org.logicng.solvers.maxsat.encodings.Ladder Maven / Gradle / Ivy
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// The Next Generation Logic Library //
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// Copyright 2015-20xx Christoph Zengler //
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/*
* Open-WBO -- Copyright (c) 2013-2015, Ruben Martins, Vasco Manquinho, Ines Lynce
*
* 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
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package org.logicng.solvers.maxsat.encodings;
import static org.logicng.solvers.sat.MiniSatStyleSolver.mkLit;
import static org.logicng.solvers.sat.MiniSatStyleSolver.not;
import org.logicng.collections.LNGIntVector;
import org.logicng.solvers.maxsat.algorithms.MaxSAT;
import org.logicng.solvers.sat.MiniSatStyleSolver;
/**
* Encodes that exactly one literal from 'lits' is assigned value true. Uses the Ladder/Regular encoding for
* translating the AMO constraint into CNF.
* @version 2.0.0
* @since 1.0
*/
public class Ladder extends Encoding {
/**
* Encodes and adds the AMO constraint to the given solver.
* @param s the solver
* @param lits the literals for the constraint
*/
public void encode(final MiniSatStyleSolver s, final LNGIntVector lits) {
assert lits.size() != 0;
if (lits.size() == 1) {
addUnitClause(s, lits.get(0));
} else {
final LNGIntVector seqAuxiliary = new LNGIntVector();
for (int i = 0; i < lits.size() - 1; i++) {
seqAuxiliary.push(mkLit(s.nVars(), false));
MaxSAT.newSATVariable(s);
}
for (int i = 0; i < lits.size(); i++) {
if (i == 0) {
addBinaryClause(s, lits.get(i), not(seqAuxiliary.get(i)));
addBinaryClause(s, not(lits.get(i)), seqAuxiliary.get(i));
} else if (i == lits.size() - 1) {
addBinaryClause(s, lits.get(i), seqAuxiliary.get(i - 1));
addBinaryClause(s, not(lits.get(i)), not(seqAuxiliary.get(i - 1)));
} else {
addBinaryClause(s, not(seqAuxiliary.get(i - 1)), seqAuxiliary.get(i));
addTernaryClause(s, lits.get(i), not(seqAuxiliary.get(i)), seqAuxiliary.get(i - 1));
addBinaryClause(s, not(lits.get(i)), seqAuxiliary.get(i));
addBinaryClause(s, not(lits.get(i)), not(seqAuxiliary.get(i - 1)));
}
}
}
}
@Override
public String toString() {
return this.getClass().getSimpleName();
}
}