/*******************************************************************************
    * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le
    *
    * 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
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  package org.sat4j.maxsat;
  
  import java.math.BigInteger;
  
  import org.sat4j.core.Vec;
  import org.sat4j.core.VecInt;
  import org.sat4j.minisat.core.DataStructureFactory;
  import org.sat4j.minisat.core.IOrder;
  import org.sat4j.minisat.core.Solver;
  import org.sat4j.pb.IPBSolver;
  import org.sat4j.pb.ObjectiveFunction;
  import org.sat4j.pb.PBSolverDecorator;
  import org.sat4j.pb.orders.VarOrderHeapObjective;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.IOptimizationProblem;
  import org.sat4j.specs.IVec;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.IteratorInt;
  import org.sat4j.specs.TimeoutException;
  
  /**
   * A decorator for solving weighted MAX SAT problems.
   * 
   * The first value of the list of literals in the addClause() method contains
   * the weight of the clause.
   * 
   * @author daniel
   * 
   */
  public class WeightedMaxSatDecorator extends PBSolverDecorator implements
  		IOptimizationProblem {
  
  	/**
       * 
       */
  	private static final long serialVersionUID = 1L;
  
  	protected int nborigvars;
  
  	private int nbexpectedclauses;
  
  	private long falsifiedWeight;
  
  	protected int nbnewvar;
  
  	protected int[] prevmodel;
  	protected boolean[] prevboolmodel;
  
  	protected int[] prevfullmodel;
  
  	public WeightedMaxSatDecorator(IPBSolver solver) {
  		super(solver);
  		IOrder<?> order = ((Solver<?, ? extends DataStructureFactory<?>>) solver)
  				.getOrder();
  		if (order instanceof VarOrderHeapObjective) {
  			((VarOrderHeapObjective) order).setObjectiveFunction(obj);
  		}
  	}
  
  	@Override
  	public int newVar(int howmany) {
  		nborigvars = super.newVar(howmany);
  		return nborigvars;
  	}
  
  	@Override
  	public void setExpectedNumberOfClauses(int nb) {
  		nbexpectedclauses = nb;
  		lits.ensure(nb);
  		falsifiedWeight = 0;
  		super.setExpectedNumberOfClauses(nb);
  		super.newVar(nborigvars + nbexpectedclauses);
  	}
  
  	@Override
  	public int[] model() {
  		return prevmodel;
  	}
  
  	@Override
 	public boolean model(int var) {
 		return prevboolmodel[var - 1];
 	}
 
 	protected int top = Integer.MAX_VALUE;
 
 	public void setTopWeight(int top) {
 		this.top = top;
 	}
 
 	/**
 	 * Add a set of literals to the solver.
 	 * 
 	 * Here the assumption is that the first literal (literals[0]) is the weight
 	 * of the constraint as found in the MAXSAT evaluation. if the weight is
 	 * greater or equal to the top weight, then the clause is hard, else it is
 	 * soft.
 	 * 
 	 * @param literals
 	 *            a weighted clause, the weight being the first element of the
 	 *            vector.
 	 * @see #setTopWeight(int)
 	 */
 	@Override
 	public IConstr addClause(IVecInt literals) throws ContradictionException {
 		int weight = literals.get(0);
 		literals.delete(0);
 		return addSoftClause(weight, literals);
 	}
 
 	/**
 	 * Add a hard clause in the solver, i.e. a clause that must be satisfied.
 	 * 
 	 * @param literals
 	 *            the clause
 	 * @return the constraint is it is not trivially satisfied.
 	 * @throws ContradictionException
 	 */
 	public IConstr addHardClause(IVecInt literals)
 			throws ContradictionException {
 		return super.addClause(literals);
 	}
 
 	/**
 	 * Add a soft clause in the solver, i.e. a clause with a weight of 1.
 	 * 
 	 * @param literals
 	 *            the clause.
 	 * @return the constraint is it is not trivially satisfied.
 	 * @throws ContradictionException
 	 */
 	public IConstr addSoftClause(IVecInt literals)
 			throws ContradictionException {
 		return addSoftClause(1, literals);
 	}
 
 	/**
 	 * Add a soft clause to the solver.
 	 * 
 	 * if the weight of the clause is greater of equal to the top weight, the
 	 * clause will be considered as a hard clause.
 	 * 
 	 * @param weight
 	 *            the weight of the clause
 	 * @param literals
 	 *            the clause
 	 * @return the constraint is it is not trivially satisfied.
 	 * @throws ContradictionException
 	 */
 	public IConstr addSoftClause(int weight, IVecInt literals)
 			throws ContradictionException {
 		if (weight < top) {
 			BigInteger bigweight = BigInteger.valueOf(weight);
 			if (literals.size() == 2) {
 				// if there is only a coefficient and a literal, no need to
 				// create
 				// a new variable
 				// check first if the literal is already in the list:
 				int lit = -literals.get(1);
 				int index = lits.containsAt(lit);
 				if (index != -1) {
 					coefs.set(index, coefs.get(index).add(bigweight));
 				} else {
 					// check if the opposite literal is already there
 					index = lits.containsAt(-lit);
 					if (index != -1) {
 						falsifiedWeight += weight;
 						BigInteger oldw = coefs.get(index);
 						BigInteger diff = oldw.subtract(bigweight);
 						if (diff.signum() > 0) {
 							coefs.set(index, diff);
 						} else if (diff.signum() < 0) {
 							lits.set(index, lit);
 							coefs.set(index, diff.abs());
 							// remove from falsifiedWeight the
 							// part of the weight that will remain
 							// in the objective function
 							falsifiedWeight += diff.intValue();
 						} else {
 							assert diff.signum() == 0;
 							lits.delete(index);
 							coefs.delete(index);
 						}
 					} else {
 						lits.push(lit);
 						coefs.push(bigweight);
 					}
 				}
 				return null;
 			}
 			coefs.push(bigweight);
 			int newvar = nborigvars + ++nbnewvar;
 			literals.push(newvar);
 			lits.push(newvar);
 		}
 		return super.addClause(literals);
 	}
 
 	/**
 	 * Set some literals whose sum must be minimized.
 	 * 
 	 * @param literals
 	 *            the sum of those literals must be minimized.
 	 */
 	public void addLiteralsToMinimize(IVecInt literals) {
 		for (IteratorInt it = literals.iterator(); it.hasNext();) {
 			lits.push(it.next());
 			coefs.push(BigInteger.ONE);
 		}
 	}
 
 	/**
 	 * Set some literals whose sum must be minimized.
 	 * 
 	 * @param literals
 	 *            the sum of those literals must be minimized.
 	 * @param coefficients
 	 *            the weight of the literals.
 	 */
 	public void addWeightedLiteralsToMinimize(IVecInt literals,
 			IVec<BigInteger> coefficients) {
 		if (literals.size() != coefs.size())
 			throw new IllegalArgumentException();
 		for (int i = 0; i < literals.size(); i++) {
 			lits.push(literals.get(i));
 			coefs.push(coefficients.get(i));
 		}
 	}
 
 	/**
 	 * Set some literals whose sum must be minimized.
 	 * 
 	 * @param literals
 	 *            the sum of those literals must be minimized.
 	 * @param coefficients
 	 *            the weight of the literals.
 	 */
 	public void addWeightedLiteralsToMinimize(IVecInt literals,
 			IVecInt coefficients) {
 		if (literals.size() != coefficients.size())
 			throw new IllegalArgumentException();
 		for (int i = 0; i < literals.size(); i++) {
 			lits.push(literals.get(i));
 			coefs.push(BigInteger.valueOf(coefficients.get(i)));
 		}
 	}
 
 	public boolean admitABetterSolution() throws TimeoutException {
 		boolean result = super.isSatisfiable(true);
 		if (result) {
 			prevboolmodel = new boolean[nVars()];
 			for (int i = 0; i < nVars(); i++) {
 				prevboolmodel[i] = decorated().model(i + 1);
 			}
 			int nbtotalvars = nborigvars + nbnewvar;
 			if (prevfullmodel == null)
 				prevfullmodel = new int[nbtotalvars];
 			for (int i = 1; i <= nbtotalvars; i++) {
 				prevfullmodel[i - 1] = super.model(i) ? i : -i;
 			}
 			prevmodel = new int[nborigvars];
 			for (int i = 0; i < nborigvars; i++) {
 				prevmodel[i] = prevfullmodel[i];
 			}
 		}
 		return result;
 	}
 
 	@Override
 	public void reset() {
 		coefs.clear();
 		lits.clear();
 		nbnewvar = 0;
 		super.reset();
 	}
 
 	public boolean hasNoObjectiveFunction() {
 		return false;
 	}
 
 	public boolean nonOptimalMeansSatisfiable() {
 		return false;
 	}
 
 	private int counter;
 
 	public Number calculateObjective() {
 		counter = 0;
 		for (int q : prevfullmodel) {
 			int index = lits.containsAt(q);
 			if (index != -1) {
 				counter += coefs.get(index).intValue();
 			}
 		}
 		return falsifiedWeight + counter;
 	}
 
 	private final IVecInt lits = new VecInt();
 
 	private final IVec<BigInteger> coefs = new Vec<BigInteger>();
 
 	private final ObjectiveFunction obj = new ObjectiveFunction(lits, coefs);
 
 	public void discard() throws ContradictionException {
 		assert lits.size() == coefs.size();
 		super.addPseudoBoolean(lits, coefs, false, BigInteger
 				.valueOf(counter - 1));
 	}
 
 }