/*******************************************************************************
    * 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++.
   * 
   * The reason simplification methods are coming from MiniSAT 1.14 released under 
   * the MIT license:
   * 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. 
   *******************************************************************************/
  package org.sat4j.minisat.core;
  
  import static org.sat4j.core.LiteralsUtils.toDimacs;
  import static org.sat4j.core.LiteralsUtils.var;
  
  import java.io.PrintStream;
  import java.io.PrintWriter;
  import java.io.Serializable;
  import java.lang.reflect.Field;
  import java.util.Comparator;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Timer;
  import java.util.TimerTask;
  
  import org.sat4j.core.Vec;
  import org.sat4j.core.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.ISolver;
  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 ISolver,
  		UnitPropagationListener, ActivityListener, Learner {
  
  	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;
  
  	/**
  	 * Set of original constraints.
  	 */
  	private final IVec<Constr> constrs = new Vec<Constr>(); // Constr
  
  	/**
  	 * Set of learned constraints.
 	 */
 	private final IVec<Constr> learnts = new Vec<Constr>(); // Clause
 
 	/**
 	 * incr?ment pour l'activit? des clauses.
 	 */
 	private double claInc = 1.0;
 
 	/**
 	 * decay factor pour l'activit? des clauses.
 	 */
 	private double claDecay = 1.0;
 
 	/**
 	 * Queue de propagation
 	 */
 	// head of the queue in trail ... (taken from MiniSAT 1.14)
 	private int qhead = 0;
 
 	// queue
 
 	/**
 	 * affectation en ordre chronologique
 	 */
 	protected final IVecInt trail = new VecInt(); // lit
 
 	// vector
 
 	/**
 	 * indice des s?parateurs des diff?rents niveau de d?cision dans trail
 	 */
 	protected final IVecInt trailLim = new VecInt(); // int
 
 	// vector
 
 	/**
 	 * S?pare les hypoth?ses incr?mentale et recherche
 	 */
 	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 final AssertingClauseGenerator analyzer;
 
 	private 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();
 
 	private 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 = true;
 
 	private String prefix = "c ";
 
 	protected IVecInt dimacs2internal(IVecInt in) {
 		__dimacs_out.clear();
 		__dimacs_out.ensure(in.size());
 		for (int i = 0; i < in.size(); i++) {
 			assert (in.get(i) != 0);
 			__dimacs_out.unsafePush(voc.getFromPool(in.get(i)));
 		}
 		return __dimacs_out;
 	}
 
 	/**
 	 * 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.
 	 * 
 	 * @param acg
 	 *            an asserting clause generator
 	 */
 
 	public Solver(AssertingClauseGenerator acg, LearningStrategy<D> learner,
 			D dsf, IOrder order, RestartStrategy restarter) {
 		this(acg, learner, dsf, new SearchParams(), order, restarter);
 	}
 
 	public Solver(AssertingClauseGenerator acg, LearningStrategy<D> learner,
 			D dsf, SearchParams params, IOrder order, RestartStrategy restarter) {
 		analyzer = acg;
 		this.learner = learner;
 		this.order = order;
 		this.params = params;
 		setDataStructureFactory(dsf);
 		this.restarter = restarter;
 	}
 
 	/**
 	 * Change the internal representation of the constraints. Note that the
 	 * heuristics must be changed prior to calling that method.
 	 * 
 	 * @param dsf
 	 *            the internal factory
 	 */
 	public final void setDataStructureFactory(D dsf) {
 		dsfactory = dsf;
 		dsfactory.setUnitPropagationListener(this);
 		dsfactory.setLearner(this);
 		voc = dsf.getVocabulary();
 		order.setLits(voc);
 	}
 
 	/**
 	 * @since 2.2
 	 */
 	public boolean isVerbose() {
 		return verbose;
 	}
 
 	/**
 	 * @param value
 	 * @since 2.2
 	 */
 	public void setVerbose(boolean value) {
 		verbose = value;
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public void setSearchListener(SearchListener sl) {
 		slistener = sl;
 	}
 
 	/**
 	 * @since 2.2
 	 */
 	public SearchListener getSearchListener() {
 		return slistener;
 	}
 
 	/**
 	 * @since 2.2
 	 */
 	public void setLearner(LearningStrategy<D> learner) {
 		this.learner = learner;
 	}
 
 	public void setTimeout(int t) {
 		timeout = t * 1000L;
 		timeBasedTimeout = true;
 	}
 
 	public void setTimeoutMs(long t) {
 		timeout = t;
 		timeBasedTimeout = true;
 	}
 
 	public void setTimeoutOnConflicts(int count) {
 		timeout = count;
 		timeBasedTimeout = false;
 	}
 
 	public void setSearchParams(SearchParams sp) {
 		params = sp;
 	}
 
 	public void setRestartStrategy(RestartStrategy restarter) {
 		this.restarter = restarter;
 	}
 
 	public void expireTimeout() {
 		undertimeout = false;
 	}
 
 	protected int nAssigns() {
 		return trail.size();
 	}
 
 	public int nConstraints() {
 		return constrs.size() + trail.size();
 	}
 
 	public void learn(Constr c) {
 		learnts.push(c);
 		c.setLearnt();
 		c.register();
 		stats.learnedclauses++;
 		switch (c.size()) {
 		case 2:
 			stats.learnedbinaryclauses++;
 			break;
 		case 3:
 			stats.learnedternaryclauses++;
 			break;
 		default:
 			// do nothing
 		}
 	}
 
 	public final int decisionLevel() {
 		return trailLim.size();
 	}
 
 	@Deprecated
 	public int newVar() {
 		int index = voc.nVars() + 1;
 		voc.ensurePool(index);
 		return index;
 	}
 
 	public int newVar(int howmany) {
 		voc.ensurePool(howmany);
 		return voc.nVars();
 	}
 
 	public IConstr addClause(IVecInt literals) throws ContradictionException {
 		IVecInt vlits = dimacs2internal(literals);
 		return addConstr(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);
 		constrs.remove(c);
 		clearLearntClauses();
 		String type = c.getClass().getName();
 		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 (constrs.last() != co) {
 			throw new IllegalArgumentException(
 					"Can only remove latest added constraint!!!"); //$NON-NLS-1$
 		}
 		Constr c = (Constr) co;
 		c.remove(this);
 		constrs.pop();
 		String type = c.getClass().getName();
 		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(dsfactory.createCardinalityConstraint(vlits, degree));
 	}
 
 	@SuppressWarnings("unchecked")
 	public boolean simplifyDB() {
 		// Simplifie la base de clauses apres la premiere propagation des
 		// clauses unitaires
 		IVec<Constr>[] cs = new IVec[] { constrs, 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 (model == null) {
 			throw new UnsupportedOperationException(
 					"Call the solve method first!!!"); //$NON-NLS-1$
 		}
 		int[] nmodel = new int[model.length];
 		System.arraycopy(model, 0, nmodel, 0, model.length);
 		return nmodel;
 	}
 
 	/**
 	 * Satisfait un litt?ral
 	 * 
 	 * @param p
 	 *            le litt?ral
 	 * @return true si tout se passe bien, false si un conflit appara?t.
 	 */
 	public boolean enqueue(int p) {
 		return enqueue(p, null);
 	}
 
 	/**
 	 * Put the literal on the queue of assignments to be done.
 	 * 
 	 * @param p
 	 *            the literal.
 	 * @param from
 	 *            the reason to propagate that literal, else null
 	 * @return true if the assignment can be made, false if a conflict is
 	 *         detected.
 	 */
 	public boolean enqueue(int p, Constr from) {
 		assert p > 1;
 		if (voc.isSatisfied(p)) {
 			// literal is already satisfied. Skipping.
 			return true;
 		}
 		if (voc.isFalsified(p)) {
 			// conflicting enqueued assignment
 			return false;
 		}
 		// new fact, store it
 		voc.satisfies(p);
 		voc.setLevel(p, decisionLevel());
 		voc.setReason(p, from);
 		trail.push(p);
 		return true;
 	}
 
 	private boolean[] mseen = new boolean[0];
 
 	private final IVecInt mpreason = new VecInt();
 
 	private final IVecInt moutLearnt = new VecInt();
 
 	public void analyze(Constr confl, Pair results) {
 		assert confl != null;
 
 		final boolean[] seen = mseen;
 		final IVecInt outLearnt = moutLearnt;
 		final IVecInt preason = mpreason;
 
 		outLearnt.clear();
 		assert outLearnt.size() == 0;
 		for (int i = 0; i < seen.length; i++) {
 			seen[i] = false;
 		}
 
 		analyzer.initAnalyze();
 		int p = ILits.UNDEFINED;
 
 		outLearnt.push(ILits.UNDEFINED);
 		// reserve de la place pour le litteral falsifie
 		int outBtlevel = 0;
 
 		do {
 			preason.clear();
 			assert confl != null;
 			confl.calcReason(p, preason);
 			learnedConstraintsDeletionStrategy.onConflictAnalysis(confl);
 			// Trace reason for p
 			for (int j = 0; j < preason.size(); j++) {
 				int q = preason.get(j);
 				order.updateVar(q);
 				if (!seen[q >> 1]) {
 					seen[q >> 1] = true;
 					if (voc.getLevel(q) == decisionLevel()) {
 						analyzer.onCurrentDecisionLevelLiteral(q);
 					} else if (voc.getLevel(q) > 0) {
 						// only literals assigned after decision level 0 part of
 						// the explanation
 						outLearnt.push(q ^ 1);
 						outBtlevel = Math.max(outBtlevel, voc.getLevel(q));
 					}
 				}
 			}
 
 			// select next reason to look at
 			do {
 				p = trail.last();
 				confl = 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 (analyzer.clauseNonAssertive(confl));
 
 		outLearnt.set(0, p ^ 1);
 		simplifier.simplify(outLearnt);
 
 		Constr c = dsfactory.createUnregisteredClause(outLearnt);
 		slistener.learn(c);
 		learnedConstraintsDeletionStrategy.onConflict(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;
 		}
 		final boolean[] seen = mseen;
 		final IVecInt outLearnt = moutLearnt;
 		final IVecInt preason = mpreason;
 
 		outLearnt.clear();
 		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) {
 			p = trail.last();
 			confl = voc.getReason(p);
 			undoOne();
 			if (trail.size() <= trailLim.last()) {
 				trailLim.pop();
 			}
 		}
 		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 (voc.getReason(q) == null && voc.getLevel(q) > 0) {
 						assert assumps.contains(toDimacs(q));
 						outLearnt.push(toDimacs(q));
 					}
 				}
 			}
 
 			// select next reason to look at
 			do {
 				p = trail.last();
 				confl = voc.getReason(p);
 				undoOne();
 				if (decisionLevel() > 0 && trail.size() <= trailLim.last()) {
 					trailLim.pop();
 				}
 			} while (trail.size() > 0 && decisionLevel() > 0
 					&& (!seen[p >> 1] || confl == null));
 		} while (decisionLevel() > 0);
 		return outLearnt;
 	}
 
 	interface ISimplifier extends Serializable {
 		void simplify(IVecInt 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"; //$NON-NLS-1$
 		}
 	};
 
 	private ISimplifier simplifier = NO_SIMPLIFICATION;
 
 	/**
 	 * Setup the reason simplification strategy. By default, there is no reason
 	 * simplification. NOTE THAT REASON SIMPLIFICATION DOES NOT WORK WITH
 	 * SPECIFIC DATA STRUCTURE FOR HANDLING BOTH BINARY AND TERNARY CLAUSES.
 	 * 
 	 * @param simp
 	 *            the name of the simplifier (one of NO_SIMPLIFICATION,
 	 *            SIMPLE_SIMPLIFICATION, EXPENSIVE_SIMPLIFICATION).
 	 */
 	public void setSimplifier(String simp) {
 		Field f;
 		try {
 			f = Solver.class.getDeclaredField(simp);
 			simplifier = (ISimplifier) f.get(this);
 		} catch (Exception e) {
 			e.printStackTrace();
 			simplifier = NO_SIMPLIFICATION;
 		}
 	}
 
 	/**
 	 * Setup the reason simplification strategy. By default, there is no reason
 	 * simplification. NOTE THAT REASON SIMPLIFICATION IS ONLY ALLOWED FOR WL
 	 * CLAUSAL data structures. USING REASON SIMPLIFICATION ON CB CLAUSES,
 	 * CARDINALITY CONSTRAINTS OR PB CONSTRAINTS MIGHT RESULT IN INCORRECT
 	 * RESULTS.
 	 * 
 	 * @param simp
 	 */
 	public void setSimplifier(ISimplifier simp) {
 		simplifier = simp;
 	}
 
 	// 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;
 		final boolean[] seen = mseen;
 		for (i = j = 1; i < conflictToReduce.size(); i++) {
 			IConstr r = voc.getReason(conflictToReduce.get(i));
 			if (r == null) {
 				conflictToReduce.moveTo(j++, i);
 			} else {
 				for (int k = 0; k < r.size(); k++)
 					if (voc.isFalsified(r.get(k)) && !seen[r.get(k) >> 1]
 							&& (voc.getLevel(r.get(k)) != 0)) {
 						conflictToReduce.moveTo(j++, i);
 						break;
 					}
 			}
 		}
 		conflictToReduce.shrink(i - j);
 		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)
 		analyzetoclear.clear();
 		conflictToReduce.copyTo(analyzetoclear);
 		for (i = 1, j = 1; i < conflictToReduce.size(); i++)
 			if (voc.getReason(conflictToReduce.get(i)) == null
 					|| !analyzeRemovable(conflictToReduce.get(i)))
 				conflictToReduce.moveTo(j++, i);
 		conflictToReduce.shrink(i - j);
 		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 voc.getReason(p) != null;
 		analyzestack.clear();
 		analyzestack.push(p);
 		final boolean[] seen = mseen;
 		int top = analyzetoclear.size();
 		while (analyzestack.size() > 0) {
 			int q = analyzestack.last();
 			assert voc.getReason(q) != null;
 			Constr c = voc.getReason(q);
 			analyzestack.pop();
 			for (int i = 0; i < c.size(); i++) {
 				int l = c.get(i);
 				if (voc.isFalsified(l) && !seen[var(l)] && voc.getLevel(l) != 0) {
 					if (voc.getReason(l) == null) {
 						for (int j = top; j < analyzetoclear.size(); j++)
 							seen[analyzetoclear.get(j) >> 1] = false;
 						analyzetoclear.shrink(analyzetoclear.size() - top);
 						return false;
 					}
 					seen[l >> 1] = true;
 					analyzestack.push(l);
 					analyzetoclear.push(l);
 				}
 			}
 		}
 
 		return true;
 	}
 
 	// END Minisat 1.14 cut and paste
 
 	/**
      * 
      */
 	protected void undoOne() {
 		// recupere le dernier litteral affecte
 		int p = trail.last();
 		assert p > 1;
 		assert voc.getLevel(p) >= 0;
 		int x = p >> 1;
 		// desaffecte la variable
 		voc.unassign(p);
 		voc.setReason(p, null);
 		voc.setLevel(p, -1);
 		// met a jour l'heuristique
 		order.undo(x);
 		// depile le litteral des affectations
 		trail.pop();
 		// met a jour les contraintes apres desaffectation du litteral :
 		// normalement, il n'y a rien a faire ici pour les prouveurs de type
 		// Chaff??
 		IVec<Undoable> undos = voc.undos(p);
 		assert undos != null;
 		while (undos.size() > 0) {
 			undos.last().undo(p);
 			undos.pop();
 		}
 	}
 
 	/**
 	 * Propagate activity to a constraint
 	 * 
 	 * @param confl
 	 *            a constraint
 	 */
 	public void claBumpActivity(Constr confl) {
 		confl.incActivity(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) {
 		order.updateVar(p);
 	}
 
 	private void claRescalActivity() {
 		for (int i = 0; i < learnts.size(); i++) {
 			learnts.get(i).rescaleBy(CLAUSE_RESCALE_FACTOR);
 		}
 		claInc *= CLAUSE_RESCALE_FACTOR;
 	}
 
 	/**
 	 * @return null if not conflict is found, else a conflicting constraint.
 	 */
 	public Constr propagate() {
 		while (qhead < trail.size()) {
 			stats.propagations++;
 			int p = trail.get(qhead++);
 			slistener.propagating(toDimacs(p), null);
 			order.assignLiteral(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> watched = dsfactory.getWatchesFor(p);
 
 			final int size = watched.size();
 			for (int i = 0; i < size; i++) {
 				stats.inspects++;
 				if (!watched.get(i).propagate(this, p)) {
 					// Constraint is conflicting: copy remaining watches to
 					// watches[p]
 					// and return constraint
 					dsfactory.conflictDetectedInWatchesFor(p, i);
 					qhead = trail.size(); // propQ.clear();
 					// FIXME enlever le transtypage
 					return (Constr) watched.get(i);
 				}
 			}
 		}
 		return null;
 	}
 
 	void record(Constr constr) {
 		constr.assertConstraint(this);
 		slistener.adding(toDimacs(constr.get(0)));
 		if (constr.size() == 1) {
 			stats.learnedliterals++;
 		} else {
 			learner.learns(constr);
 		}
 	}
 
 	/**
 	 * @return false ssi conflit imm?diat.
 	 */
 	public boolean assume(int p) {
 		// Precondition: assume propagation queue is empty
 		assert trail.size() == qhead;
 		trailLim.push(trail.size());
 		return enqueue(p);
 	}
 
 	/**
 	 * Revert to the state before the last push()
 	 */
 	private void cancel() {
 		// assert trail.size() == qhead || !undertimeout;
 		int decisionvar = trail.unsafeGet(trailLim.last());
 		slistener.backtracking(toDimacs(decisionvar));
 		for (int c = trail.size() - trailLim.last(); c > 0; c--) {
 			undoOne();
 		}
 		trailLim.pop();
 	}
 
 	/**
 	 * Restore literals
 	 */
 	private void cancelLearntLiterals(int learnedLiteralsLimit) {
 		learnedLiterals.clear();
 		// assert trail.size() == qhead || !undertimeout;
 		while (trail.size() > learnedLiteralsLimit) {
 			learnedLiterals.push(trail.last());
 			undoOne();
 		}
 		qhead = trail.size();
 		// learnedLiterals = 0;
 	}
 
 	/**
 	 * Cancel several levels of assumptions
 	 * 
 	 * @param level
 	 */
 	protected void cancelUntil(int level) {
 		while (decisionLevel() > level) {
 			cancel();
 		}
 		qhead = trail.size();
 	}
 
 	private final Pair analysisResult = new Pair();
 
 	private boolean[] fullmodel;
 
 	private IVecInt unsatExplanationInTermsOfAssumptions;
 
 	Lbool search(long nofConflicts, IVecInt assumps) {
 		assert rootLevel == decisionLevel();
 		stats.starts++;
 		int conflictC = 0;
 		int backjumpLevel;
 
 		// varDecay = 1 / params.varDecay;
 		order.setVarDecay(1 / params.getVarDecay());
 		claDecay = 1 / params.getClaDecay();
 
 		do {
 			slistener.beginLoop();
 			// propage les clauses unitaires
 			Constr confl = propagate();
 			assert trail.size() == qhead;
 
 			if (confl == null) {
 				// No conflict found
 				// simpliFYDB() prevents a correct use of
 				// constraints removal.
 				if (decisionLevel() == 0 && isDBSimplificationAllowed) {
 					// // Simplify the set of problem clause
 					// // iff rootLevel==0
 					stats.rootSimplifications++;
 					boolean ret = simplifyDB();
 					assert ret;
 				}
 				// was learnts.size() - nAssigns() > nofLearnts
 				// if (nofLearnts.obj >= 0 && learnts.size() > nofLearnts.obj) {
 				assert nAssigns() <= voc.realnVars();
 				if (nAssigns() == voc.realnVars()) {
 					slistener.solutionFound();
 					modelFound();
 					return Lbool.TRUE;
 				}
 				if (conflictC >= nofConflicts) {
 					// Reached bound on number of conflicts
 					// Force a restart
 					cancelUntil(rootLevel);
 					return Lbool.UNDEFINED;
 				}
 				if (needToReduceDB) {
 					reduceDB();
 					needToReduceDB = false;
 					// Runtime.getRuntime().gc();
 				}
 				// New variable decision
 				stats.decisions++;
 				int p = order.select();
 				assert p > 1;
 				slistener.assuming(toDimacs(p));
 				boolean ret = assume(p);
 				assert ret;
 			} else {
 				// un conflit apparait
 				stats.conflicts++;
 				conflictC++;
 				slistener.conflictFound(confl, decisionLevel(), trail.size());
 				conflictCount.newConflict();
 
 				if (decisionLevel() == rootLevel) {
 					// on est a la racine, la formule est inconsistante
 					unsatExplanationInTermsOfAssumptions = analyzeFinalConflictInTermsOfAssumptions(
 							confl, assumps, ILits.UNDEFINED);
 					return Lbool.FALSE;
 				}
 				// analyze conflict
 				analyze(confl, analysisResult);
 				assert analysisResult.backtrackLevel < decisionLevel();
 				backjumpLevel = Math.max(analysisResult.backtrackLevel,
 						rootLevel);
 				slistener.backjump(backjumpLevel);
 				cancelUntil(backjumpLevel);
 				if (backjumpLevel == rootLevel) {
 					conflictC = 0;
 				}
 				assert (decisionLevel() >= rootLevel)
 						&& (decisionLevel() >= analysisResult.backtrackLevel);
 				if (analysisResult.reason == null) {
 					return Lbool.FALSE;
 				}
 				record(analysisResult.reason);
 				analysisResult.reason = null;
 				decayActivities();
 			}
 		} while (undertimeout);
 		return Lbool.UNDEFINED; // timeout occured
 	}
 
 	protected void analyzeAtRootLevel(Constr conflict) {
 	}
 
 	/**
      * 
      */
 	void modelFound() {
 		model = new int[trail.size()];
 		fullmodel = new boolean[nVars()];
 		int index = 0;
 		for (int i = 1; i <= voc.nVars(); i++) {
 			if (voc.belongsToPool(i)) {
 				int p = voc.getFromPool(i);
 				if (!voc.isUnassigned(p)) {
 					model[index++] = voc.isSatisfied(p) ? i : -i;
 					fullmodel[i - 1] = voc.isSatisfied(p);
 				}
 			}
 		}
 		assert index == model.length;
 		cancelUntil(rootLevel);
 	}
 
 	public boolean model(int var) {
 		if (var <= 0 || var > nVars()) {
 			throw new IllegalArgumentException(
 					"Use a valid Dimacs var id as argument!"); //$NON-NLS-1$
 		}
 		if (fullmodel == null) {
 			throw new UnsupportedOperationException(
 					"Call the solve method first!!!"); //$NON-NLS-1$
 		}
 		return fullmodel[var - 1];
 	}
 
 	public void clearLearntClauses() {
 		for (Iterator<Constr> iterator = learnts.iterator(); iterator.hasNext();)
 			iterator.next().remove(this);
 		learnts.clear();
 		learnedLiterals.clear();
 	}
 
 	protected void reduceDB() {
 		sortOnActivity();
 		stats.reduceddb++;
 		learnedConstraintsDeletionStrategy.reduce(learnts);
 		System.gc();
 	}
 
 	/**
 	 * @param learnts
 	 */
 	private void sortOnActivity() {
 		learnts.sort(comparator);
 	}
 
 	/**
      * 
      */
 	protected void decayActivities() {
 		order.varDecayActivity();
 		claDecayActivity();
 	}
 
 	/**
      * 
      */
 	private void claDecayActivity() {
 		claInc *= 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 ConflictTimer conflictCount;
 
 	private transient Timer timer;
 
 	public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
 		return isSatisfiable(assumps, false);
 	}
 
 	interface LearnedConstraintsDeletionStrategy extends Serializable {
 
 		void init();
 
 		ConflictTimer getTimer();
 
 		void reduce(IVec<Constr> learnedConstrs);
 
 		void onConflict(Constr outLearnt);
 
 		void onConflictAnalysis(Constr reason);
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public final LearnedConstraintsDeletionStrategy memory_based = new LearnedConstraintsDeletionStrategy() {
 
 		/**
 		 * 
 		 */
 		private static final long serialVersionUID = 1L;
 
 		final long memorybound = Runtime.getRuntime().freeMemory() / 10;
 
 		private final ConflictTimer freeMem = new ConflictTimerAdapter(500) {
 			private static final long serialVersionUID = 1L;
 
 			@Override
 			void run() {
 				long freemem = Runtime.getRuntime().freeMemory();
 				// System.out.println("c Free memory "+freemem);
 				if (freemem < memorybound) {
 					// Reduce the set of learnt clauses
 					needToReduceDB = true;
 				}
 			}
 		};
 
 		public void reduce(IVec<Constr> learnedConstrs) {
 			int i, j;
 			for (i = j = 0; i < learnts.size() / 2; i++) {
 				Constr c = learnts.get(i);
 				if (c.locked() || c.size() == 2) {
 					learnts.set(j++, learnts.get(i));
 				} else {
 					c.remove(Solver.this);
 				}
 			}
 			for (; i < learnts.size(); i++) {
 				learnts.set(j++, learnts.get(i));
 			}
 			if (verbose) {
 				System.out.println(getLogPrefix()
 						+ "cleaning " + (learnts.size() - j) //$NON-NLS-1$
 						+ " clauses out of " + learnts.size()); //$NON-NLS-1$ //$NON-NLS-2$
 			}
 			learnts.shrinkTo(j);
 		}
 
 		public ConflictTimer getTimer() {
 			return freeMem;
 		}
 
 		@Override
 		public String toString() {
 			return "Memory based learned constraints deletion strategy";
 		}
 
 		public void init() {
 			// do nothing
 		}
 
 		public void onConflict(Constr constr) {
 			// do nothing
 
 		}
 
 		public void onConflictAnalysis(Constr reason) {
 			if (reason.learnt())
 				claBumpActivity(reason);
 		}
 	};
 
 	/**
 	 * @since 2.1
 	 */
 	public final LearnedConstraintsDeletionStrategy glucose = new 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 = 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
 			void run() {
 				nbconflict += bound();
 				if (nbconflict >= nextbound) {
 					nextbound += INC_CLAUSE;
 					if (nextbound > wall) {
 						nextbound = wall;
 					}
 					nbconflict = 0;
 					needToReduceDB = true;
 				}
 			}
 		};
 
 		public void reduce(IVec<Constr> learnedConstrs) {
 			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++, learnts.get(i));
 				} else {
 					c.remove(Solver.this);
 				}
 			}
 			if (verbose) {
 				System.out
 						.println(getLogPrefix()
 								+ "cleaning " + (learnedConstrs.size() - j) //$NON-NLS-1$
 								+ " clauses out of " + learnedConstrs.size() + " with flag " + flag + "/" + stats.conflicts); //$NON-NLS-1$ //$NON-NLS-2$
 			}
 			learnts.shrinkTo(j);
 
 		}
 
 		public ConflictTimer getTimer() {
 			return clauseManagement;
 		}
 
 		@Override
 		public String toString() {
 			return "Glucose learned constraints deletion strategy";
 		}
 
 		public void init() {
 			final int howmany = voc.nVars();
 			wall = constrs.size() > 10000 ? constrs.size() : 10000;
 			if (flags.length <= howmany) {
 				flags = new int[howmany + 1];
 			}
 
 		}
 
 		public void onConflict(Constr constr) {
 			int nblevel = 1;
 			flag++;
 			int currentLevel;
 			for (int i = 1; i < constr.size(); i++) {
 				currentLevel = voc.getLevel(constr.get(i));
 				if (flags[currentLevel] != flag) {
 					flags[currentLevel] = flag;
 					nblevel++;
 				}
 			}
 			constr.incActivity(nblevel);
 		}
 
 		public void onConflictAnalysis(Constr reason) {
 			// do nothing
 		}
 	};
 
 	private LearnedConstraintsDeletionStrategy learnedConstraintsDeletionStrategy = glucose;
 
 	/**
 	 * @param lcds
 	 * @since 2.1
 	 */
 	public void setLearnedConstraintsDeletionStrategy(
 			LearnedConstraintsDeletionStrategy lcds) {
 		learnedConstraintsDeletionStrategy = lcds;
 	}
 
 	public boolean isSatisfiable(IVecInt assumps, boolean global)
 			throws TimeoutException {
 		Lbool status = Lbool.UNDEFINED;
 		undertimeout = true;
 		final int howmany = voc.nVars();
 		if (mseen.length <= howmany) {
 			mseen = new boolean[howmany + 1];
 		}
 		trail.ensure(howmany);
 		trailLim.ensure(howmany);
 		learnedLiterals.ensure(howmany);
 		timebegin = System.currentTimeMillis();
 		slistener.start();
 		model = null; // forget about previous model
 		fullmodel = null;
 		unsatExplanationInTermsOfAssumptions = null;
 		order.init();
 		learnedConstraintsDeletionStrategy.init();
 
 		int learnedLiteralsLimit = trail.size();
 
 		// push previously learned literals
 		for (IteratorInt iterator = learnedLiterals.iterator(); iterator
 				.hasNext();) {
 			enqueue(iterator.next());
 		}
 
 		// propagate constraints
 		Constr confl = propagate();
 		if (confl != null) {
 			analyzeAtRootLevel(confl);
 			slistener.conflictFound(confl, 0, 0);
 			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 = voc.getFromPool(assump);
 			if (!assume(p) || ((confl = propagate()) != null)) {
 				if (confl == null) {
 					slistener.conflictFound(p);
 					unsatExplanationInTermsOfAssumptions = analyzeFinalConflictInTermsOfAssumptions(
 							null, assumps, p);
 					unsatExplanationInTermsOfAssumptions.push(assump);
 				} else {
 					slistener.conflictFound(confl, decisionLevel(),
 							trail.size());
 					unsatExplanationInTermsOfAssumptions = analyzeFinalConflictInTermsOfAssumptions(
 							confl, assumps, ILits.UNDEFINED);
 				}
 
 				slistener.end(Lbool.FALSE);
 				cancelUntil(0);
 				cancelLearntLiterals(learnedLiteralsLimit);
 				return false;
 			}
 		}
 		rootLevel = decisionLevel();
 		// moved initialization here if new literals are added in the
 		// assumptions.
 		order.init(); // duplicated on purpose
 		learner.init();
 
 		boolean firstTimeGlobal = false;
 		if (timeBasedTimeout) {
 			if (!global || timer == null) {
 				firstTimeGlobal = true;
 				TimerTask stopMe = new TimerTask() {
 					@Override
 					public void run() {
 						undertimeout = false;
 					}
 				};
 				timer = new Timer(true);
 				timer.schedule(stopMe, timeout);
 				conflictCount = learnedConstraintsDeletionStrategy.getTimer();
 			}
 		} else {
 			if (!global || conflictCount == null) {
 				firstTimeGlobal = true;
 				ConflictTimer conflictTimeout = new ConflictTimerAdapter(
 						(int) timeout) {
 					private static final long serialVersionUID = 1L;
 
 					@Override
 					public void run() {
 						undertimeout = false;
 					}
 				};
 				conflictCount = new ConflictTimerContainer().add(
 						conflictTimeout).add(
 						learnedConstraintsDeletionStrategy.getTimer());
 			}
 		}
 		if (!global || firstTimeGlobal)
 			restarter.init(params);
 		needToReduceDB = false;
 		// Solve
 		while ((status == Lbool.UNDEFINED) && undertimeout) {
 			status = search(restarter.nextRestartNumberOfConflict(), assumps);
 			if (status == Lbool.UNDEFINED) {
 				restarter.onRestart();
 				slistener.restarting();
 			}
 		}
 
 		cancelUntil(0);
 		cancelLearntLiterals(learnedLiteralsLimit);
 		if (!global && timeBasedTimeout) {
 			timer.cancel();
 			timer = null;
 		}
 		slistener.end(status);
 		if (!undertimeout) {
 			String message = " Timeout (" + timeout
 					+ (timeBasedTimeout ? "s" : " conflicts") + ") exceeded";
 			throw new TimeoutException(message); //$NON-NLS-1$//$NON-NLS-2$
 		}
 		return status == Lbool.TRUE;
 	}
 
 	public void printInfos(PrintWriter out, String prefix) {
 		out.print(prefix);
 		out.println("constraints type ");
 		for (Map.Entry<String, Counter> entry : constrTypes.entrySet()) {
 			out.println(prefix + entry.getKey() + " => " + entry.getValue());
 		}
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public void printLearntClausesInfos(PrintWriter out, String prefix) {
 		Map<String, Counter> learntTypes = new HashMap<String, Counter>();
 		for (Iterator<Constr> it = 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 stats;
 	}
 
 	/**
 	 * 
 	 * @param myStats
 	 * @since 2.2
 	 */
 	protected void initStats(SolverStats myStats) {
 		this.stats = myStats;
 	}
 
 	public IOrder getOrder() {
 		return order;
 	}
 
 	public void setOrder(IOrder h) {
 		order = h;
 		order.setLits(voc);
 	}
 
 	public ILits getVocabulary() {
 		return voc;
 	}
 
 	public void reset() {
 		trail.clear();
 		trailLim.clear();
 		qhead = 0;
 		for (Iterator<Constr> iterator = constrs.iterator(); iterator.hasNext();)
 			iterator.next().remove(this);
 		constrs.clear();
 		clearLearntClauses();
 		voc.resetPool();
 		dsfactory.reset();
 		stats.reset();
 		constrTypes.clear();
 	}
 
 	public int nVars() {
 		return voc.nVars();
 	}
 
 	/**
 	 * @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) {
 			constrs.push(constr);
 			String type = constr.getClass().getName();
 			Counter count = constrTypes.get(type);
 			if (count == null) {
 				constrTypes.put(type, new Counter());
 			} else {
 				count.inc();
 			}
 		}
 		return constr;
 	}
 
 	public DataStructureFactory getDSFactory() {
 		return dsfactory;
 	}
 
 	public IVecInt getOutLearnt() {
 		return 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 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, String prefix) {
 		stats.printStat(out, prefix);
 		double cputime = (System.currentTimeMillis() - timebegin) / 1000;
 		out.println(prefix
 				+ "speed (assignments/second)\t: " + stats.propagations //$NON-NLS-1$
 				/ cputime);
 		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 = { analyzer, dsfactory, learner, params, order,
 				simplifier, restarter, 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 (timeBasedTimeout) {
 			stb.append(timeout / 1000);
 			stb.append("s\n");
 		} else {
 			stb.append(timeout);
 			stb.append(" conflicts\n");
 		}
 		stb.append(prefix);
 		stb.append("DB Simplification allowed=");
 		stb.append(isDBSimplificationAllowed);
 		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) (timeBasedTimeout ? timeout / 1000 : timeout);
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public long getTimeoutMs() {
 		if (!timeBasedTimeout) {
 			throw new UnsupportedOperationException(
 					"The timeout is given in number of conflicts!");
 		}
 		return timeout;
 	}
 
 	public void setExpectedNumberOfClauses(int nb) {
 		constrs.ensure(nb);
 	}
 
 	public Map<String, Number> getStat() {
 		return 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 isDBSimplificationAllowed;
 	}
 
 	public void setDBSimplificationAllowed(boolean status) {
 		isDBSimplificationAllowed = status;
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public int nextFreeVarId(boolean reserve) {
 		return voc.nextFreeVarId(reserve);
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public IConstr addBlockingClause(IVecInt literals)
 			throws ContradictionException {
 		return addClause(literals);
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public void unset(int p) {
 		int current = trail.last();
 		while (current != p) {
 			undoOne();
 			current = trail.last();
 		}
 		undoOne();
 	}
 
 	/**
 	 * @since 2.2
 	 */
 	public void setLogPrefix(String prefix) {
 		this.prefix = prefix;
 	}
 
 	/**
 	 * @since 2.2
 	 */
 	public String getLogPrefix() {
 		return prefix;
 	}
 
 	/**
 	 * @since 2.2
 	 */
 	public IVecInt unsatExplanation() {
 		return unsatExplanationInTermsOfAssumptions;
 	}
 
 }
 
 class ActivityComparator implements Comparator<Constr>, Serializable {
 
 	private static final long serialVersionUID = 1L;
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
 	 */
 	public int compare(Constr c1, Constr c2) {
 		long delta = Math.round(c1.getActivity() - c2.getActivity());
 		if (delta == 0) {
 			return c1.size() - c2.size();
 		}
 		return (int) delta;
 	}
 }
 
 interface ConflictTimer {
 
 	void reset();
 
 	void newConflict();
 }
 
 abstract class ConflictTimerAdapter implements Serializable, ConflictTimer {
 
 	/**
 	 * 
 	 */
 	private static final long serialVersionUID = 1L;
 
 	private int counter;
 
 	private final int bound;
 
 	ConflictTimerAdapter(final int bound) {
 		this.bound = bound;
 		counter = 0;
 	}
 
 	public void reset() {
 		counter = 0;
 	}
 
 	public void newConflict() {
 		counter++;
 		if (counter == bound) {
 			run();
 			counter = 0;
 		}
 	}
 
 	abstract void run();
 
 	public int bound() {
 		return bound;
 	}
 }
 
 class ConflictTimerContainer implements Serializable, ConflictTimer {
 
 	/**
 	 * 
 	 */
 	private static final long serialVersionUID = 1L;
 
 	private final IVec<ConflictTimer> timers = new Vec<ConflictTimer>();
 
 	ConflictTimerContainer add(ConflictTimer timer) {
 		timers.push(timer);
 		return this;
 	}
 
 	public void reset() {
 		Iterator<ConflictTimer> it = timers.iterator();
 		while (it.hasNext()) {
 			it.next().reset();
 		}
 	}
 
 	public void newConflict() {
 		Iterator<ConflictTimer> it = timers.iterator();
 		while (it.hasNext()) {
 			it.next().newConflict();
 		}
 	}
 }