org.logicng.cardinalityconstraints.CCTotalizer 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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// Licensed under the Apache License, Version 2.0 (the "License"); //
// you may not use this file except in compliance with the License. //
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// http://www.apache.org/licenses/LICENSE-2.0 //
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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
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package org.logicng.cardinalityconstraints;
import org.logicng.collections.LNGVector;
import org.logicng.datastructures.EncodingResult;
import org.logicng.formulas.Variable;
/**
* Totalizer due to Bailleux and Boufkhad.
* @version 2.0.0
* @since 1.0
*/
public final class CCTotalizer {
private enum Bound {LOWER, UPPER, BOTH}
private LNGVector cardinalityInvars;
private EncodingResult result;
private CCIncrementalData incData;
/**
* Constructs a new totalizer.
*/
CCTotalizer() {
// intentionally left empty
}
/**
* Builds an at-most-k constraint.
* @param result the result
* @param vars the variables
* @param rhs the right-hand side
* @throws IllegalArgumentException if the right-hand side of the constraint was negative
*/
void buildAMK(final EncodingResult result, final Variable[] vars, final int rhs) {
final LNGVector cardinalityOutvars = this.initializeConstraint(result, vars);
this.incData = new CCIncrementalData(result, CCConfig.AMK_ENCODER.TOTALIZER, rhs, cardinalityOutvars);
this.toCNF(cardinalityOutvars, rhs, Bound.UPPER);
assert this.cardinalityInvars.size() == 0;
for (int i = rhs; i < cardinalityOutvars.size(); i++) {
this.result.addClause(cardinalityOutvars.get(i).negate());
}
}
/**
* Builds an at-least-k constraint.
* @param result the result
* @param vars the variables
* @param rhs the right-hand side
* @throws IllegalArgumentException if the right-hand side of the constraint was negative
*/
void buildALK(final EncodingResult result, final Variable[] vars, final int rhs) {
final LNGVector cardinalityOutvars = this.initializeConstraint(result, vars);
this.incData = new CCIncrementalData(result, CCConfig.ALK_ENCODER.TOTALIZER, rhs, vars.length, cardinalityOutvars);
this.toCNF(cardinalityOutvars, rhs, Bound.LOWER);
assert this.cardinalityInvars.size() == 0;
for (int i = 0; i < rhs; i++) {
this.result.addClause(cardinalityOutvars.get(i));
}
}
/**
* Builds an exactly-k constraint.
* @param vars the variables
* @param rhs the right-hand side
* @throws IllegalArgumentException if the right-hand side of the constraint was negative
*/
void buildEXK(final EncodingResult result, final Variable[] vars, final int rhs) {
final LNGVector cardinalityOutvars = this.initializeConstraint(result, vars);
this.toCNF(cardinalityOutvars, rhs, Bound.BOTH);
assert this.cardinalityInvars.size() == 0;
for (int i = 0; i < rhs; i++) {
this.result.addClause(cardinalityOutvars.get(i));
}
for (int i = rhs; i < cardinalityOutvars.size(); i++) {
this.result.addClause(cardinalityOutvars.get(i).negate());
}
}
/**
* Initializes the constraint.
* @param vars the variables
* @return the auxiliary variables
*/
private LNGVector initializeConstraint(final EncodingResult result, final Variable[] vars) {
result.reset();
this.result = result;
this.cardinalityInvars = new LNGVector<>(vars.length);
final LNGVector cardinalityOutvars = new LNGVector<>(vars.length);
for (final Variable var : vars) {
this.cardinalityInvars.push(var);
cardinalityOutvars.push(this.result.newVariable());
}
return cardinalityOutvars;
}
/**
* Returns the incremental data for the current encoded constraint.
* @return the incremental data for the current encoded constraint
*/
CCIncrementalData incrementalData() {
return this.incData;
}
private void toCNF(final LNGVector vars, final int rhs, final Bound bound) {
final LNGVector left = new LNGVector<>();
final LNGVector right = new LNGVector<>();
assert vars.size() > 1;
final int split = vars.size() / 2;
for (int i = 0; i < vars.size(); i++) {
if (i < split) {
if (split == 1) {
assert this.cardinalityInvars.size() > 0;
left.push(this.cardinalityInvars.back());
this.cardinalityInvars.pop();
} else {
left.push(this.result.newVariable());
}
} else {
if (vars.size() - split == 1) {
assert this.cardinalityInvars.size() > 0;
right.push(this.cardinalityInvars.back());
this.cardinalityInvars.pop();
} else {
right.push(this.result.newVariable());
}
}
}
if (bound == Bound.UPPER || bound == Bound.BOTH) {
this.adderAMK(left, right, vars, rhs);
}
if (bound == Bound.LOWER || bound == Bound.BOTH) {
this.adderALK(left, right, vars);
}
if (left.size() > 1) {
this.toCNF(left, rhs, bound);
}
if (right.size() > 1) {
this.toCNF(right, rhs, bound);
}
}
private void adderAMK(final LNGVector left, final LNGVector right,
final LNGVector output, final int rhs) {
assert output.size() == left.size() + right.size();
for (int i = 0; i <= left.size(); i++) {
for (int j = 0; j <= right.size(); j++) {
if (i == 0 && j == 0) {
continue;
}
if (i + j > rhs + 1) {
continue;
}
if (i == 0) {
this.result.addClause(right.get(j - 1).negate(), output.get(j - 1));
} else if (j == 0) {
this.result.addClause(left.get(i - 1).negate(), output.get(i - 1));
} else {
this.result.addClause(left.get(i - 1).negate(), right.get(j - 1).negate(), output.get(i + j - 1));
}
}
}
}
private void adderALK(final LNGVector left, final LNGVector right,
final LNGVector output) {
assert output.size() == left.size() + right.size();
for (int i = 0; i <= left.size(); i++) {
for (int j = 0; j <= right.size(); j++) {
if (i == 0 && j == 0) {
continue;
}
if (i == 0) {
this.result.addClause(right.get(j - 1), output.get(left.size() + j - 1).negate());
} else if (j == 0) {
this.result.addClause(left.get(i - 1), output.get(right.size() + i - 1).negate());
} else {
this.result.addClause(left.get(i - 1), right.get(j - 1), output.get(i + j - 2).negate());
}
}
}
}
@Override
public String toString() {
return this.getClass().getSimpleName();
}
}