Add checks for stable hypothesis constructions

CHANGELOG.md

@@ -17,10 +17,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * Statistics collection has received a major rework. Previously, classes would implement the `StatisticCollector` interface and return a `StatisticData` object which 1) only allows for describing a very limited amount of data, and 2) requires you to keep track of all the objects that collect data. This approach has been *replaced* by a new `StatisticsService`. Instances of this service can be obtained similar to a logger via `Statistics.getService()` and require you to provide an implementation of this service on the classpath (a default one is provided by the `learnlib-statistics` module). The new service allows arbitrary components to collect various data which can be conveniently extracted based on the new `StatisticsKey`s used by the components. For more details on advanced scenarios (such as multi-threaded benchmarking), see the documentation of the respective classes. While this may require you to adjust the way you are collecting statistics, all functionality from beforehand should still be available.
   * `SimpleProfiler` has been replaced by the new clock-based statistics.
 * The `generateTestWords` method of `AbstractTestWordEQOracle` now needs to be public.
+* The classes of `de.learnlib.testsupport.it.learner` have been split into the packages `de.learnlib.testsupport.it{,testcase,util,variant}` in the same module (`de.learnlib.testsupport:learnlib-learner-it-support`).
 
 ### Fixed
 
 * The `de.learnlib.algorithm.adt` module now correctly `exports` the `de.learnlib.algorithm.adt.config.model.*` packages.
+* The `TTTLambdaMealy` learner now returns stable hypotheses that no longer issue queries during traversal. 
 
 
 ## [0.18.0] - 2025-02-06

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/explicit/it/ExplicitAAARLearnerIdentityDFAIT.java

@@ -23,13 +23,18 @@
 import de.learnlib.algorithm.aaar.explicit.IdentityInitialAbstraction;
 import de.learnlib.algorithm.aaar.explicit.NoopIncrementor;
 import de.learnlib.oracle.MembershipOracle.DFAMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractDFALearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.DFALearnerVariantList;
+import de.learnlib.testsupport.it.AbstractDFALearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.DFALearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 
 public class ExplicitAAARLearnerIdentityDFAIT extends AbstractDFALearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I> void addLearnerVariants(Alphabet<I> alphabet,
                                           int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/explicit/it/ExplicitAAARLearnerIdentityMealyIT.java

@@ -23,14 +23,19 @@
 import de.learnlib.algorithm.aaar.explicit.IdentityInitialAbstraction;
 import de.learnlib.algorithm.aaar.explicit.NoopIncrementor;
 import de.learnlib.oracle.MembershipOracle.MealyMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMealyLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MealyLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMealyLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MealyLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 import net.automatalib.word.Word;
 
 public class ExplicitAAARLearnerIdentityMealyIT extends AbstractMealyLearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I, O> void addLearnerVariants(Alphabet<I> alphabet,
                                              int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/explicit/it/ExplicitAAARLearnerIdentityMooreIT.java

@@ -23,14 +23,19 @@
 import de.learnlib.algorithm.aaar.explicit.IdentityInitialAbstraction;
 import de.learnlib.algorithm.aaar.explicit.NoopIncrementor;
 import de.learnlib.oracle.MembershipOracle.MooreMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMooreLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MooreLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMooreLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MooreLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 import net.automatalib.word.Word;
 
 public class ExplicitAAARLearnerIdentityMooreIT extends AbstractMooreLearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I, O> void addLearnerVariants(Alphabet<I> alphabet,
                                              int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/explicit/it/ExplicitAAARLearnerModuloDFAIT.java

@@ -23,13 +23,18 @@
 import de.learnlib.algorithm.aaar.explicit.Incrementor;
 import de.learnlib.algorithm.aaar.explicit.ModuloInitialAbstraction;
 import de.learnlib.oracle.MembershipOracle.DFAMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractDFALearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.DFALearnerVariantList;
+import de.learnlib.testsupport.it.AbstractDFALearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.DFALearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 
 public class ExplicitAAARLearnerModuloDFAIT extends AbstractDFALearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I> void addLearnerVariants(Alphabet<I> alphabet,
                                           int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/explicit/it/ExplicitAAARLearnerModuloMealyIT.java

@@ -23,14 +23,19 @@
 import de.learnlib.algorithm.aaar.explicit.Incrementor;
 import de.learnlib.algorithm.aaar.explicit.ModuloInitialAbstraction;
 import de.learnlib.oracle.MembershipOracle.MealyMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMealyLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MealyLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMealyLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MealyLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 import net.automatalib.word.Word;
 
 public class ExplicitAAARLearnerModuloMealyIT extends AbstractMealyLearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I, O> void addLearnerVariants(Alphabet<I> alphabet,
                                              int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/explicit/it/ExplicitAAARLearnerModuloMooreIT.java

@@ -23,14 +23,19 @@
 import de.learnlib.algorithm.aaar.explicit.Incrementor;
 import de.learnlib.algorithm.aaar.explicit.ModuloInitialAbstraction;
 import de.learnlib.oracle.MembershipOracle.MooreMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMooreLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MooreLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMooreLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MooreLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 import net.automatalib.word.Word;
 
 public class ExplicitAAARLearnerModuloMooreIT extends AbstractMooreLearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I, O> void addLearnerVariants(Alphabet<I> alphabet,
                                              int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/generic/it/GenericAAARLearnerDFAIT.java

@@ -23,13 +23,18 @@
 import de.learnlib.algorithm.aaar.TranslatingLearnerWrapper;
 import de.learnlib.algorithm.aaar.generic.GenericAAARLearnerDFA;
 import de.learnlib.oracle.MembershipOracle.DFAMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractDFALearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.DFALearnerVariantList;
+import de.learnlib.testsupport.it.AbstractDFALearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.DFALearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 
 public class GenericAAARLearnerDFAIT extends AbstractDFALearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I> void addLearnerVariants(Alphabet<I> alphabet,
                                           int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/generic/it/GenericAAARLearnerMealyIT.java

@@ -23,14 +23,19 @@
 import de.learnlib.algorithm.aaar.TranslatingLearnerWrapper;
 import de.learnlib.algorithm.aaar.generic.GenericAAARLearnerMealy;
 import de.learnlib.oracle.MembershipOracle.MealyMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMealyLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MealyLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMealyLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MealyLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 import net.automatalib.word.Word;
 
 public class GenericAAARLearnerMealyIT extends AbstractMealyLearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I, O> void addLearnerVariants(Alphabet<I> alphabet,
                                              int targetSize,

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/generic/it/GenericAAARLearnerMooreIT.java

@@ -23,14 +23,19 @@
 import de.learnlib.algorithm.aaar.TranslatingLearnerWrapper;
 import de.learnlib.algorithm.aaar.generic.GenericAAARLearnerMoore;
 import de.learnlib.oracle.MembershipOracle.MooreMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMooreLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MooreLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMooreLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MooreLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.common.util.Pair;
 import net.automatalib.word.Word;
 
 public class GenericAAARLearnerMooreIT extends AbstractMooreLearnerIT {
 
+    @Override
+    protected boolean requiresQueriesDuringHypothesisTraversal() {
+        return true;
+    }
+
     @Override
     protected <I, O> void addLearnerVariants(Alphabet<I> alphabet,
                                              int targetSize,

algorithms/active/adt/src/test/java/de/learnlib/algorithm/adt/it/ADTIT.java

@@ -45,8 +45,8 @@
 import de.learnlib.statistic.Statistics;
 import de.learnlib.sul.SUL;
 import de.learnlib.testsupport.MQ2AQWrapper;
-import de.learnlib.testsupport.it.learner.AbstractMealyLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMealyLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList;
 import de.learnlib.util.Experiment.MealyExperiment;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.automaton.transducer.impl.CompactMealy;

algorithms/active/dhc/src/test/java/de/learnlib/algorithm/dhc/mealy/it/MealyDHCIT.java

@@ -19,8 +19,8 @@
 import de.learnlib.counterexample.GlobalSuffixFinder;
 import de.learnlib.counterexample.GlobalSuffixFinders;
 import de.learnlib.oracle.MembershipOracle.MealyMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMealyLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MealyLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMealyLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MealyLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.word.Word;
 

algorithms/active/kearns-vazirani/src/test/java/de/learnlib/algorithm/kv/dfa/KearnsVaziraniDFAIT.java

@@ -18,8 +18,8 @@
 import de.learnlib.acex.AbstractNamedAcexAnalyzer;
 import de.learnlib.acex.AcexAnalyzers;
 import de.learnlib.oracle.MembershipOracle.DFAMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractDFALearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.DFALearnerVariantList;
+import de.learnlib.testsupport.it.AbstractDFALearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.DFALearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import org.testng.annotations.Test;
 

algorithms/active/kearns-vazirani/src/test/java/de/learnlib/algorithm/kv/mealy/KearnsVaziraniMealyIT.java

@@ -18,8 +18,8 @@
 import de.learnlib.acex.AbstractNamedAcexAnalyzer;
 import de.learnlib.acex.AcexAnalyzers;
 import de.learnlib.oracle.MembershipOracle.MealyMembershipOracle;
-import de.learnlib.testsupport.it.learner.AbstractMealyLearnerIT;
-import de.learnlib.testsupport.it.learner.LearnerVariantList.MealyLearnerVariantList;
+import de.learnlib.testsupport.it.AbstractMealyLearnerIT;
+import de.learnlib.testsupport.it.variant.LearnerVariantList.MealyLearnerVariantList;
 import net.automatalib.alphabet.Alphabet;
 import org.testng.annotations.Test;
 

algorithms/active/lambda/src/main/java/de/learnlib/algorithm/lambda/ttt/AbstractTTTLambda.java

@@ -34,12 +34,13 @@
 import net.automatalib.automaton.concept.FiniteRepresentation;
 import net.automatalib.automaton.concept.SuffixOutput;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public abstract class AbstractTTTLambda<M extends SuffixOutput<I, D>, I, D>
         implements LearningAlgorithm<M, I, D>, SupportsGrowingAlphabet<I>, FiniteRepresentation {
 
     private final MembershipOracle<I, D> ceqs;
-    private final Alphabet<I> alphabet;
+    protected final Alphabet<I> alphabet;
     protected final SuffixTrie<I> strie;
     protected final PrefixTree<I, D> ptree;
 
@@ -53,7 +54,7 @@ protected AbstractTTTLambda(Alphabet<I> alphabet, MembershipOracle<I, D> ceqs) {
 
     protected abstract int maxSearchIndex(int ceLength);
 
-    protected abstract DTLeaf<I, D> getState(Word<I> prefix);
+    protected abstract @Nullable DTLeaf<I, D> getState(Word<I> prefix);
 
     protected abstract AbstractDecisionTree<I, D> dtree();
 
@@ -115,7 +116,7 @@ public void addAlphabetSymbol(I symbol) {
         }
     }
 
-    private void makeConsistent() {
+    protected void makeConsistent() {
         while (dtree().makeConsistent()) {
             // do nothing ...
         }
@@ -174,6 +175,7 @@ private void analyzeCounterexample(DefaultQuery<I, D> counterexample, Deque<Defa
         int mid = (upper + lower) / 2;
         Word<I> sprime = ce.suffix(ce.length() - (mid + 1));
         DTLeaf<I, D> qnext = getState(ua.word());
+        assert qnext != null;
         for (PTNode<I, D> uprime : qnext.getShortPrefixes()) {
             witnesses.push(new DefaultQuery<>(uprime.word(), sprime));
         }

algorithms/active/lambda/src/main/java/de/learnlib/algorithm/lambda/ttt/dfa/TTTLambdaDFA.java

@@ -24,6 +24,7 @@
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.automaton.fsa.DFA;
 import net.automatalib.word.Word;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class TTTLambdaDFA<I> extends AbstractTTTLambda<DFA<?, I>, I, Boolean> implements DFALearner<I> {
 
@@ -48,7 +49,7 @@ protected int maxSearchIndex(int ceLength) {
     }
 
     @Override
-    protected DTLeaf<I, Boolean> getState(Word<I> prefix) {
+    protected @Nullable DTLeaf<I, Boolean> getState(Word<I> prefix) {
         return hypothesis.getState(prefix);
     }
 

algorithms/active/lambda/src/main/java/de/learnlib/algorithm/lambda/ttt/mealy/DecisionTreeMealy.java

@@ -19,6 +19,7 @@
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 import de.learnlib.algorithm.lambda.ttt.dt.AbstractDecisionTree;
 import de.learnlib.algorithm.lambda.ttt.dt.Children;
@@ -31,7 +32,7 @@
 
 class DecisionTreeMealy<I, O> extends AbstractDecisionTree<I, Word<O>> {
 
-    private final Map<Word<I>, Word<O>> outputs;
+    private final Map<Word<I>, O> outputs;
 
     DecisionTreeMealy(MembershipOracle<I, Word<O>> mqOracle, Alphabet<I> sigma, STNode<I> stRoot) {
         super(sigma, mqOracle, stRoot);
@@ -45,11 +46,11 @@ protected Children<I, Word<O>> newChildren() {
 
     @Override
     protected Word<O> query(PTNode<I, Word<O>> prefix, STNode<I> suffix) {
-        return mqOracle.answerQuery(prefix.word(), suffix.word()).suffix(suffix.word().length());
+        return mqOracle.answerQuery(prefix.word(), suffix.word());
     }
 
-    Word<O> getOutput(DTLeaf<I, Word<O>> leaf, I a) {
-        return lookupOrQuery(leaf.getShortPrefixes().get(0).word(), Word.fromLetter(a));
+    O getOutput(DTLeaf<I, Word<O>> leaf, I a) {
+        return lookupOrQuery(leaf.getShortPrefixes().get(0).word(), a);
     }
 
     @Override
@@ -59,13 +60,13 @@ public boolean makeConsistent() {
                 continue;
             }
             for (I a : alphabet) {
-                Word<O> refOut = null;
+                O refOut = null;
                 List<PTNode<I, Word<O>>> sp = new LinkedList<>(n.getShortPrefixes());
                 for (PTNode<I, Word<O>> u : sp) {
-                    Word<O> out = lookupOrQuery(u.word(), Word.fromLetter(a));
+                    O out = lookupOrQuery(u.word(), a);
                     if (refOut == null) {
                         refOut = out;
-                    } else if (!refOut.equals(out)) {
+                    } else if (!Objects.equals(refOut, out)) {
                         n.split(sp.get(0), u, a);
                         return true;
                     }
@@ -75,11 +76,11 @@ public boolean makeConsistent() {
         return super.makeConsistent();
     }
 
-    private Word<O> lookupOrQuery(Word<I> prefix, Word<I> suffix) {
-        Word<I> lookup = prefix.concat(suffix);
-        Word<O> out = this.outputs.get(lookup);
+    private O lookupOrQuery(Word<I> prefix, I step) {
+        Word<I> lookup = prefix.append(step);
+        O out = this.outputs.get(lookup);
         if (out == null) {
-            out = mqOracle.answerQuery(prefix, suffix).suffix(1);
+            out = mqOracle.answerQuery(prefix, Word.fromLetter(step)).lastSymbol();
             this.outputs.put(lookup, out);
         }
         return out;