org.logicng.formulas.ExtendedFormulaFactory Maven / Gradle / Ivy
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// The Next Generation Logic Library //
// //
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// //
// Copyright 2015-20xx 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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package org.logicng.formulas;
import org.logicng.collections.LNGIntVector;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
/**
* An extended version of the formula factory that allows saving and loading states to reduce memory usage.
*
* New formulas can only be generated by a formula factory. It is implemented s.t. it is guaranteed that equivalent
* formulas (in terms of associativity and commutativity) are hold exactly once in memory.
*
* A formula factory is NOT thread-safe. If you generate formulas from more than one thread you either need to
* synchronize the formula factory yourself or you use a formula factory for each single thread.
* @version 2.3.2
* @since 1.2
*/
public class ExtendedFormulaFactory extends FormulaFactory {
private final LNGIntVector validStates = new LNGIntVector();
private int nextStateId;
/**
* Shrinks a given map to a given size
* @param map the map to be shrunk
* @param newSize the new size, the map shall be shrunk to
*/
static void shrinkMap(final Map map, final int newSize) {
if (!(map instanceof LinkedHashMap)) {
throw new IllegalStateException("Cannot shrink a map which is not of type LinkedHashMap");
}
if (newSize > map.size()) {
throw new IllegalStateException("Cannot shrink a map of size " + map.size() + " to new size " + newSize);
}
final Iterator> entryIterator = map.entrySet().iterator();
int count = 0;
while (count < newSize) {
entryIterator.next();
count++;
}
while (entryIterator.hasNext()) {
entryIterator.next();
entryIterator.remove();
}
}
/**
* Shrinks a given set to a given size
* @param set the set to be shrunk
* @param newSize the new size, the set shall be shrunk to
*/
static void shrinkSet(final Set set, final int newSize) {
if (!(set instanceof LinkedHashSet)) {
throw new IllegalStateException("Cannot shrink a set which is not of type LinkedHashSet");
}
if (newSize > set.size()) {
throw new IllegalStateException("Cannot shrink a set of size " + set.size() + " to new size " + newSize);
}
final Iterator entryIterator = set.iterator();
int count = 0;
while (count < newSize) {
entryIterator.next();
count++;
}
while (entryIterator.hasNext()) {
entryIterator.next();
entryIterator.remove();
}
}
@Override
public void clear() {
this.posLiterals = new LinkedHashMap<>();
this.negLiterals = new LinkedHashMap<>();
this.generatedVariables = new LinkedHashSet<>();
this.nots = new LinkedHashMap<>();
this.implications = new LinkedHashMap<>();
this.equivalences = new LinkedHashMap<>();
this.ands2 = new LinkedHashMap<>();
this.ands3 = new LinkedHashMap<>();
this.ands4 = new LinkedHashMap<>();
this.andsN = new LinkedHashMap<>();
this.ors2 = new LinkedHashMap<>();
this.ors3 = new LinkedHashMap<>();
this.ors4 = new LinkedHashMap<>();
this.orsN = new LinkedHashMap<>();
this.pbConstraints = new LinkedHashMap<>();
this.cardinalityConstraints = new LinkedHashMap<>();
this.ccCounter = 0;
this.pbCounter = 0;
this.cnfCounter = 0;
this.transformationCache = new HashMap<>();
this.predicateCache = new HashMap<>();
this.functionCache = new HashMap<>();
this.pbEncodingCache = new HashMap<>();
}
/**
* Saves the FormulaFactoryState to be loaded later.
* @return the FormulaFactoryState.
*/
public FormulaFactoryState save() {
final int[] state = new int[19];
state[0] = this.posLiterals.size();
state[1] = this.negLiterals.size();
state[2] = this.generatedVariables.size();
state[3] = this.nots.size();
state[4] = this.implications.size();
state[5] = this.equivalences.size();
state[6] = this.ands2.size();
state[7] = this.ands3.size();
state[8] = this.ands4.size();
state[9] = this.andsN.size();
state[10] = this.ors2.size();
state[11] = this.ors3.size();
state[12] = this.ors4.size();
state[13] = this.orsN.size();
state[14] = this.pbConstraints.size();
state[15] = this.cardinalityConstraints.size();
state[16] = this.ccCounter;
state[17] = this.pbCounter;
state[18] = this.cnfCounter;
final int id = this.nextStateId++;
this.validStates.push(id);
return new FormulaFactoryState(id, state);
}
/**
* Loads a previously saved FormulaFactoryState. All formula factory states saved after the loaded one become invalid.
* @param state the FormulaFactoryState to be loaded
* @throws IllegalArgumentException if the FormulaFactoryState to be loaded is invalid
*/
public void load(final FormulaFactoryState state) {
int index = -1;
for (int i = this.validStates.size() - 1; i >= 0 && index == -1; i--) {
if (this.validStates.get(i) == state.id()) {
index = i;
}
}
if (index == -1) {
throw new IllegalArgumentException("The given formula factory state is not valid anymore.");
}
this.validStates.shrinkTo(index + 1);
shrinkMap(this.posLiterals, state.state()[0]);
shrinkMap(this.negLiterals, state.state()[1]);
shrinkSet(this.generatedVariables, state.state()[2]);
shrinkMap(this.nots, state.state()[3]);
shrinkMap(this.implications, state.state()[4]);
shrinkMap(this.equivalences, state.state()[5]);
shrinkMap(this.ands2, state.state()[6]);
shrinkMap(this.ands3, state.state()[7]);
shrinkMap(this.ands4, state.state()[8]);
shrinkMap(this.andsN, state.state()[9]);
shrinkMap(this.ors2, state.state()[10]);
shrinkMap(this.ors3, state.state()[11]);
shrinkMap(this.ors4, state.state()[12]);
shrinkMap(this.orsN, state.state()[13]);
shrinkMap(this.pbConstraints, state.state()[14]);
shrinkMap(this.cardinalityConstraints, state.state()[15]);
this.ccCounter = state.state()[16];
this.pbCounter = state.state()[17];
this.cnfCounter = state.state()[18];
clearCaches();
}
/**
* Clears the transformation, function, and PB encoding caches.
*/
public void clearCaches() {
this.transformationCache.clear();
this.functionCache.clear();
this.pbEncodingCache.clear();
}
}