org.chocosolver.solver.constraints.extension.binary.CouplesBitSetTable Maven / Gradle / Ivy

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/*
 * This file is part of choco-solver, http://choco-solver.org/
 *
 * Copyright (c) 2024, IMT Atlantique. All rights reserved.
 *
 * Licensed under the BSD 4-clause license.
 *
 * See LICENSE file in the project root for full license information.
 */
package org.chocosolver.solver.constraints.extension.binary;

import org.chocosolver.solver.constraints.extension.Tuples;
import org.chocosolver.solver.variables.IntVar;

import java.util.BitSet;

/**
 * 

 *
 * @author Charles Prud'homme
 * @since 22/04/2014
 */
class CouplesBitSetTable extends BinRelation {

    /**
     * table[0][i] gives the supports of value i of variable 0
     * table[1][i] gives the supports of value i of variable 1
     */
    private final BitSet[][] table;

    /**
     * first value of x, and y
     */
    private final int[] offsets;

    /**
     * Create a tuple list for AC3bit+rm
     *
     * @param tuples list of tuples
     */
    public CouplesBitSetTable(Tuples tuples, IntVar var1, IntVar var2) {
        offsets = new int[]{var1.getLB(), var2.getLB()};
        int range1 = var1.getUB() - offsets[0] + 1;
        int range2 = var2.getUB() - offsets[1] + 1;
        this.table = new BitSet[2][];
        this.table[0] = new BitSet[range1];
        boolean feasible = tuples.isFeasible();
        for (int i = 0; i < range1; i++) {
            table[0][i] = new BitSet(range2);
            if (!feasible) table[0][i].set(0, range2);
        }
        this.table[1] = new BitSet[range2];
        for (int i = 0; i < range2; i++) {
            table[1][i] = new BitSet(range1);
            if (!feasible) table[1][i].set(0, range1);
        }

        int nt = tuples.nbTuples();
        for (int i = 0; i < nt; i++) {
            int[] tuple = tuples.get(i);
//            setCouple(tuple[0], tuple[1]);
            if (var1.contains(tuple[0]) && var2.contains(tuple[1])) {
                if (feasible) {
                    table[0][tuple[0] - offsets[0]].set(tuple[1] - offsets[1]);
                    table[1][tuple[1] - offsets[1]].set(tuple[0] - offsets[0]);
                } else {
                    table[0][tuple[0] - offsets[0]].clear(tuple[1] - offsets[1]);
                    table[1][tuple[1] - offsets[1]].clear(tuple[0] - offsets[0]);
                }
            }
        }
    }

    public boolean isConsistent(int x, int y) {
        return table[0][x - offsets[0]].get(y - offsets[1]);
    }

    public boolean checkCouple(int x, int y) {
        return table[0][x - offsets[0]].get(y - offsets[1]);
    }

	/**
     * checks if var=val has no support within the domain of v
     * @param var a variable index
     * @param val a value for var
     * @param v a variable
     * @return true iff there exists no support for v where var = val
     */
    public boolean checkUnsupportedValue(int var, int val, IntVar v) {
        int UB = v.getUB();
        BitSet _table = table[var][val - offsets[var]];
        int o = offsets[1 - var];
        for (int i = v.getLB(); i <= UB; i = v.nextValue(i)) {
            if (_table.get(i - o)) {
                return false;
            }
        }
        return true;
    }

    @Override
    public Tuples convert() {
        Tuples tuples = new Tuples(true);
        for(int i = 0; i < table[0].length; i++) {
            for (int b = table[0][i].nextSetBit(0); b > -1; b = table[0][i].nextSetBit(b + 1)) {
                tuples.add(i + offsets[0], b + offsets[1]);
            }
        }
        return tuples;
    }
}