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Commander encoding for AMO constraints
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src/main/java/org/logicng/cardinalityconstraints/CCAMOCommander.java
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| /////////////////////////////////////////////////////////////////////////// | ||
| // __ _ _ ________ // | ||
| // / / ____ ____ _(_)____/ | / / ____/ // | ||
| // / / / __ \/ __ `/ / ___/ |/ / / __ // | ||
| // / /___/ /_/ / /_/ / / /__/ /| / /_/ / // | ||
| // /_____/\____/\__, /_/\___/_/ |_/\____/ // | ||
| // /____/ // | ||
| // // | ||
| // The Next Generation Logic Library // | ||
| // // | ||
| /////////////////////////////////////////////////////////////////////////// | ||
| // // | ||
| // Copyright 2015-2016 Christoph Zengler // | ||
| // // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); // | ||
| // you may not use this file except in compliance with the License. // | ||
| // You may obtain a copy of the License at // | ||
| // // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 // | ||
| // // | ||
| // Unless required by applicable law or agreed to in writing, software // | ||
| // distributed under the License is distributed on an "AS IS" BASIS, // | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or // | ||
| // implied. See the License for the specific language governing // | ||
| // permissions and limitations under the License. // | ||
| // // | ||
| /////////////////////////////////////////////////////////////////////////// | ||
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| /** | ||
| * PBLib -- Copyright (c) 2012-2013 Peter Steinke | ||
| * | ||
| * 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 COPYRIGHT HOLDERS BE | ||
| * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION | ||
| * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION | ||
| * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | ||
| */ | ||
|
|
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| package org.logicng.cardinalityconstraints; | ||
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| import org.logicng.collections.ImmutableFormulaList; | ||
| import org.logicng.collections.LNGVector; | ||
| import org.logicng.formulas.FType; | ||
| import org.logicng.formulas.Formula; | ||
| import org.logicng.formulas.FormulaFactory; | ||
| import org.logicng.formulas.Literal; | ||
| import org.logicng.formulas.Variable; | ||
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|
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| import java.util.ArrayList; | ||
| import java.util.List; | ||
|
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| /** | ||
| * Encodes that at most one variable is assigned value true. Uses the commander encoding due to Klieber & Kwon. | ||
| * @version 1.1 | ||
| * @since 1.1 | ||
| */ | ||
| public final class CCAMOCommander extends CCAtMostOne { | ||
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| private final FormulaFactory f; | ||
| private List<Formula> result; | ||
| private int k; | ||
| private LNGVector<Literal> literals; | ||
| private LNGVector<Literal> nextLiterals; | ||
| private LNGVector<Literal> currentLiterals; | ||
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| /** | ||
| * Constructs the commander AMO encoder. | ||
| * @param f the formula factory | ||
| * @param k the group size for the encoding | ||
| */ | ||
| public CCAMOCommander(final FormulaFactory f, int k) { | ||
| this.f = f; | ||
| this.k = k; | ||
| this.result = new ArrayList<>(); | ||
| this.literals = new LNGVector<>(); | ||
| this.nextLiterals = new LNGVector<>(); | ||
| this.currentLiterals = new LNGVector<>(); | ||
| } | ||
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| /** | ||
| * Constructs the commander AMO encoder. | ||
| * @param f the formula factory | ||
| */ | ||
| public CCAMOCommander(final FormulaFactory f) { | ||
| this(f, 3); | ||
| } | ||
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| @Override | ||
| public ImmutableFormulaList build(final Variable... vars) { | ||
| this.result.clear(); | ||
| if (vars.length <= 0) | ||
| return new ImmutableFormulaList(FType.AND, this.result); | ||
| this.currentLiterals.clear(); | ||
| this.nextLiterals.clear(); | ||
| for (final Variable var : vars) | ||
| this.currentLiterals.push(var); | ||
| this.encodeRecursive(); | ||
| return new ImmutableFormulaList(FType.AND, this.result); | ||
| } | ||
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| /** | ||
| * Internal recursive encoding. | ||
| */ | ||
| private void encodeRecursive() { | ||
| boolean isExactlyOne = false; | ||
| while (this.currentLiterals.size() > this.k) { | ||
| this.literals.clear(); | ||
| this.nextLiterals.clear(); | ||
| for (int i = 0; i < this.currentLiterals.size(); i++) { | ||
| this.literals.push(this.currentLiterals.get(i)); | ||
| if (i % this.k == this.k - 1 || i == this.currentLiterals.size() - 1) { | ||
| this.encodeNonRecursive(this.literals); | ||
| this.literals.push(this.f.newCCVariable()); | ||
| this.nextLiterals.push(this.literals.back().negate()); | ||
| if (isExactlyOne && this.literals.size() > 0) | ||
| this.result.add(this.vec2clause(this.literals)); | ||
| for (int j = 0; j < this.literals.size() - 1; j++) | ||
| this.result.add(this.f.clause(this.literals.back().negate(), this.literals.get(j).negate())); | ||
| this.literals.clear(); | ||
| } | ||
| } | ||
| this.currentLiterals.replaceInplace(this.nextLiterals); | ||
| isExactlyOne = true; | ||
| } | ||
| this.encodeNonRecursive(this.currentLiterals); | ||
| if (isExactlyOne && this.currentLiterals.size() > 0) | ||
| this.result.add(this.vec2clause(this.currentLiterals)); | ||
| } | ||
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| /** | ||
| * Internal non recursive encoding. | ||
| * @param literals the current literals | ||
| */ | ||
| private void encodeNonRecursive(final LNGVector<Literal> literals) { | ||
| if (literals.size() > 1) | ||
| for (int i = 0; i < literals.size(); i++) | ||
| for (int j = i + 1; j < literals.size(); j++) | ||
| this.result.add(this.f.clause(literals.get(i).negate(), literals.get(j).negate())); | ||
| } | ||
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| /** | ||
| * Returns a clause for a vector of literals. | ||
| * @param literals the literals | ||
| * @return the clause | ||
| */ | ||
| private Formula vec2clause(final LNGVector<Literal> literals) { | ||
| final List<Literal> lits = new ArrayList<>(literals.size()); | ||
| for (final Literal l : literals) | ||
| lits.add(l); | ||
| return this.f.clause(lits); | ||
| } | ||
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| @Override | ||
| public String toString() { | ||
| return this.getClass().getSimpleName(); | ||
| } | ||
| } |
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