.conflicts++;
                 this.slistener.conflictFound(confl, decisionLevel(),
                         this.trail.size());
                 this.conflictCount.newConflict();

                 if (decisionLevel() == this.rootLevel) {
                     if (this.lastConflictMeansUnsat) {
                         // conflict at root level, the formula is inconsistent
                         this.unsatExplanationInTermsOfAssumptions = analyzeFinalConflictInTermsOfAssumptions(
                                 confl, assumps, ILits.UNDEFINED);
                         return Lbool.FALSE;
                     }
                     return Lbool.UNDEFINED;
                 }
                 int conflictTrailLevel = this.trail.size();
                 // analyze conflict
                 try {
                     analyze(confl, this.analysisResult);
                 } catch (TimeoutException e) {
                     return Lbool.UNDEFINED;
                 }
                 assert this.analysisResult.backtrackLevel < decisionLevel();
                 backjumpLevel = Math.max(this.analysisResult.backtrackLevel,
                         this.rootLevel);
                 this.slistener.backjump(backjumpLevel);
                 cancelUntil(backjumpLevel);
                 if (backjumpLevel == this.rootLevel) {
                     this.restarter.onBackjumpToRootLevel();
                 }
                 assert decisionLevel() >= this.rootLevel
                         && decisionLevel() >= this.analysisResult.backtrackLevel;
                 if (this.analysisResult.reason == null) {
                     return Lbool.FALSE;
                 }
                 record(this.analysisResult.reason);
                 this.restarter.newLearnedClause(this.analysisResult.reason,
                         conflictTrailLevel);
                 this.analysisResult.reason = null;
                 decayActivities();
             }
         } while (this.undertimeout);
         return Lbool.UNDEFINED; // timeout occured
     }

     private Constr preventTheSameDecisionsToBeMade() {
         IVecInt clause = new VecInt(nVars());
         int p;
         for (int i = this.trail.size() - 1; i >= this.rootLevel; i--) {
             p = this.trail.get(i);
             if (this.voc.getReason(p) == null) {
                 clause.push(p ^ 1);
             }
         }
         return this.dsfactory.createUnregisteredClause(clause);
     }

     protected void analyzeAtRootLevel(Constr conflict) {
     }

     private final IVecInt implied = new VecInt();
     private final IVecInt decisions = new VecInt();

     private int[] fullmodel;

     /**
      *
      */
     void modelFound() {
         IVecInt tempmodel = new VecInt(nVars());
         this.userbooleanmodel = new boolean[realNumberOfVariables()];
         this.fullmodel = null;
         for (int i = 1; i <= nVars(); i++) {
             if (this.voc.belongsToPool(i)) {
                 int p = this.voc.getFromPool(i);
                 if (!this.voc.isUnassigned(p)) {
                     tempmodel.push(this.voc.isSatisfied(p) ? i : -i);
                     this.userbooleanmodel[i - 1] = this.voc.isSatisfied(p);
                     if (this.voc.getReason(p) == null && voc.getLevel(p) > 0) {
                         this.decisions.push(tempmodel.last());
                     } else {
                         this.implied.push(tempmodel.last());
                     }
                 }
             }
         }
         this.model = new int[tempmodel.size()];
         tempmodel.copyTo(this.model);
         if (realNumberOfVariables() > nVars()) {
             for (int i = nVars() + 1; i <= realNumberOfVariables(); i++) {
                 if (this.voc.belongsToPool(i)) {
                     int p = this.voc.getFromPool(i);
                     if (!this.voc.isUnassigned(p)) {
                         tempmodel.push(this.voc.isSatisfied(p) ? i : -i);
                         this.userbooleanmodel[i - 1] = this.voc.isSatisfied(p);
                         if (this.voc.getReason(p) == null) {
                             this.decisions.push(tempmodel.last());
                         } else {
                             this.implied.push(tempmodel.last());
                         }
                     }
                 }
             }
             this.fullmodel = new int[tempmodel.size()];
             tempmodel.moveTo(this.fullmodel);
         } else {
             this.fullmodel = this.model;
         }
     }

     /**
      * Forget a variable in the formula by falsifying both its positive and
      * negative literals.
      *
      * @param var
      *            a variable
      * @return a conflicting constraint resulting from the disparition of those
      *         literals.
      */
     private Constr forget(int var) {
         boolean satisfied = this.voc.isSatisfied(toInternal(var));
         this.voc.forgets(var);
         Constr confl;
         if (satisfied) {
             confl = reduceClausesForFalsifiedLiteral(LiteralsUtils
                     .toInternal(-var));
         } else {
             confl = reduceClausesForFalsifiedLiteral(LiteralsUtils
                     .toInternal(var));
         }
         return confl;
     }

     /**
      * Assume literal p and perform unit propagation
      *
      * @param p
      *            a literal
      * @return true if no conflict is reached, false if a conflict is found.
      */
     private boolean setAndPropagate(int p) {
         if (voc.isUnassigned(p)) {
             assert !trail.contains(p);
             assert !trail.contains(neg(p));
             return assume(p) && propagate() == null;
         }
         return voc.isSatisfied(p);
     }

     private int[] prime;

     public int[] primeImplicant() {
         assert this.qhead == this.trail.size() + this.learnedLiterals.size();
         if (this.learnedLiterals.size() > 0) {
             this.qhead = trail.size();
         }
         System.out.printf("%s implied: %d, decision: %d %n", getLogPrefix(),
                 implied.size(), decisions.size());
         this.prime = new int[realNumberOfVariables() + 1];
         int p, d;
         for (int i = 0; i < this.prime.length; i++) {
             this.prime[i] = 0;
         }
         boolean noproblem;
         for (IteratorInt it = this.implied.iterator(); it.hasNext();) {
             d = it.next();
             p = toInternal(d);
             this.prime[Math.abs(d)] = d;
             noproblem = setAndPropagate(p);
             assert noproblem;
         }
         boolean canBeRemoved;
         int rightlevel;
         int removed = 0;
         int propagated = 0;
         int tested = 0;
         int l2propagation = 0;

         for (int i = 0; i < this.decisions.size(); i++) {
             d = this.decisions.get(i);
             assert !this.voc.isFalsified(toInternal(d));
             if (this.voc.isSatisfied(toInternal(d))) {
                 // d has been propagated
                 this.prime[Math.abs(d)] = d;
                 propagated++;
             } else if (setAndPropagate(toInternal(-d))) {
                 canBeRemoved = true;
                 tested++;
                 rightlevel = currentDecisionLevel();
                 for (int j = i + 1; j < this.decisions.size(); j++) {
                     l2propagation++;
                     if (!setAndPropagate(toInternal(this.decisions.get(j)))) {
                         canBeRemoved = false;
                         break;
                     }
                 }
                 cancelUntil(rightlevel);
                 if (canBeRemoved) {
                     // it is not a necessary literal
                     forget(Math.abs(d));
                     IConstr confl = propagate();
                     assert confl == null;
                     removed++;
                 } else {
                     this.prime[Math.abs(d)] = d;
                     cancel();
                     assert voc.isUnassigned(toInternal(d));
                     noproblem = setAndPropagate(toInternal(d));
                     assert noproblem;
                 }
             } else {
                 // conflict, literal is necessary
                 this.prime[Math.abs(d)] = d;
                 cancel();
                 noproblem = setAndPropagate(toInternal(d));
                 assert noproblem;
             }
         }
         cancelUntil(0);
         int[] implicant = new int[this.prime.length - removed - 1];
         int index = 0;
         for (int i : this.prime) {
             if (i != 0) {
                 implicant[index++] = i;
             }
         }
         if (isVerbose()) {
             System.out.printf("%s prime implicant computation statistics%n",
                     getLogPrefix());
             System.out
                     .printf("%s implied: %d, decision: %d (removed %d, tested %d, propagated %d), l2 propagation:%d%n",
                             getLogPrefix(), implied.size(), decisions.size(),
                             removed, tested, propagated, l2propagation);
         }
         return implicant;
     }

     public boolean primeImplicant(int p) {
         if (p == 0 || Math.abs(p) > realNumberOfVariables()) {
             throw new IllegalArgumentException(
                     "Use a valid Dimacs var id as argument!"); //$NON-NLS-1$
         }
         if (this.prime == null) {
             throw new UnsupportedOperationException(
                     "Call the primeImplicant method first!!!"); //$NON-NLS-1$
         }
         return this.prime[Math.abs(p)] == p;
     }

     public boolean model(int var) {
         if (var <= 0 || var > realNumberOfVariables()) {
             throw new IllegalArgumentException(
                     "Use a valid Dimacs var id as argument!"); //$NON-NLS-1$
         }
         if (this.userbooleanmodel == null) {
             throw new UnsupportedOperationException(
                     "Call the solve method first!!!"); //$NON-NLS-1$
         }
         return this.userbooleanmodel[var - 1];
     }

     public void clearLearntClauses() {
         for (Iterator<Constr> iterator = this.learnts.iterator(); iterator
                 .hasNext();) {
             iterator.next().remove(this);
         }
         this.learnts.clear();
         this.learnedLiterals.clear();
     }

     protected final void reduceDB() {
         this.stats.reduceddb++;
         this.slistener.cleaning();
         this.learnedConstraintsDeletionStrategy.reduce(this.learnts);
         System.gc();
     }

     /**
      * @param learnts
      */
     protected void sortOnActivity() {
         this.learnts.sort(this.comparator);
     }

     /**
      *
      */
     protected void decayActivities() {
         this.order.varDecayActivity();
         claDecayActivity();
     }

     /**
      *
      */
     private void claDecayActivity() {
         this.claInc *= this.claDecay;
     }

     /**
      * @return true iff the set of constraints is satisfiable, else false.
      */
     public boolean isSatisfiable() throws TimeoutException {
         return isSatisfiable(VecInt.EMPTY);
     }

     /**
      * @return true iff the set of constraints is satisfiable, else false.
      */
     public boolean isSatisfiable(boolean global) throws TimeoutException {
         return isSatisfiable(VecInt.EMPTY, global);
     }

     private double timebegin = 0;

     private boolean needToReduceDB;

     private ConflictTimerContainer conflictCount;

     private transient Timer timer;

     public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
         return isSatisfiable(assumps, false);
     }

     public final LearnedConstraintsDeletionStrategy fixedSize(final int maxsize) {
         return new LearnedConstraintsDeletionStrategy() {

             private static final long serialVersionUID = 1L;
             private final ConflictTimer aTimer = new ConflictTimerAdapter(
                     maxsize) {

                 private static final long serialVersionUID = 1L;

                 @Override
                 public void run() {
                     Solver.this.needToReduceDB = true;
                 }
             };

             public void reduce(IVec<Constr> learnedConstrs) {
                 int i, j, k;
                 for (i = j = k = 0; i < Solver.this.learnts.size()
                         && Solver.this.learnts.size() - k > maxsize; i++) {
                     Constr c = Solver.this.learnts.get(i);
                     if (c.locked() || c.size() == 2) {
                         Solver.this.learnts
                                 .set(j++, Solver.this.learnts.get(i));
                     } else {
                         c.remove(Solver.this);
                         k++;
                     }
                 }
                 for (; i < Solver.this.learnts.size(); i++) {
                     Solver.this.learnts.set(j++, Solver.this.learnts.get(i));
                 }
                 if (Solver.this.verbose) {
                     Solver.this.out.log(getLogPrefix()
                             + "cleaning " + (Solver.this.learnts.size() - j) //$NON-NLS-1$
                             + " clauses out of " + Solver.this.learnts.size()); //$NON-NLS-1$
                     // out.flush();
                 }
                 Solver.this.learnts.shrinkTo(j);
             }

             public void onConflictAnalysis(Constr reason) {
                 // TODO Auto-generated method stub

             }

             public void onClauseLearning(Constr outLearnt) {
                 // TODO Auto-generated method stub

             }

             @Override
             public String toString() {
                 return "Fixed size (" + maxsize
                         + ") learned constraints deletion strategy";
             }

             public void init() {
             }

             public ConflictTimer getTimer() {
                 return this.aTimer;
             }

             public void onPropagation(Constr from) {
                 // TODO Auto-generated method stub

             }
         };
     }

     private LearnedConstraintsDeletionStrategy activityBased(
             final ConflictTimer timer) {
         return new LearnedConstraintsDeletionStrategy() {

             private static final long serialVersionUID = 1L;

             private final ConflictTimer freeMem = timer;

             public void reduce(IVec<Constr> learnedConstrs) {
                 sortOnActivity();
                 int i, j;
                 for (i = j = 0; i < Solver.this.learnts.size() / 2; i++) {
                     Constr c = Solver.this.learnts.get(i);
                     if (c.locked() || c.size() == 2) {
                         Solver.this.learnts
                                 .set(j++, Solver.this.learnts.get(i));
                     } else {
                         c.remove(Solver.this);
                     }
                 }
                 for (; i < Solver.this.learnts.size(); i++) {
                     Solver.this.learnts.set(j++, Solver.this.learnts.get(i));
                 }
                 if (Solver.this.verbose) {
                     Solver.this.out.log(getLogPrefix()
                             + "cleaning " + (Solver.this.learnts.size() - j) //$NON-NLS-1$
                             + " clauses out of " + Solver.this.learnts.size()); //$NON-NLS-1$
                     // out.flush();
                 }
                 Solver.this.learnts.shrinkTo(j);
             }

             public ConflictTimer getTimer() {
                 return this.freeMem;
             }

             @Override
             public String toString() {
                 return "Memory based learned constraints deletion strategy";
             }

             public void init() {
                 // do nothing
             }

             public void onClauseLearning(Constr constr) {
                 // do nothing

             }

             public void onConflictAnalysis(Constr reason) {
                 if (reason.learnt()) {
                     claBumpActivity(reason);
                 }
             }

             public void onPropagation(Constr from) {
                 // do nothing
             }
         };
     }

     private final ConflictTimer memoryTimer = new ConflictTimerAdapter(500) {
         private static final long serialVersionUID = 1L;
         final long memorybound = Runtime.getRuntime().freeMemory() / 10;

         @Override
         public void run() {
             long freemem = Runtime.getRuntime().freeMemory();
             // System.out.println("c Free memory "+freemem);
             if (freemem < this.memorybound) {
                 // Reduce the set of learnt clauses
                 Solver.this.needToReduceDB = true;
             }
         }
     };

     /**
      * @since 2.1
      */
     public final LearnedConstraintsDeletionStrategy memory_based = activityBased(this.memoryTimer);

     private class GlucoseLCDS implements LearnedConstraintsDeletionStrategy {

         private static final long serialVersionUID = 1L;
         private int[] flags = new int[0];
         private int flag = 0;
         // private int wall = 0;

         private final ConflictTimer clauseManagement;

         GlucoseLCDS(ConflictTimer timer) {
             this.clauseManagement = timer;
         }

         public void reduce(IVec<Constr> learnedConstrs) {
             sortOnActivity();
             int i, j;
             for (i = j = learnedConstrs.size() / 2; i < learnedConstrs.size(); i++) {
                 Constr c = learnedConstrs.get(i);
                 if (c.locked() || c.getActivity() <= 2.0) {
                     learnedConstrs.set(j++, Solver.this.learnts.get(i));
                 } else {
                     c.remove(Solver.this);
                 }
             }
             if (Solver.this.verbose) {
                 Solver.this.out
                         .log(getLogPrefix()
                                 + "cleaning " + (learnedConstrs.size() - j) //$NON-NLS-1$
                                 + " clauses out of " + learnedConstrs.size() + " with flag " + this.flag + "/" + Solver.this.stats.conflicts); //$NON-NLS-1$ //$NON-NLS-2$
                 // out.flush();
             }
             Solver.this.learnts.shrinkTo(j);

         }

         public ConflictTimer getTimer() {
             return this.clauseManagement;
         }

         @Override
         public String toString() {
             return "Glucose learned constraints deletion strategy";
         }

         public void init() {
             final int howmany = Solver.this.voc.nVars();
             // wall = constrs.size() > 10000 ? constrs.size() : 10000;
             if (this.flags.length <= howmany) {
                 this.flags = new int[howmany + 1];
             }
             this.flag = 0;
             this.clauseManagement.reset();
         }

         public void onClauseLearning(Constr constr) {
             int nblevel = computeLBD(constr);
             constr.incActivity(nblevel);
         }

         protected int computeLBD(Constr constr) {
             int nblevel = 1;
             this.flag++;
             int currentLevel;
             for (int i = 1; i < constr.size(); i++) {
                 currentLevel = Solver.this.voc.getLevel(constr.get(i));
                 if (this.flags[currentLevel] != this.flag) {
                     this.flags[currentLevel] = this.flag;
                     nblevel++;
                 }
             }
             return nblevel;
         }

         public void onConflictAnalysis(Constr reason) {

         }

         public void onPropagation(Constr from) {

         }
     }

     private class Glucose2LCDS extends GlucoseLCDS {

         /**
 		 *
 		 */
         private static final long serialVersionUID = 1L;

         Glucose2LCDS(ConflictTimer timer) {
             super(timer);
         }

         @Override
         public String toString() {
             return "Glucose 2 learned constraints deletion strategy";
         }

         @Override
         public void onPropagation(Constr from) {
             if (from.getActivity() > 2.0) {
                 int nblevel = computeLBD(from);
                 if (nblevel < from.getActivity()) {
                     Solver.this.stats.updateLBD++;
                     from.setActivity(nblevel);
                 }
             }
         }

     }

     private final ConflictTimer lbdTimer = new ConflictTimerAdapter(1000) {
         private static final long serialVersionUID = 1L;
         private int nbconflict = 0;
         private static final int MAX_CLAUSE = 5000;
         private static final int INC_CLAUSE = 1000;
         private int nextbound = MAX_CLAUSE;

         @Override
         public void run() {
             this.nbconflict += bound();
             if (this.nbconflict >= this.nextbound) {
                 this.nextbound += INC_CLAUSE;
                 // if (nextbound > wall) {
                 // nextbound = wall;
                 // }
                 this.nbconflict = 0;
                 Solver.this.needToReduceDB = true;
             }
         }

         @Override
         public void reset() {
             super.reset();
             this.nextbound = MAX_CLAUSE;
             if (this.nbconflict >= this.nextbound) {
                 this.nbconflict = 0;
                 Solver.this.needToReduceDB = true;
             }
         }
     };

     /**
      * @since 2.1
      */
     public final LearnedConstraintsDeletionStrategy glucose = new Glucose2LCDS(
             this.lbdTimer);

     protected LearnedConstraintsDeletionStrategy learnedConstraintsDeletionStrategy = this.glucose;

     /*
      * (non-Javadoc)
      *
      * @see
      * org.sat4j.minisat.core.ICDCL#setLearnedConstraintsDeletionStrategy(org
      * .sat4j.minisat.core.Solver.LearnedConstraintsDeletionStrategy)
      */
     public void setLearnedConstraintsDeletionStrategy(
             LearnedConstraintsDeletionStrategy lcds) {
         if (this.conflictCount != null) {
             this.conflictCount.add(lcds.getTimer());
             assert this.learnedConstraintsDeletionStrategy != null;
             this.conflictCount.remove(this.learnedConstraintsDeletionStrategy
                     .getTimer());
         }
         this.learnedConstraintsDeletionStrategy = lcds;
     }

     private boolean lastConflictMeansUnsat;

     public boolean isSatisfiable(IVecInt assumps, boolean global)
             throws TimeoutException {
         Lbool status = Lbool.UNDEFINED;
         boolean alreadylaunched = this.conflictCount != null;
         final int howmany = this.voc.nVars();
         if (this.mseen.length <= howmany) {
             this.mseen = new boolean[howmany + 1];
         }
         this.trail.ensure(howmany);
         this.trailLim.ensure(howmany);
         this.learnedLiterals.ensure(howmany);
         this.decisions.clear();
         this.implied.clear();
         this.slistener.init(this);
         this.slistener.start();
         this.model = null; // forget about previous model
         this.userbooleanmodel = null;
         this.prime = null;
         this.unsatExplanationInTermsOfAssumptions = null;
         if (!alreadylaunched || !this.keepHot) {
             this.order.init();
         }
         this.learnedConstraintsDeletionStrategy.init();
         int learnedLiteralsLimit = this.trail.size();

         // Fix for Bug SAT37
         this.qhead = 0;
         // Apply undos on unit literals because they are getting propagated
         // again now that qhead is 0.
         for (int i = learnedLiteralsLimit - 1; i >= 0; i--) {
             int p = this.trail.get(i);
             IVec<Undoable> undos = this.voc.undos(p);
             assert undos != null;
             for (int size = undos.size(); size > 0; size--) {
                 undos.last().undo(p);
                 undos.pop();
             }
         }
         // push previously learned literals
         for (IteratorInt iterator = this.learnedLiterals.iterator(); iterator
                 .hasNext();) {
             enqueue(iterator.next());
         }

         // propagate constraints
         Constr confl = propagate();
         if (confl != null) {
             analyzeAtRootLevel(confl);
             this.slistener.conflictFound(confl, 0, 0);
             this.slistener.end(Lbool.FALSE);
             cancelUntil(0);
             cancelLearntLiterals(learnedLiteralsLimit);
             return false;
         }

         // push incremental assumptions
         for (IteratorInt iterator = assumps.iterator(); iterator.hasNext();) {
             int assump = iterator.next();
             int p = this.voc.getFromPool(assump);
             if (!this.voc.isSatisfied(p) && !assume(p)
                     || (confl = propagate()) != null) {
                 if (confl == null) {
                     this.slistener.conflictFound(p);
                     this.unsatExplanationInTermsOfAssumptions = analyzeFinalConflictInTermsOfAssumptions(
                             null, assumps, p);
                     this.unsatExplanationInTermsOfAssumptions.push(assump);
                 } else {
                     this.slistener.conflictFound(confl, decisionLevel(),
                             this.trail.size());
                     this.unsatExplanationInTermsOfAssumptions = analyzeFinalConflictInTermsOfAssumptions(
                             confl, assumps, ILits.UNDEFINED);
                 }

                 this.slistener.end(Lbool.FALSE);
                 cancelUntil(0);
                 cancelLearntLiterals(learnedLiteralsLimit);
                 return false;
             }
         }
         this.rootLevel = decisionLevel();
         // moved initialization here if new literals are added in the
         // assumptions.
         if (!alreadylaunched || !this.keepHot) {
             this.order.init(); // duplicated on purpose
         }
         this.learner.init();

         if (!alreadylaunched) {
             this.conflictCount = new ConflictTimerContainer();
             this.conflictCount.add(this.restarter);
             this.conflictCount.add(this.learnedConstraintsDeletionStrategy
                     .getTimer());
         }
         boolean firstTimeGlobal = false;
         if (this.timeBasedTimeout) {
             if (!global || this.timer == null) {
                 firstTimeGlobal = true;
                 this.undertimeout = true;
                 TimerTask stopMe = new TimerTask() {
                     @Override
                     public void run() {
                         Solver.this.undertimeout = false;
                     }
                 };
                 this.timer = new Timer(true);
                 this.timer.schedule(stopMe, this.timeout);

             }
         } else {
             if (!global || !alreadylaunched) {
                 firstTimeGlobal = true;
                 this.undertimeout = true;
                 ConflictTimer conflictTimeout = new ConflictTimerAdapter(
                         (int) this.timeout) {
                     private static final long serialVersionUID = 1L;

                     @Override
                     public void run() {
                         Solver.this.undertimeout = false;
                     }
                 };
                 this.conflictCount.add(conflictTimeout);
             }
         }
         if (!global || firstTimeGlobal) {
             this.restarter.init(this.params, this.stats);
             this.timebegin = System.currentTimeMillis();
         }
         this.needToReduceDB = false;
         // this is used to allow the solver to be incomplete,
         // when using a heuristics limited to a subset of variables
         this.lastConflictMeansUnsat = true;
         // Solve
         while (status == Lbool.UNDEFINED && this.undertimeout
                 && this.lastConflictMeansUnsat) {
             status = search(assumps);
             if (status == Lbool.UNDEFINED) {
                 this.restarter.onRestart();
                 this.slistener.restarting();
             }
         }

         cancelUntil(0);
         cancelLearntLiterals(learnedLiteralsLimit);
         if (!global && this.timeBasedTimeout && this.timer != null) {
             this.timer.cancel();
             this.timer = null;
         }
         this.slistener.end(status);
         if (!this.undertimeout) {
             String message = " Timeout (" + this.timeout
                     + (this.timeBasedTimeout ? "s" : " conflicts")
                     + ") exceeded";
             throw new TimeoutException(message);
         }
         if (status == Lbool.UNDEFINED && !this.lastConflictMeansUnsat) {
             throw new TimeoutException("Cannot decide the satisfiability");
         }
         // When using a search enumerator (to compute all models)
         // the final answer is FALSE, however we are aware of at least one model
         // (the last one)
         return model != null;
     }

     public void printInfos(PrintWriter out) {
         printInfos(out, prefix);
     }

     public void printInfos(PrintWriter out, String prefix) {
         out.print(prefix);
         out.println("constraints type ");
         long total = 0;
         for (Map.Entry<String, Counter> entry : this.constrTypes.entrySet()) {
             out.println(prefix + entry.getKey() + " => " + entry.getValue());
             total += entry.getValue().getValue();
         }
         out.print(prefix);
         out.print(total);
         out.println(" constraints processed.");
     }

     /**
      * @since 2.1
      */
     public void printLearntClausesInfos(PrintWriter out, String prefix) {
         Map<String, Counter> learntTypes = new HashMap<String, Counter>();
         for (Iterator<Constr> it = this.learnts.iterator(); it.hasNext();) {
             String type = it.next().getClass().getName();
             Counter count = learntTypes.get(type);
             if (count == null) {
                 learntTypes.put(type, new Counter());
             } else {
                 count.inc();
             }
         }
         out.print(prefix);
         out.println("learnt constraints type ");
         for (Map.Entry<String, Counter> entry : learntTypes.entrySet()) {
             out.println(prefix + entry.getKey() + " => " + entry.getValue());
         }
     }

     public SolverStats getStats() {
         return this.stats;
     }

     /**
      *
      * @param myStats
      * @since 2.2
      */
     protected void initStats(SolverStats myStats) {
         this.stats = myStats;
     }

     /*
      * (non-Javadoc)
      *
      * @see org.sat4j.minisat.core.ICDCL#getOrder()
      */
     public IOrder getOrder() {
         return this.order;
     }

     /*
      * (non-Javadoc)
      *
      * @see org.sat4j.minisat.core.ICDCL#setOrder(org.sat4j.minisat.core.IOrder)
      */
     public void setOrder(IOrder h) {
         this.order = h;
         this.order.setLits(this.voc);
     }

     public ILits getVocabulary() {
         return this.voc;
     }

     public void reset() {
         if (this.timer != null) {
             this.timer.cancel();
             this.timer = null;
         }
         this.trail.clear();
         this.trailLim.clear();
         this.qhead = 0;
         for (Iterator<Constr> iterator = this.constrs.iterator(); iterator
                 .hasNext();) {
             iterator.next().remove(this);
         }
         this.constrs.clear();
         clearLearntClauses();
         this.voc.resetPool();
         this.dsfactory.reset();
         this.stats.reset();
         this.constrTypes.clear();
     }

     public int nVars() {
         if (this.declaredMaxVarId == 0) {
             return this.voc.nVars();
         }
         return this.declaredMaxVarId;
     }

     /**
      * @param constr
      *            a constraint implementing the Constr interface.
      * @return a reference to the constraint for external use.
      */
     protected IConstr addConstr(Constr constr) {
         if (constr == null) {
             Counter count = this.constrTypes
                     .get("ignored satisfied constraints");
             if (count == null) {
                 this.constrTypes.put("ignored satisfied constraints",
                         new Counter());
             } else {
                 count.inc();
             }
         } else {
             this.constrs.push(constr);
             String type = constr.getClass().getName();
             Counter count = this.constrTypes.get(type);
             if (count == null) {
                 this.constrTypes.put(type, new Counter());
             } else {
                 count.inc();
             }
         }
         return constr;
     }

     public DataStructureFactory getDSFactory() {
         return this.dsfactory;
     }

     public IVecInt getOutLearnt() {
         return this.moutLearnt;
     }

     /**
      * returns the ith constraint in the solver.
      *
      * @param i
      *            the constraint number (begins at 0)
      * @return the ith constraint
      */
     public IConstr getIthConstr(int i) {
         return this.constrs.get(i);
     }

     /*
      * (non-Javadoc)
      *
      * @see org.sat4j.specs.ISolver#printStat(java.io.PrintStream,
      * java.lang.String)
      */
     public void printStat(PrintStream out, String prefix) {
         printStat(new PrintWriter(out, true), prefix);
     }

     public void printStat(PrintWriter out) {
         printStat(out, prefix);
     }

     public void printStat(PrintWriter out, String prefix) {
         this.stats.printStat(out, prefix);
         double cputime = (System.currentTimeMillis() - this.timebegin) / 1000;
         out.println(prefix
                 + "speed (assignments/second)\t: " + this.stats.propagations //$NON-NLS-1$
                 / cputime);
         this.order.printStat(out, prefix);
         printLearntClausesInfos(out, prefix);
     }

     /*
      * (non-Javadoc)
      *
      * @see java.lang.Object#toString()
      */
     public String toString(String prefix) {
         StringBuffer stb = new StringBuffer();
         Object[] objs = { this.dsfactory, this.learner, this.params,
                 this.order, this.simplifier, this.restarter,
                 this.learnedConstraintsDeletionStrategy };
         stb.append(prefix);
         stb.append("--- Begin Solver configuration ---"); //$NON-NLS-1$
         stb.append("\n"); //$NON-NLS-1$
         for (Object o : objs) {
             stb.append(prefix);
             stb.append(o.toString());
             stb.append("\n"); //$NON-NLS-1$
         }
         stb.append(prefix);
         stb.append("timeout=");
         if (this.timeBasedTimeout) {
             stb.append(this.timeout / 1000);
             stb.append("s\n");
         } else {
             stb.append(this.timeout);
             stb.append(" conflicts\n");
         }
         stb.append(prefix);
         stb.append("DB Simplification allowed=");
         stb.append(this.isDBSimplificationAllowed);
         stb.append("\n");
         stb.append(prefix);
         if (isSolverKeptHot()) {
             stb.append("Heuristics kept accross calls (keep the solver \"hot\")\n");
             stb.append(prefix);
         }
         stb.append("Listener: ");
         stb.append(slistener);
         stb.append("\n");
         stb.append(prefix);
         stb.append("--- End Solver configuration ---"); //$NON-NLS-1$
         return stb.toString();
     }

     /*
      * (non-Javadoc)
      *
      * @see java.lang.Object#toString()
      */
     @Override
     public String toString() {
         return toString(""); //$NON-NLS-1$
     }

     public int getTimeout() {
         return (int) (this.timeBasedTimeout ? this.timeout / 1000
                 : this.timeout);
     }

     /**
      * @since 2.1
      */
     public long getTimeoutMs() {
         if (!this.timeBasedTimeout) {
             throw new UnsupportedOperationException(
                     "The timeout is given in number of conflicts!");
         }
         return this.timeout;
     }

     public void setExpectedNumberOfClauses(int nb) {
         this.constrs.ensure(nb);
     }

     public Map<String, Number> getStat() {
         return this.stats.toMap();
     }

     public int[] findModel() throws TimeoutException {
         if (isSatisfiable()) {
             return model();
         }
         // DLB findbugs ok
         // A zero length array would mean that the formula is a tautology.
         return null;
     }

     public int[] findModel(IVecInt assumps) throws TimeoutException {
         if (isSatisfiable(assumps)) {
             return model();
         }
         // DLB findbugs ok
         // A zero length array would mean that the formula is a tautology.
         return null;
     }

     public boolean isDBSimplificationAllowed() {
         return this.isDBSimplificationAllowed;
     }

     public void setDBSimplificationAllowed(boolean status) {
         this.isDBSimplificationAllowed = status;
     }

     /**
      * @since 2.1
      */
     public int nextFreeVarId(boolean reserve) {
         return this.voc.nextFreeVarId(reserve);
     }

     /**
      * @since 2.1
      */
     public IConstr addBlockingClause(IVecInt literals)
             throws ContradictionException {
         return addClause(literals);
     }

     /**
      * @since 2.1
      */
     public void unset(int p) {
         // the literal might already have been
         // removed from the trail.
         if (this.voc.isUnassigned(p) || this.trail.isEmpty()) {
             return;
         }
         int current = this.trail.last();
         while (current != p) {
             undoOne();
             if (this.trail.isEmpty()) {
                 return;
             }
             current = this.trail.last();
         }
         undoOne();
         this.qhead = this.trail.size();
     }

     /**
      * @since 2.2
      */
     public void setLogPrefix(String prefix) {
         this.prefix = prefix;
     }

     /**
      * @since 2.2
      */
     public String getLogPrefix() {
         return this.prefix;
     }

     /**
      * @since 2.2
      */
     public IVecInt unsatExplanation() {
         IVecInt copy = new VecInt(
                 this.unsatExplanationInTermsOfAssumptions.size());
         this.unsatExplanationInTermsOfAssumptions.copyTo(copy);
         return copy;
     }

     /**
      * @since 2.3.1
      */
     public int[] modelWithInternalVariables() {
         if (this.model == null) {
             throw new UnsupportedOperationException(
                     "Call the solve method first!!!"); //$NON-NLS-1$
         }
         int[] nmodel;
         if (nVars() == realNumberOfVariables()) {
             nmodel = new int[this.model.length];
             System.arraycopy(this.model, 0, nmodel, 0, nmodel.length);
         } else {
             nmodel = new int[this.fullmodel.length];
             System.arraycopy(this.fullmodel, 0, nmodel, 0, nmodel.length);
         }

         return nmodel;
     }

     /**
      * @since 2.3.1
      */
     public int realNumberOfVariables() {
         return this.voc.nVars();
     }

     /**
      * @since 2.3.2
      */
     public void stop() {
         expireTimeout();
     }

     protected Constr sharedConflict;

     /**
      * @since 2.3.2
      */
     public void backtrack(int[] reason) {
         IVecInt clause = new VecInt(reason.length);
         for (int d : reason) {
             clause.push(LiteralsUtils.toInternal(d));
         }
         this.sharedConflict = this.dsfactory.createUnregisteredClause(clause);
         learn(this.sharedConflict);
     }

     /**
      * @since 2.3.2
      */
     public Lbool truthValue(int literal) {
         int p = LiteralsUtils.toInternal(literal);
         if (this.voc.isFalsified(p)) {
             return Lbool.FALSE;
         }
         if (this.voc.isSatisfied(p)) {
             return Lbool.TRUE;
         }
         return Lbool.UNDEFINED;
     }

     /**
      * @since 2.3.2
      */
     public int currentDecisionLevel() {
         return decisionLevel();
     }

     /**
      * @since 2.3.2
      */
     public int[] getLiteralsPropagatedAt(int decisionLevel) {
         throw new UnsupportedOperationException("Not implemented yet!");
     }

     /**
      * @since 2.3.2
      */
     public void suggestNextLiteralToBranchOn(int l) {
         throw new UnsupportedOperationException("Not implemented yet!");
     }

     protected boolean isNeedToReduceDB() {
         return this.needToReduceDB;
     }

     public void setNeedToReduceDB(boolean needToReduceDB) {
         this.needToReduceDB = needToReduceDB;
     }

     public void setLogger(ILogAble out) {
         this.out = out;
     }

     public ILogAble getLogger() {
         return this.out;
     }

     public double[] getVariableHeuristics() {
         return this.order.getVariableHeuristics();
     }

     public IVec<Constr> getLearnedConstraints() {
         return this.learnts;
     }

     /**
      * @since 2.3.2
      */
     public void setLearnedConstraintsDeletionStrategy(ConflictTimer timer,
             LearnedConstraintsEvaluationType evaluation) {
         if (this.conflictCount != null) {
             this.conflictCount.add(timer);
             this.conflictCount.remove(this.learnedConstraintsDeletionStrategy
                     .getTimer());
         }
         switch (evaluation) {
         case ACTIVITY:
             this.learnedConstraintsDeletionStrategy = activityBased(timer);
             break;
         case LBD:
             this.learnedConstraintsDeletionStrategy = new GlucoseLCDS(timer);
             break;
         case LBD2:
             this.learnedConstraintsDeletionStrategy = new Glucose2LCDS(timer);
             break;
         }
         if (this.conflictCount != null) {
             this.learnedConstraintsDeletionStrategy.init();
         }
     }

     /**
      * @since 2.3.2
      */
     public void setLearnedConstraintsDeletionStrategy(
             LearnedConstraintsEvaluationType evaluation) {
         ConflictTimer aTimer = this.learnedConstraintsDeletionStrategy
                 .getTimer();
         switch (evaluation) {
         case ACTIVITY:
             this.learnedConstraintsDeletionStrategy = activityBased(aTimer);
             break;
         case LBD:
             this.learnedConstraintsDeletionStrategy = new GlucoseLCDS(aTimer);
             break;
         case LBD2:
             this.learnedConstraintsDeletionStrategy = new Glucose2LCDS(aTimer);
             break;
         }
         if (this.conflictCount != null) {
             this.learnedConstraintsDeletionStrategy.init();
         }
     }

     public boolean isSolverKeptHot() {
         return this.keepHot;
     }

     public void setKeepSolverHot(boolean keepHot) {
         this.keepHot = keepHot;
     }

     public IConstr addClauseOnTheFly(int[] literals) {
         IVecInt clause = new VecInt(literals.length);
         for (int d : literals) {
             clause.push(LiteralsUtils.toInternal(d));
         }
         this.sharedConflict = this.dsfactory.createUnregisteredClause(clause);
         this.sharedConflict.register();
         addConstr(this.sharedConflict);
         IVecInt reason = new VecInt();
         this.sharedConflict.calcReasonOnTheFly(ILits.UNDEFINED, trail, reason);
         while (!trail.isEmpty() && !reason.contains(trail.last())) {
             undoOne();
             if (!trailLim.isEmpty() && trailLim.last() == trail.size()) {
                 trailLim.pop();
             }
         }
         return this.sharedConflict;
     }

     public ISolver getSolvingEngine() {
         return this;
     }

     /**
      *
      * @param literals
      */
     public IConstr addAtMostOnTheFly(int[] literals, int degree) {
         IVecInt clause = new VecInt(literals.length);
         for (int d : literals) {
             clause.push(LiteralsUtils.toInternal(-d));
         }
         IVecInt copy = new VecInt(clause.size());
         clause.copyTo(copy);
         this.sharedConflict = this.dsfactory
                 .createUnregisteredCardinalityConstraint(copy, literals.length
                         - degree);
         this.sharedConflict.register();
         addConstr(this.sharedConflict);
         // backtrack to the first decision level with a reason
         // for falsifying that constraint
         IVecInt reason = new VecInt();
         this.sharedConflict.calcReasonOnTheFly(ILits.UNDEFINED, trail, reason);
         while (!trail.isEmpty() && !reason.contains(trail.last())) {
             undoOne();
             if (!trailLim.isEmpty() && trailLim.last() == trail.size()) {
                 trailLim.pop();
             }
         }
         return this.sharedConflict;
     }
 }