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A collection of equivalence oracles
/* Copyright (C) 2013-2020 TU Dortmund
* This file is part of LearnLib, http://www.learnlib.de/.
*
* 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.
*/
package de.learnlib.oracle.equivalence.vpda;
import java.util.Collection;
import java.util.Random;
import java.util.stream.Stream;
import com.google.common.base.Preconditions;
import de.learnlib.api.oracle.MembershipOracle;
import de.learnlib.oracle.equivalence.AbstractTestWordEQOracle;
import net.automatalib.automata.concepts.Output;
import net.automatalib.words.VPDAlphabet;
import net.automatalib.words.Word;
import net.automatalib.words.WordBuilder;
/**
* An equivalence oracle based on the generation of random (well-matched) words.
*
* @param
* input symbol type
*
* @author Malte Isberner
*/
public class RandomWellMatchedWordsEQOracle extends AbstractTestWordEQOracle, I, Boolean> {
private final Random random;
private final double callProb;
private final int maxTests, minLength, maxLength;
public RandomWellMatchedWordsEQOracle(final Random random,
final MembershipOracle oracle,
final double callProb,
final int maxTests,
final int minLength,
final int maxLength) {
this(random, oracle, callProb, maxTests, minLength, maxLength, 1);
}
public RandomWellMatchedWordsEQOracle(final Random random,
final MembershipOracle oracle,
final double callProb,
final int maxTests,
final int minLength,
final int maxLength,
final int batchSize) {
super(oracle, batchSize);
Preconditions.checkArgument(minLength <= maxLength, "minLength is smaller than maxLength");
this.random = random;
this.callProb = callProb;
this.maxTests = maxTests;
this.minLength = minLength;
this.maxLength = maxLength;
}
@Override
protected Stream> generateTestWords(Output hypothesis, Collection inputs) {
if (!(inputs instanceof VPDAlphabet)) {
throw new IllegalArgumentException(
"In order to generate well-matched words, a structured alphabet is required");
}
@SuppressWarnings("unchecked")
final VPDAlphabet alphabet = (VPDAlphabet) inputs;
final int lengthRange = (maxLength - minLength) + 1;
return Stream.generate(() -> generateWellMatched(alphabet, minLength + random.nextInt(lengthRange)))
.limit(maxTests);
}
private Word generateWellMatched(VPDAlphabet alphabet, final int len) {
WordBuilder wb = new WordBuilder<>(len);
generateWellMatched(wb, alphabet, len);
return wb.toWord();
}
private void generateWellMatched(WordBuilder wb, VPDAlphabet alphabet, int length) {
if (length == 0) {
return;
}
if (length == 1) {
wb.append(alphabet.getInternalSymbol(random.nextInt(alphabet.getNumInternals())));
return;
}
double act = random.nextDouble();
if (act < callProb) {
boolean dir = random.nextBoolean();
if (dir) {
final int cpos = random.nextInt(length - 1);
generateWellMatched(wb, alphabet, cpos);
wb.append(alphabet.getCallSymbol(random.nextInt(alphabet.getNumCalls())));
final int rpos = cpos + 1 + random.nextInt(length - cpos - 1);
generateWellMatched(wb, alphabet, rpos - cpos - 1);
wb.append(alphabet.getReturnSymbol(random.nextInt(alphabet.getNumReturns())));
generateWellMatched(wb, alphabet, length - rpos - 1);
} else {
final int rpos = 1 + random.nextInt(length - 1);
final int cpos = random.nextInt(rpos);
generateWellMatched(wb, alphabet, cpos);
wb.append(alphabet.getCallSymbol(random.nextInt(alphabet.getNumCalls())));
generateWellMatched(wb, alphabet, rpos - cpos - 1);
wb.append(alphabet.getReturnSymbol(random.nextInt(alphabet.getNumReturns())));
generateWellMatched(wb, alphabet, length - rpos - 1);
}
} else {
final int sep = 1 + random.nextInt(length - 1);
generateWellMatched(wb, alphabet, sep);
generateWellMatched(wb, alphabet, length - sep);
}
}
}