Adds two randomized equivalence oracles based on the W method

eqtests/basic-eqtests/src/main/java/de/learnlib/eqtests/basic/RandomWMethodEQOracle.java

@@ -0,0 +1,129 @@
+package de.learnlib.eqtests.basic;
+
+import de.learnlib.api.EquivalenceOracle;
+import de.learnlib.api.MembershipOracle;
+import de.learnlib.oracles.DefaultQuery;
+import net.automatalib.automata.UniversalDeterministicAutomaton;
+import net.automatalib.automata.concepts.Output;
+import net.automatalib.util.automata.Automata;
+import net.automatalib.words.Word;
+import net.automatalib.words.WordBuilder;
+
+import javax.annotation.ParametersAreNonnullByDefault;
+import java.util.*;
+
+/**
+ * Implements an equivalence test by applying the W-method test on the given hypothesis automaton.
+ * Generally the Wp-method performs better in finding counter examples.
+ * Instead of enumerating the test suite in order, this is a sampling implementation:
+ * 1. sample uniformly from the states for a prefix
+ * 2. sample geometrically a random word
+ * 3. sample a word from the set of suffixes / state identifiers
+ * There are two parameters: minimalSize determines the minimal size of the random word, this is
+ * useful when one first performs a W(p)-method with some depth and continue with this randomized
+ * tester from that depth onward. The second parameter rndLength determines the expected length
+ * of the random word. (The expected length in effect is minimalSize + rndLength.)
+ * In the unbounded case it will not terminate for a correct hypothesis.
+ *
+ * @param <A> automaton type
+ * @param <I> input symbol type
+ * @param <D> output domain type
+ * @author Joshua Moerman
+ */
+public class RandomWMethodEQOracle<A extends UniversalDeterministicAutomaton<?, I, ?, ?, ?> & Output<I, D>, I, D>
+        implements EquivalenceOracle<A, I, D> {
+    private final MembershipOracle<I, D> sulOracle;
+    private final int minimalSize;
+    private final int rndLength;
+    private final int bound;
+
+    /**
+     * Constructor for an unbounded testing oracle
+     *
+     * @param sulOracle   oracle which answers tests.
+     * @param minimalSize minimal size of the random word
+     * @param rndLength   expected length (in addition to minimalSize) of random word
+     */
+    public RandomWMethodEQOracle(MembershipOracle<I, D> sulOracle, int minimalSize, int rndLength) {
+        this.sulOracle = sulOracle;
+        this.minimalSize = minimalSize;
+        this.rndLength = rndLength;
+        this.bound = 0;
+    }
+
+    /**
+     * Constructor for a bounded testing oracle
+     *
+     * @param sulOracle   oracle which answers tests.
+     * @param minimalSize minimal size of the random word
+     * @param rndLength   expected length (in addition to minimalSize) of random word
+     * @param bound       specifies the bound (set to 0 for unbounded).
+     */
+    public RandomWMethodEQOracle(MembershipOracle<I, D> sulOracle, int minimalSize, int rndLength, int bound) {
+        this.sulOracle = sulOracle;
+        this.minimalSize = minimalSize;
+        this.rndLength = rndLength;
+        this.bound = bound;
+    }
+
+    /*
+     * (non-Javadoc)
+     * @see de.learnlib.api.EquivalenceOracle#findCounterExample(java.lang.Object, java.util.Collection)
+     */
+    @Override
+    @ParametersAreNonnullByDefault
+    public DefaultQuery<I, D> findCounterExample(A hypothesis, Collection<? extends I> inputs) {
+        UniversalDeterministicAutomaton<?, I, ?, ?, ?> aut = hypothesis;
+        Output<I, D> out = hypothesis;
+        return doFindCounterExample(aut, out, inputs);
+    }
+
+    /*
+     * Delegate target, used to bind the state-parameter of the automaton
+     */
+    private <S> DefaultQuery<I, D> doFindCounterExample(UniversalDeterministicAutomaton<S, I, ?, ?, ?> hypothesis,
+                                                        Output<I, D> output, Collection<? extends I> inputs) {
+        // Note that we want to use ArrayLists because we want constant time random access
+        // We will sample from this for a prefix
+        ArrayList<Word<I>> stateCover = new ArrayList<>(hypothesis.size());
+        Automata.cover(hypothesis, inputs, stateCover, null);
+
+        // Then repeatedly from this for a random word
+        ArrayList<I> arrayAlphabet = new ArrayList<>(inputs);
+
+        // Finally we test the state with a suffix
+        ArrayList<Word<I>> globalSuffixes = new ArrayList<>();
+        Automata.characterizingSet(hypothesis, inputs, globalSuffixes);
+
+        Random rand = new Random();
+        int currentBound = bound;
+        while (bound == 0 || currentBound-- > 0) {
+            WordBuilder<I> wb = new WordBuilder<>(minimalSize + rndLength + 1);
+
+            // pick a random state
+            wb.append(stateCover.get(rand.nextInt(stateCover.size())));
+
+            // construct random middle part (of some expected length)
+            int size = minimalSize;
+            while ((size > 0) || (rand.nextDouble() > 1 / (rndLength + 1.0))) {
+                wb.append(arrayAlphabet.get(rand.nextInt(arrayAlphabet.size())));
+                if (size > 0) size--;
+            }
+
+            // pick a random suffix for this state
+            if (!globalSuffixes.isEmpty()) {
+                wb.append(globalSuffixes.get(rand.nextInt(globalSuffixes.size())));
+            }
+
+            Word<I> queryWord = wb.toWord();
+            DefaultQuery<I, D> query = new DefaultQuery<>(queryWord);
+            D hypOutput = output.computeOutput(queryWord);
+            sulOracle.processQueries(Collections.singleton(query));
+            if (!Objects.equals(hypOutput, query.getOutput()))
+                return query;
+        }
+
+        // no counter example found within the bound
+        return null;
+    }
+}

eqtests/basic-eqtests/src/main/java/de/learnlib/eqtests/basic/RandomWpMethodEQOracle.java

@@ -0,0 +1,148 @@
+package de.learnlib.eqtests.basic;
+
+import de.learnlib.api.EquivalenceOracle;
+import de.learnlib.api.MembershipOracle;
+import de.learnlib.oracles.DefaultQuery;
+import net.automatalib.automata.UniversalDeterministicAutomaton;
+import net.automatalib.automata.concepts.Output;
+import net.automatalib.commons.util.mappings.MutableMapping;
+import net.automatalib.util.automata.Automata;
+import net.automatalib.words.Word;
+import net.automatalib.words.WordBuilder;
+
+import javax.annotation.ParametersAreNonnullByDefault;
+import java.util.*;
+
+/**
+ * Implements an equivalence test by applying the Wp-method test on the given hypothesis automaton,
+ * as described in "Test Selection Based on Finite State Models" by S. Fujiwara et al.
+ * Instead of enumerating the test suite in order, this is a sampling implementation:
+ * 1. sample uniformly from the states for a prefix
+ * 2. sample geometrically a random word
+ * 3. sample a word from the set of suffixes / state identifiers (either local or global)
+ * There are two parameters: minimalSize determines the minimal size of the random word, this is
+ * useful when one first performs a W(p)-method with some depth and continue with this randomized
+ * tester from that depth onward. The second parameter rndLength determines the expected length
+ * of the random word. (The expected length in effect is minimalSize + rndLength.)
+ * In the unbounded case it will not terminate for a correct hypothesis.
+ *
+ * @param <A> automaton type
+ * @param <I> input symbol type
+ * @param <D> output domain type
+ * @author Joshua Moerman
+ */
+public class RandomWpMethodEQOracle<A extends UniversalDeterministicAutomaton<?, I, ?, ?, ?> & Output<I, D>, I, D>
+        implements EquivalenceOracle<A, I, D> {
+    private final MembershipOracle<I, D> sulOracle;
+    private final int minimalSize;
+    private final int rndLength;
+    private final int bound;
+
+    /**
+     * Constructor for an unbounded testing oracle
+     *
+     * @param sulOracle   oracle which answers tests.
+     * @param minimalSize minimal size of the random word
+     * @param rndLength   expected length (in addition to minimalSize) of random word
+     */
+    public RandomWpMethodEQOracle(MembershipOracle<I, D> sulOracle, int minimalSize, int rndLength) {
+        this.sulOracle = sulOracle;
+        this.minimalSize = minimalSize;
+        this.rndLength = rndLength;
+        this.bound = 0;
+    }
+
+    /**
+     * Constructor for a bounded testing oracle
+     *
+     * @param sulOracle   oracle which answers tests.
+     * @param minimalSize minimal size of the random word
+     * @param rndLength   expected length (in addition to minimalSize) of random word
+     * @param bound       specifies the bound (set to 0 for unbounded).
+     */
+    public RandomWpMethodEQOracle(MembershipOracle<I, D> sulOracle, int minimalSize, int rndLength, int bound) {
+        this.sulOracle = sulOracle;
+        this.minimalSize = minimalSize;
+        this.rndLength = rndLength;
+        this.bound = bound;
+    }
+
+    /*
+     * (non-Javadoc)
+     * @see de.learnlib.api.EquivalenceOracle#findCounterExample(java.lang.Object, java.util.Collection)
+     */
+    @Override
+    @ParametersAreNonnullByDefault
+    public DefaultQuery<I, D> findCounterExample(A hypothesis, Collection<? extends I> inputs) {
+        UniversalDeterministicAutomaton<?, I, ?, ?, ?> aut = hypothesis;
+        Output<I, D> out = hypothesis;
+        return doFindCounterExample(aut, out, inputs);
+    }
+
+    /*
+     * Delegate target, used to bind the state-parameter of the automaton
+     */
+    private <S> DefaultQuery<I, D> doFindCounterExample(UniversalDeterministicAutomaton<S, I, ?, ?, ?> hypothesis,
+                                                        Output<I, D> output, Collection<? extends I> inputs) {
+        // Note that we want to use ArrayLists because we want constant time random access
+        // We will sample from this for a prefix
+        ArrayList<Word<I>> stateCover = new ArrayList<>(hypothesis.size());
+        Automata.cover(hypothesis, inputs, stateCover, null);
+
+        // Then repeatedly from this for a random word
+        ArrayList<I> arrayAlphabet = new ArrayList<>(inputs);
+
+        // Finally we test the state with a suffix, sometimes a global one, sometimes local
+        ArrayList<Word<I>> globalSuffixes = new ArrayList<>();
+        Automata.characterizingSet(hypothesis, inputs, globalSuffixes);
+
+        MutableMapping<S, ArrayList<Word<I>>> localSuffixSets = hypothesis.createStaticStateMapping();
+        for (S state : hypothesis.getStates()) {
+            ArrayList<Word<I>> suffixSet = new ArrayList<>();
+            Automata.stateCharacterizingSet(hypothesis, inputs, state, suffixSet);
+            localSuffixSets.put(state, suffixSet);
+        }
+
+        Random rand = new Random();
+        int currentBound = bound;
+        while (bound == 0 || currentBound-- > 0) {
+            WordBuilder<I> wb = new WordBuilder<>(minimalSize + rndLength + 1);
+
+            // pick a random state
+            wb.append(stateCover.get(rand.nextInt(stateCover.size())));
+
+            // construct random middle part (of some expected length)
+            int size = minimalSize;
+            while ((size > 0) || (rand.nextDouble() > 1 / (rndLength + 1.0))) {
+                wb.append(arrayAlphabet.get(rand.nextInt(arrayAlphabet.size())));
+                if (size > 0) size--;
+            }
+
+            // pick a random suffix for this state
+            // 50% chance for state testing, 50% chance for transition testing
+            if (rand.nextBoolean()) {
+                // global
+                if (!globalSuffixes.isEmpty()) {
+                    wb.append(globalSuffixes.get(rand.nextInt(globalSuffixes.size())));
+                }
+            } else {
+                // local
+                S state2 = hypothesis.getState(wb);
+                ArrayList<Word<I>> localSuffixes = localSuffixSets.get(state2);
+                if (!localSuffixes.isEmpty()) {
+                    wb.append(localSuffixes.get(rand.nextInt(localSuffixes.size())));
+                }
+            }
+
+            Word<I> queryWord = wb.toWord();
+            DefaultQuery<I, D> query = new DefaultQuery<>(queryWord);
+            D hypOutput = output.computeOutput(queryWord);
+            sulOracle.processQueries(Collections.singleton(query));
+            if (!Objects.equals(hypOutput, query.getOutput()))
+                return query;
+        }
+
+        // no counter example found within the bound
+        return null;
+    }
+}