/*******************************************************************************
    * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
    *
    * All rights reserved. This program and the accompanying materials
    * are made available under the terms of the Eclipse Public License v1.0
    * which accompanies this distribution, and is available at
    * http://www.eclipse.org/legal/epl-v10.html
    *
    * Alternatively, the contents of this file may be used under the terms of
   * either the GNU Lesser General Public License Version 2.1 or later (the
   * "LGPL"), in which case the provisions of the LGPL are applicable instead
   * of those above. If you wish to allow use of your version of this file only
   * under the terms of the LGPL, and not to allow others to use your version of
   * this file under the terms of the EPL, indicate your decision by deleting
   * the provisions above and replace them with the notice and other provisions
   * required by the LGPL. If you do not delete the provisions above, a recipient
   * may use your version of this file under the terms of the EPL or the LGPL.
   * 
   * Based on the original MiniSat specification from:
   * 
   * An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
   * Sixth International Conference on Theory and Applications of Satisfiability
   * Testing, LNCS 2919, pp 502-518, 2003.
   *
   * See www.minisat.se for the original solver in C++.
   * 
   *******************************************************************************/
  package org.sat4j.tools;
  
  import java.io.PrintStream;
  import java.io.PrintWriter;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  
  import org.sat4j.core.ASolverFactory;
  import org.sat4j.core.ConstrGroup;
  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.SearchListener;
  import org.sat4j.specs.TimeoutException;
  
  public class ManyCore<S extends ISolver> implements ISolver, OutcomeListener {
  
  	private static final long MINIMAL_MEMORY_REQUIREMENT = 500000000L;
  
  	private static final int NORMAL_SLEEP = 500;
  
  	private static final int FAST_SLEEP = 50;
  
  	/**
  	 * 
  	 */
  	private static final long serialVersionUID = 1L;
  
  	private final String[] availableSolvers; // = { };
  
  	protected final List<S> solvers;
  	protected final int numberOfSolvers;
  	private int winnerId;
  	private boolean resultFound;
  	private volatile int remainingSolvers;
  	private volatile int sleepTime;
  	private volatile boolean solved;
  
  	public ManyCore(ASolverFactory<S> factory, String... solverNames) {
  		availableSolvers = solverNames;
  		numberOfSolvers = computeNumberOfSolversInParallel(solverNames.length);
  		solvers = new ArrayList<S>(numberOfSolvers);
  		for (int i = 0; i < numberOfSolvers; i++) {
  			solvers.add(factory.createSolverByName(availableSolvers[i]));
  		}
  	}
  
  	private int computeNumberOfSolversInParallel(int upperBound) {
  		Runtime runtime = Runtime.getRuntime();
  		long memory = runtime.maxMemory();
  		int numberOfCores = runtime.availableProcessors();
  		if (memory > MINIMAL_MEMORY_REQUIREMENT) {
  			return upperBound < numberOfCores ? upperBound : numberOfCores;
  		} else {
  			return 1;
  		}
  	}
  
  	/**
  	 * Create a parallel solver from a list of solvers and a list of names.
  	 * 
  	 * @param names
  	 *            a String to describe each solver in the messages.
  	 * @param solverObjects
  	 *            the solvers
  	 */
  	public ManyCore(String[] names, S... solverObjects) {
  		this(solverObjects);
 		for (int i = 0; i < names.length; i++) {
 			availableSolvers[i] = names[i];
 		}
 	}
 
 	public ManyCore(S... solverObjects) {
 		availableSolvers = new String[solverObjects.length];
 		for (int i = 0; i < solverObjects.length; i++) {
 			availableSolvers[i] = "solver" + i;
 		}
 		numberOfSolvers = computeNumberOfSolversInParallel(solverObjects.length);
 		solvers = new ArrayList<S>(numberOfSolvers);
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.add(solverObjects[i]);
 		}
 	}
 
 	public void addAllClauses(IVec<IVecInt> clauses)
 			throws ContradictionException {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).addAllClauses(clauses);
 		}
 	}
 
 	public IConstr addAtLeast(IVecInt literals, int degree)
 			throws ContradictionException {
 		ConstrGroup group = new ConstrGroup(false);
 		for (int i = 0; i < numberOfSolvers; i++) {
 			group.add(solvers.get(i).addAtLeast(literals, degree));
 		}
 		return group;
 	}
 
 	public IConstr addAtMost(IVecInt literals, int degree)
 			throws ContradictionException {
 		ConstrGroup group = new ConstrGroup(false);
 		for (int i = 0; i < numberOfSolvers; i++) {
 			group.add(solvers.get(i).addAtMost(literals, degree));
 		}
 		return group;
 	}
 
 	public IConstr addExactly(IVecInt literals, int n)
 			throws ContradictionException {
 		ConstrGroup group = new ConstrGroup(false);
 		for (int i = 0; i < numberOfSolvers; i++) {
 			group.add(solvers.get(i).addExactly(literals, n));
 		}
 		return group;
 	}
 
 	public IConstr addClause(IVecInt literals) throws ContradictionException {
 		ConstrGroup group = new ConstrGroup(false);
 		for (int i = 0; i < numberOfSolvers; i++) {
 			group.add(solvers.get(i).addClause(literals));
 		}
 		return group;
 	}
 
 	public void clearLearntClauses() {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).clearLearntClauses();
 		}
 	}
 
 	public void expireTimeout() {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).expireTimeout();
 		}
 		sleepTime = FAST_SLEEP;
 	}
 
 	public Map<String, Number> getStat() {
 		return solvers.get(winnerId).getStat();
 	}
 
 	public int getTimeout() {
 		return solvers.get(0).getTimeout();
 	}
 
 	public long getTimeoutMs() {
 		return solvers.get(0).getTimeoutMs();
 	}
 
 	public int newVar() {
 		throw new UnsupportedOperationException();
 	}
 
 	public int newVar(int howmany) {
 		int result = 0;
 		for (int i = 0; i < numberOfSolvers; i++) {
 			result = solvers.get(i).newVar(howmany);
 		}
 		return result;
 	}
 
 	@Deprecated
 	public void printStat(PrintStream out, String prefix) {
 		solvers.get(winnerId).printStat(out, prefix);
 	}
 
 	public void printStat(PrintWriter out, String prefix) {
 		solvers.get(winnerId).printStat(out, prefix);
 	}
 
 	public boolean removeConstr(IConstr c) {
 		if (c instanceof ConstrGroup) {
 			ConstrGroup group = (ConstrGroup) c;
 			boolean removed = true;
 			IConstr toRemove;
 			for (int i = 0; i < numberOfSolvers; i++) {
 				toRemove = group.getConstr(i);
 				if (toRemove != null) {
 					removed = removed & solvers.get(i).removeConstr(toRemove);
 				}
 			}
 			return removed;
 		}
 		throw new IllegalArgumentException(
 				"Can only remove a group of constraints!");
 	}
 
 	public void reset() {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).reset();
 		}
 	}
 
 	public void setExpectedNumberOfClauses(int nb) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).setExpectedNumberOfClauses(nb);
 		}
 	}
 
 	public void setTimeout(int t) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).setTimeout(t);
 		}
 	}
 
 	public void setTimeoutMs(long t) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).setTimeoutMs(t);
 		}
 	}
 
 	public void setTimeoutOnConflicts(int count) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).setTimeoutOnConflicts(count);
 		}
 	}
 
 	public String toString(String prefix) {
 		StringBuffer res = new StringBuffer();
 		res.append(prefix);
 		res.append("ManyCore solver with ");
 		res.append(numberOfSolvers);
 		res.append(" solvers running in parallel");
 		res.append("\n");
 		for (int i = 0; i < numberOfSolvers; i++) {
 			res.append(solvers.get(i).toString(prefix));
 			if (i < numberOfSolvers - 1) {
 				res.append("\n");
 			}
 		}
 		return res.toString();
 	}
 
 	public int[] findModel() throws TimeoutException {
 		if (isSatisfiable()) {
 			return model();
 		}
 		// 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();
 		}
 		// A zero length array would mean that the formula is a tautology.
 		return null;
 	}
 
 	public boolean isSatisfiable() throws TimeoutException {
 		return isSatisfiable(VecInt.EMPTY, false);
 	}
 
 	public boolean isSatisfiable(IVecInt assumps, boolean globalTimeout)
 			throws TimeoutException {
 		remainingSolvers = numberOfSolvers;
 		solved = false;
 		for (int i = 0; i < numberOfSolvers; i++) {
 			new Thread(new RunnableSolver(i, solvers.get(i), assumps,
 					globalTimeout, this)).start();
 		}
 		try {
 			sleepTime = NORMAL_SLEEP;
 			do {
 				Thread.sleep(sleepTime);
 			} while (remainingSolvers > 0);
 		} catch (InterruptedException e) {
 			// TODO: handle exception
 		}
 		if (!solved) {
 			assert remainingSolvers == 0;
 			throw new TimeoutException();
 		}
 		return resultFound;
 	}
 
 	public boolean isSatisfiable(boolean globalTimeout) throws TimeoutException {
 		throw new UnsupportedOperationException();
 	}
 
 	public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
 		throw new UnsupportedOperationException();
 	}
 
 	public int[] model() {
 		return solvers.get(winnerId).model();
 	}
 
 	public boolean model(int var) {
 		return solvers.get(winnerId).model(var);
 	}
 
 	public int nConstraints() {
 		return solvers.get(0).nConstraints();
 	}
 
 	public int nVars() {
 		return solvers.get(0).nVars();
 	}
 
 	public void printInfos(PrintWriter out, String prefix) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).printInfos(out, prefix);
 		}
 	}
 
 	public synchronized void onFinishWithAnswer(boolean finished,
 			boolean result, int index) {
 		if (finished && !solved) {
 			winnerId = index;
 			solved = true;
 			resultFound = result;
 			for (int i = 0; i < numberOfSolvers; i++) {
 				if (i != winnerId)
 					solvers.get(i).expireTimeout();
 			}
 			sleepTime = FAST_SLEEP;
 			System.out.println(getLogPrefix() + " And the winner is "
 					+ availableSolvers[winnerId]);
 		}
 		remainingSolvers--;
 	}
 
 	public boolean isDBSimplificationAllowed() {
 		return solvers.get(0).isDBSimplificationAllowed();
 	}
 
 	public void setDBSimplificationAllowed(boolean status) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(0).setDBSimplificationAllowed(status);
 		}
 	}
 
 	public void setSearchListener(SearchListener sl) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).setSearchListener(sl);
 		}
 	}
 
 	/**
 	 * @since 2.2
 	 */
 	public SearchListener getSearchListener() {
 		return solvers.get(0).getSearchListener();
 	}
 
 	public int nextFreeVarId(boolean reserve) {
 		return solvers.get(0).nextFreeVarId(reserve);
 	}
 
 	public IConstr addBlockingClause(IVecInt literals)
 			throws ContradictionException {
 		ConstrGroup group = new ConstrGroup(false);
 		for (int i = 0; i < numberOfSolvers; i++) {
 			group.add(solvers.get(i).addBlockingClause(literals));
 		}
 		return group;
 	}
 
 	public boolean removeSubsumedConstr(IConstr c) {
 		if (c instanceof ConstrGroup) {
 			ConstrGroup group = (ConstrGroup) c;
 			boolean removed = true;
 			IConstr toRemove;
 			for (int i = 0; i < numberOfSolvers; i++) {
 				toRemove = group.getConstr(i);
 				if (toRemove != null) {
 					removed = removed
 							& solvers.get(i).removeSubsumedConstr(toRemove);
 				}
 			}
 			return removed;
 		}
 		throw new IllegalArgumentException(
 				"Can only remove a group of constraints!");
 	}
 
 	public boolean isVerbose() {
 		return solvers.get(0).isVerbose();
 	}
 
 	public void setVerbose(boolean value) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).setVerbose(value);
 		}
 	}
 
 	public void setLogPrefix(String prefix) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).setLogPrefix(prefix);
 		}
 
 	}
 
 	public String getLogPrefix() {
 		return solvers.get(0).getLogPrefix();
 	}
 
 	public IVecInt unsatExplanation() {
 		return solvers.get(winnerId).unsatExplanation();
 	}
 
 	public int[] primeImplicant() {
 		return solvers.get(winnerId).primeImplicant();
 	}
 
 	public List<S> getSolvers() {
 		return new ArrayList<S>(this.solvers);
 	}
 
 	public int[] modelWithInternalVariables() {
 		return solvers.get(winnerId).modelWithInternalVariables();
 	}
 
 	public int realNumberOfVariables() {
 		return solvers.get(0).realNumberOfVariables();
 	}
 
 	public void registerLiteral(int p) {
 		for (int i = 0; i < numberOfSolvers; i++) {
 			solvers.get(i).registerLiteral(p);
 		}
 
 	}
 }
 
 interface OutcomeListener {
 	void onFinishWithAnswer(boolean finished, boolean result, int index);
 }
 
 class RunnableSolver implements Runnable {
 
 	private final int index;
 	private final ISolver solver;
 	private final OutcomeListener ol;
 	private final IVecInt assumps;
 	private final boolean globalTimeout;
 
 	public RunnableSolver(int i, ISolver solver, IVecInt assumps,
 			boolean globalTimeout, OutcomeListener ol) {
 		index = i;
 		this.solver = solver;
 		this.ol = ol;
 		this.assumps = assumps;
 		this.globalTimeout = globalTimeout;
 	}
 
 	public void run() {
 		try {
 			boolean result = solver.isSatisfiable(assumps, globalTimeout);
 			ol.onFinishWithAnswer(true, result, index);
 		} catch (Exception e) {
 			ol.onFinishWithAnswer(false, false, index);
 		}
 	}
 
 }