feat: adaptive late acceptance

Author: zepfred

benchmark/src/main/resources/benchmark.xsd

@@ -3146,7 +3146,7 @@
       <xs:enumeration value="DIVERSIFIED_LATE_ACCEPTANCE"/>
 
 
-      <xs:enumeration value="ITERATED_LOCAL_SEARCH"/>
+      <xs:enumeration value="ADAPTIVE_LATE_ACCEPTANCE"/>
 
 
       <xs:enumeration value="GREAT_DELUGE"/>

core/src/main/java/ai/timefold/solver/core/config/localsearch/decider/acceptor/AcceptorType.java

@@ -12,7 +12,7 @@ public enum AcceptorType {
     SIMULATED_ANNEALING,
     LATE_ACCEPTANCE,
     DIVERSIFIED_LATE_ACCEPTANCE,
-    ITERATED_LOCAL_SEARCH,
+    ADAPTIVE_LATE_ACCEPTANCE,
     GREAT_DELUGE,
     STEP_COUNTING_HILL_CLIMBING
 }

core/src/main/java/ai/timefold/solver/core/impl/localsearch/DefaultLocalSearchPhaseFactory.java

@@ -70,9 +70,8 @@ phaseTermination, buildDecider(phaseConfigPolicy, phaseTermination))
     private LocalSearchDecider<Solution_> buildDecider(HeuristicConfigPolicy<Solution_> configPolicy,
             PhaseTermination<Solution_> termination) {
         var moveSelector = buildMoveSelector(configPolicy);
-        var perturbationMoveSelector = buildPerturbationMoveSelector(configPolicy);
         var acceptor = buildAcceptor(configPolicy);
-        RestartStrategy<Solution_> restartStrategy = new AcceptorRestartStrategy<>(perturbationMoveSelector, acceptor);
+        RestartStrategy<Solution_> restartStrategy = new AcceptorRestartStrategy<>(acceptor);
         var forager = buildForager(configPolicy);
         if (moveSelector.isNeverEnding() && !forager.supportsNeverEndingMoveSelector()) {
             throw new IllegalStateException("The moveSelector (" + moveSelector

core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/LocalSearchDecider.java

@@ -193,9 +193,14 @@ public void solvingEnded(SolverScope<Solution_> solverScope) {
         forager.solvingEnded(solverScope);
     }
 
-    public void restoreCurrentBestSolution(LocalSearchPhaseScope<Solution_> phaseScope) {
-        phaseScope.getSolverScope().setWorkingSolutionFromBestSolution();
-        moveSelectorPhaseStarted(phaseScope);
+    public void restoreCurrentBestSolution(LocalSearchStepScope<Solution_> stepScope) {
+        stepScope.getPhaseScope().getSolverScope().setWorkingSolutionFromBestSolution();
+        stepScope.setScore(stepScope.getPhaseScope().getBestScore());
+        // Changing the working solution requires reinitializing the move selector.
+        // The acceptor should not be restarted, as this may lead to an inconsistent state,
+        // such as changing the scores of all late elements in LA and DLAS.
+        // 1 - The move selector will reset all cached lists using old solution entity references
+        moveSelector.phaseStarted(stepScope.getPhaseScope());
     }
 
     public void solvingError(SolverScope<Solution_> solverScope, Exception exception) {

core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/AcceptorFactory.java

@@ -13,7 +13,7 @@
 import ai.timefold.solver.core.impl.heuristic.HeuristicConfigPolicy;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.greatdeluge.GreatDelugeAcceptor;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.hillclimbing.HillClimbingAcceptor;
-import ai.timefold.solver.core.impl.localsearch.decider.acceptor.iteratedlocalsearch.IteratedLocalSearchAcceptor;
+import ai.timefold.solver.core.impl.localsearch.decider.acceptor.iteratedlocalsearch.AdaptiveLateAcceptanceAcceptor;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.lateacceptance.DiversifiedLateAcceptanceAcceptor;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.lateacceptance.LateAcceptanceAcceptor;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.simulatedannealing.SimulatedAnnealingAcceptor;
@@ -244,11 +244,11 @@ private Optional<MoveTabuAcceptor<Solution_>> buildMoveTabuAcceptor(HeuristicCon
         return Optional.empty();
     }
 
-    private Optional<IteratedLocalSearchAcceptor<Solution_>>
+    private Optional<AdaptiveLateAcceptanceAcceptor<Solution_>>
             buildIteratedLocalSearchAcceptor() {
-        if (acceptorTypeListsContainsAcceptorType(AcceptorType.ITERATED_LOCAL_SEARCH)) {
+        if (acceptorTypeListsContainsAcceptorType(AcceptorType.ADAPTIVE_LATE_ACCEPTANCE)) {
             StuckCriterion<Solution_> strategy = new UnimprovedMoveCountStuckCriterion<>();
-            var acceptor = new IteratedLocalSearchAcceptor<>(3, strategy);
+            var acceptor = new AdaptiveLateAcceptanceAcceptor<>(strategy);
             return Optional.of(acceptor);
         }
         return Optional.empty();

…lsearch/IteratedLocalSearchAcceptor.java …arch/AdaptiveLateAcceptanceAcceptor.javacore/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/iteratedlocalsearch/IteratedLocalSearchAcceptor.java renamed to core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/iteratedlocalsearch/AdaptiveLateAcceptanceAcceptor.java core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/iteratedlocalsearch/IteratedLocalSearchAcceptor.java renamed to core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/iteratedlocalsearch/AdaptiveLateAcceptanceAcceptor.java

@@ -1,7 +1,6 @@
 package ai.timefold.solver.core.impl.localsearch.decider.acceptor.iteratedlocalsearch;
 
 import ai.timefold.solver.core.api.score.Score;
-import ai.timefold.solver.core.impl.heuristic.selector.move.MoveSelector;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.RestartableAcceptor;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.lateacceptance.LateAcceptanceAcceptor;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.stuckcriterion.StuckCriterion;
@@ -10,35 +9,27 @@
 import ai.timefold.solver.core.impl.localsearch.scope.LocalSearchPhaseScope;
 import ai.timefold.solver.core.impl.localsearch.scope.LocalSearchStepScope;
 
-public class IteratedLocalSearchAcceptor<Solution_> extends RestartableAcceptor<Solution_> {
+public class AdaptiveLateAcceptanceAcceptor<Solution_> extends RestartableAcceptor<Solution_> {
 
     private static final int[] LATE_ELEMENTS_SIZE =
-            new int[] { 12_500, 25_000, 25_000, 50_000, 50_000 };
+            new int[] { 2_500, 5_000, 12_500, 25_000, 25_000 };
     private static final int[] LATE_ELEMENTS_MAX_REJECTIONS =
-            new int[] { 12_500, 25_000, 50_000, 50_000, 75_000 };
+            new int[] { 5_000, 5_000, 12_500, 25_000, 50_000 };
     private final LateAcceptanceAcceptor<Solution_> lateAcceptanceAcceptor;
-    private MoveSelector<Solution_> perturbationMoveSelector;
-    private final int maxPerturbationCount;
     private int lateIndex;
-    private int perturbationCount;
-    private Score<?> currentBestScore;
+    private Score<?> initialScore;
 
-    public IteratedLocalSearchAcceptor(int maxPerturbationCount, StuckCriterion<Solution_> stuckCriterion) {
+    public AdaptiveLateAcceptanceAcceptor(StuckCriterion<Solution_> stuckCriterion) {
         super(true, stuckCriterion);
-        this.maxPerturbationCount = maxPerturbationCount;
         this.lateAcceptanceAcceptor = new LateAcceptanceAcceptor<>(false, false, null);
     }
 
-    public void setPerturbationMoveSelector(MoveSelector<Solution_> perturbationMoveSelector) {
-        this.perturbationMoveSelector = perturbationMoveSelector;
-    }
-
     @Override
     public void phaseStarted(LocalSearchPhaseScope<Solution_> phaseScope) {
         super.phaseStarted(phaseScope);
-        perturbationCount = 1;
+        initialScore = phaseScope.getBestScore();
         lateIndex = 0;
-        lateAcceptanceAcceptor.setLateAcceptanceSize(LATE_ELEMENTS_SIZE[perturbationCount]);
+        lateAcceptanceAcceptor.setLateAcceptanceSize(LATE_ELEMENTS_SIZE[lateIndex]);
         lateAcceptanceAcceptor.phaseStarted(phaseScope);
         stuckCriterion.reset(phaseScope);
         if (stuckCriterion instanceof UnimprovedMoveCountStuckCriterion<Solution_> stepCountStuckCriterion) {
@@ -50,23 +41,18 @@ public void phaseStarted(LocalSearchPhaseScope<Solution_> phaseScope) {
     public void phaseEnded(LocalSearchPhaseScope<Solution_> phaseScope) {
         super.phaseEnded(phaseScope);
         this.lateAcceptanceAcceptor.phaseEnded(phaseScope);
-
     }
 
     @Override
     public void stepStarted(LocalSearchStepScope<Solution_> stepScope) {
         super.stepStarted(stepScope);
         lateAcceptanceAcceptor.stepStarted(stepScope);
-        currentBestScore = stepScope.getPhaseScope().getBestScore();
     }
 
     @Override
     public void stepEnded(LocalSearchStepScope<Solution_> stepScope) {
         super.stepEnded(stepScope);
         lateAcceptanceAcceptor.stepEnded(stepScope);
-        if (((Score) stepScope.getScore()).compareTo(currentBestScore) > 0) {
-            perturbationCount = 1;
-        }
     }
 
     @Override
@@ -78,34 +64,19 @@ public boolean rejectRestartEvent() {
     @Override
     public void restart(LocalSearchStepScope<Solution_> stepScope) {
         lateIndex = (lateIndex + 1) % LATE_ELEMENTS_SIZE.length;
-        var lastCompletedStepScore = stepScope.getPhaseScope().getLastCompletedStepScope().getScore();
         var phaseScope = stepScope.getPhaseScope();
         var decider = phaseScope.getDecider();
         // Restore the current best solution
-        decider.restoreCurrentBestSolution(phaseScope);
-        // Apply the perturbation with perturbation move selector
-        for (int i = 0; i < perturbationCount; i++) {
-            perturbationMoveSelector.phaseStarted(phaseScope);
-            var iterator = perturbationMoveSelector.iterator();
-            if (iterator.hasNext()) {
-                decider.doMoveOnly(phaseScope, iterator.next());
-            }
-        }
-        // Reset cached entity list
-        decider.moveSelectorPhaseStarted(phaseScope);
+        decider.restoreCurrentBestSolution(stepScope);
         logger.info(
-                "Restart event triggered, step count ({}), perturbation count ({}), late elements size ({}), max rejections ({}), best score ({}), last completed score ({}), new perturbation score ({}),",
-                stepScope.getStepIndex(), perturbationCount, LATE_ELEMENTS_SIZE[lateIndex],
-                LATE_ELEMENTS_MAX_REJECTIONS[lateIndex], stepScope.getPhaseScope().getBestScore(),
-                lastCompletedStepScore,
-                stepScope.getPhaseScope().getLastCompletedStepScope().getScore());
-        lateAcceptanceAcceptor.resetLateElementsScore(LATE_ELEMENTS_SIZE[lateIndex],
-                (Score) stepScope.getPhaseScope().getLastCompletedStepScope().getScore());
+                "Restart event triggered, step count ({}), late elements size ({}), max rejections ({}), best score ({}), new perturbation score ({}),",
+                stepScope.getStepIndex(), LATE_ELEMENTS_SIZE[lateIndex], LATE_ELEMENTS_MAX_REJECTIONS[lateIndex],
+                stepScope.getPhaseScope().getBestScore(), initialScore);
+        lateAcceptanceAcceptor.resetLateElementsScore(LATE_ELEMENTS_SIZE[lateIndex], (Score) initialScore);
         if (stuckCriterion instanceof UnimprovedMoveCountStuckCriterion<Solution_> stepCountStuckCriterion) {
             stepCountStuckCriterion.setMaxRejected(LATE_ELEMENTS_MAX_REJECTIONS[lateIndex]);
         }
         stuckCriterion.reset(stepScope.getPhaseScope());
-        perturbationCount = (perturbationCount % maxPerturbationCount) + 1;
     }
 
     @Override

core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/restart/AcceptorRestartStrategy.java

@@ -1,21 +1,17 @@
 package ai.timefold.solver.core.impl.localsearch.decider.restart;
 
-import ai.timefold.solver.core.impl.heuristic.selector.move.MoveSelector;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.Acceptor;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.RestartableAcceptor;
-import ai.timefold.solver.core.impl.localsearch.decider.acceptor.iteratedlocalsearch.IteratedLocalSearchAcceptor;
 import ai.timefold.solver.core.impl.localsearch.scope.LocalSearchStepScope;
 import ai.timefold.solver.core.impl.phase.scope.AbstractPhaseScope;
 import ai.timefold.solver.core.impl.phase.scope.AbstractStepScope;
 import ai.timefold.solver.core.impl.solver.scope.SolverScope;
 
 public final class AcceptorRestartStrategy<Solution_> implements RestartStrategy<Solution_> {
 
-    private final MoveSelector<Solution_> perturbationMoveSelector;
     private final Acceptor<Solution_> acceptor;
 
-    public AcceptorRestartStrategy(MoveSelector<Solution_> perturbationMoveSelector, Acceptor<Solution_> acceptor) {
-        this.perturbationMoveSelector = perturbationMoveSelector;
+    public AcceptorRestartStrategy(Acceptor<Solution_> acceptor) {
         this.acceptor = acceptor;
     }
 
@@ -30,34 +26,31 @@ public void applyRestart(AbstractStepScope<Solution_> stepScope) {
 
     @Override
     public void stepStarted(AbstractStepScope<Solution_> stepScope) {
-        perturbationMoveSelector.stepStarted(stepScope);
+        // Do nothing
     }
 
     @Override
     public void stepEnded(AbstractStepScope<Solution_> stepScope) {
-        perturbationMoveSelector.stepEnded(stepScope);
+        // Do nothing
     }
 
     @Override
     public void phaseStarted(AbstractPhaseScope<Solution_> phaseScope) {
-        perturbationMoveSelector.phaseStarted(phaseScope);
+        // Do nothing
     }
 
     @Override
     public void phaseEnded(AbstractPhaseScope<Solution_> phaseScope) {
-        perturbationMoveSelector.phaseEnded(phaseScope);
+        // Do nothing
     }
 
     @Override
     public void solvingStarted(SolverScope<Solution_> solverScope) {
-        perturbationMoveSelector.solvingStarted(solverScope);
-        if (acceptor instanceof IteratedLocalSearchAcceptor<Solution_> iteratedLocalSearchAcceptor) {
-            iteratedLocalSearchAcceptor.setPerturbationMoveSelector(perturbationMoveSelector);
-        }
+        // Do nothing
     }
 
     @Override
     public void solvingEnded(SolverScope<Solution_> solverScope) {
-        perturbationMoveSelector.solvingEnded(solverScope);
+        // Do nothing
     }
 }

core/src/main/resources/solver.xsd

@@ -1923,7 +1923,7 @@
 
       <xs:enumeration value="DIVERSIFIED_LATE_ACCEPTANCE"/>
 
-      <xs:enumeration value="ITERATED_LOCAL_SEARCH"/>
+      <xs:enumeration value="ADAPTIVE_LATE_ACCEPTANCE"/>
 
       <xs:enumeration value="GREAT_DELUGE"/>
 

core/src/test/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/lateacceptance/LateAcceptanceAcceptorTest.java

@@ -7,7 +7,6 @@
 import static org.mockito.Mockito.when;
 
 import ai.timefold.solver.core.api.score.buildin.simple.SimpleScore;
-import ai.timefold.solver.core.impl.heuristic.selector.move.MoveSelector;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.AbstractAcceptorTest;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.stuckcriterion.StuckCriterion;
 import ai.timefold.solver.core.impl.localsearch.decider.restart.AcceptorRestartStrategy;
@@ -390,9 +389,8 @@ void restart() {
     @Test
     void ensureDiversity() {
         var stuckCriterion = mock(StuckCriterion.class);
-        var moveSelector = mock(MoveSelector.class);
         var acceptor = new LateAcceptanceAcceptor<>(true, stuckCriterion);
-        var restartStrategy = new AcceptorRestartStrategy(moveSelector, acceptor);
+        var restartStrategy = new AcceptorRestartStrategy(acceptor);
         acceptor.setLateAcceptanceSize(5);
         var solverScope = new SolverScope<>();
         var phaseScope = new LocalSearchPhaseScope<>(solverScope, 0);
@@ -420,9 +418,8 @@ void ensureDiversity() {
     @Test
     void reconfigureAfterImprovement() {
         var stuckCriterion = mock(StuckCriterion.class);
-        var moveSelector = mock(MoveSelector.class);
         var acceptor = new LateAcceptanceAcceptor<>(true, stuckCriterion);
-        var restartStrategy = new AcceptorRestartStrategy(moveSelector, acceptor);
+        var restartStrategy = new AcceptorRestartStrategy(acceptor);
         acceptor.setLateAcceptanceSize(5);
         var solverScope = new SolverScope<>();
         var phaseScope = new LocalSearchPhaseScope<>(solverScope, 0);

core/src/test/java/ai/timefold/solver/core/impl/localsearch/decider/restart/AcceptorRestartStrategyTest.java

@@ -6,7 +6,6 @@
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
-import ai.timefold.solver.core.impl.heuristic.selector.move.MoveSelector;
 import ai.timefold.solver.core.impl.localsearch.decider.acceptor.lateacceptance.LateAcceptanceAcceptor;
 import ai.timefold.solver.core.impl.localsearch.scope.LocalSearchPhaseScope;
 import ai.timefold.solver.core.impl.localsearch.scope.LocalSearchStepScope;
@@ -18,12 +17,11 @@ class AcceptorRestartStrategyTest {
     @Test
     void restart() {
         // Restore the best solution
-        var moveSelector = mock(MoveSelector.class);
         var phaseScope = mock(LocalSearchPhaseScope.class);
         var stepScope = mock(LocalSearchStepScope.class);
         when(stepScope.getPhaseScope()).thenReturn(phaseScope);
         var acceptor = mock(LateAcceptanceAcceptor.class);
-        var strategy = new AcceptorRestartStrategy<>(moveSelector, acceptor);
+        var strategy = new AcceptorRestartStrategy<>(acceptor);
 
         // Call acceptor restart logic
         strategy.applyRestart(stepScope);