Package solver.constraints.binary

Source Code of solver.constraints.binary.PropLessOrEqualXY_C

/*
* Copyright (c) 1999-2014, Ecole des Mines de Nantes
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*     * Redistributions in binary form must reproduce the above copyright
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*       derived from this software without specific prior written permission.
*
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package solver.constraints.binary;

import gnu.trove.map.hash.THashMap;
import solver.Solver;
import solver.constraints.Propagator;
import solver.constraints.PropagatorPriority;
import solver.exception.ContradictionException;
import solver.explanations.Deduction;
import solver.explanations.Explanation;
import solver.explanations.VariableState;
import solver.variables.IntVar;
import solver.variables.Variable;
import solver.variables.events.IntEventType;
import util.ESat;

/**
* X + Y <= C
* <br/>
*
* @author Charles Prud'homme
* @since 13/06/12
*/
public final class PropLessOrEqualXY_C extends Propagator<IntVar> {

    final IntVar x;
    final IntVar y;
    final int cste;

    @SuppressWarnings({"unchecked"})
    public PropLessOrEqualXY_C(IntVar[] vars, int c) {
        super(vars, PropagatorPriority.BINARY, true);
        this.x = vars[0];
        this.y = vars[1];
        this.cste = c;
    }

    @Override
    public int getPropagationConditions(int vIdx) {
        return IntEventType.INSTANTIATE.getMask() + IntEventType.INCLOW.getMask();
    }

    @Override
    public void propagate(int evtmask) throws ContradictionException {
        x.updateUpperBound(this.cste - y.getLB(), aCause);
        y.updateUpperBound(this.cste - x.getLB(), aCause);
        if (x.getUB() + y.getUB() <= this.cste) {
            this.setPassive();
        }
    }

    @Override
    public void propagate(int idxVarInProp, int mask) throws ContradictionException {
        if (idxVarInProp == 0) {
            y.updateUpperBound(this.cste - x.getLB(), aCause);
        } else {
            x.updateUpperBound(this.cste - y.getLB(), aCause);
        }
        if (x.getUB() + y.getUB() <= this.cste) {
            this.setPassive();
        }
    }


    @Override
    public ESat isEntailed() {
        if (x.getLB() + y.getLB() > cste)
            return ESat.FALSE;
        else if (x.getUB() + y.getUB() <= this.cste)
            return ESat.TRUE;
        else
            return ESat.UNDEFINED;
    }

    @Override
    public String toString() {
        StringBuilder st = new StringBuilder();
        st.append(x.getName()).append(" + ").append(y.getName()).append(" <= ").append(cste);
        return st.toString();
    }

    @Override
    public void explain(Deduction d, Explanation e) {
        e.add(solver.getExplainer().getPropagatorActivation(this));
        e.add(aCause);
        // the current deduction is due to the current domain of the involved variables
        Variable var = d.getVar();
        if (var.equals(x)) {
            // a deduction has been made on x ; this is related to y only
            y.explain(VariableState.LB, e);
        } else if (var.equals(y)) {
            x.explain(VariableState.UB, e);
        } else {
            super.explain(d, e);
        }
    }

    @Override
    public void duplicate(Solver solver, THashMap<Object, Object> identitymap) {
        if (!identitymap.containsKey(this)) {
            this.vars[0].duplicate(solver, identitymap);
            IntVar X = (IntVar) identitymap.get(this.vars[0]);
            this.vars[1].duplicate(solver, identitymap);
            IntVar Y = (IntVar) identitymap.get(this.vars[1]);

            identitymap.put(this, new PropLessOrEqualXY_C(new IntVar[]{X, Y}, this.cste));
        }
    }
}
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