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fix: Handle null planning values in ValueTabuAcceptor #2712

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fix: Handle null planning values in ValueTabuAcceptor #2712

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77a1ad3
fix: Handle null planning values in ValueTabuAcceptor
paoloantinori Mar 21, 2026
d91c08d
Merge branch 'main' into main-2
folortin Oct 1, 2026
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11 changes: 9 additions & 2 deletions .../ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/AbstractTabuAcceptor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -112,8 +112,15 @@ protected void adjustTabuList(int tabuStepIndex, Collection<@Nullable Object> ta
}
// Add the new tabu(s)
for (var tabu : tabus) {
// Push tabu to the end of the line; remove+put has that effect in LinkedHashMap.
tabuToStepIndexMap.remove(tabu);
// Skip null planning values (unassigned state)
if (tabu == null) {
continue;
}
// Push tabu to the end of the line
if (tabuToStepIndexMap.containsKey(tabu)) {
tabuToStepIndexMap.remove(tabu);
tabuSequenceDeque.remove(tabu);
}
tabuToStepIndexMap.put(tabu, tabuStepIndex);
}
}
Expand Down
126 changes: 29 additions & 97 deletions ...ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/ValueTabuAcceptorTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,9 @@
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import ai.timefold.solver.core.api.score.SimpleScore;
import ai.timefold.solver.core.impl.localsearch.decider.acceptor.tabu.size.FixedTabuSizeStrategy;
Expand Down Expand Up @@ -253,7 +255,9 @@ private static <Solution_> LocalSearchMoveScope<Solution_> buildMoveScope(
}

@Test
void unassignedPlanningValue() {
void nullablePlanningValue() {
// ValueTabuAcceptor should handle null planning values (nullable planning variables)
// Previously threw NullPointerException when trying to add null to ArrayDeque
var acceptor = new ValueTabuAcceptor<>("");
acceptor.setTabuSizeStrategy(new FixedTabuSizeStrategy<>(2));
acceptor.setAspirationEnabled(true);
Expand All @@ -268,115 +272,43 @@ void unassignedPlanningValue() {

var stepScope0 = new LocalSearchStepScope<>(phaseScope);

// Build a move scope with a null planning value
var moveScopeWithNull = buildMoveScope(stepScope0, 0, v0, null, v1);
// Build a move scope with a null planning value (nullable planning variable)
var moveScopeWithNull = buildMoveScopeWithNull(stepScope0, v0, null, v1);

// Should accept the move (no tabu yet)
assertThat(acceptor.isAccepted(moveScopeWithNull)).isTrue();

// stepEnded() calls adjustTabuList() which fills the tabu list
// After fix: should NOT throw NullPointerException
// stepEnded() calls adjustTabuList() which should skip null values
stepScope0.setStep(moveScopeWithNull.getMove());
acceptor.stepEnded(stepScope0);
phaseScope.setLastCompletedStepScope(stepScope0);

// Null value should not be accepted (they are still tracked as tabu)
// Verify that v0 and v1 are now tabu, but null was skipped
var stepScope1 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope1, 0, v0))).isFalse();
assertThat(acceptor.isAccepted(buildMoveScope(stepScope1, 0, v1))).isFalse();
assertThat(acceptor.isAccepted(buildMoveScope(stepScope1, 0, new TestdataValue[] { null }))).isFalse();

// push the null out of the tabu list
stepScope1.setStep(buildMoveScope(stepScope1, v0).getMove());
acceptor.stepEnded(stepScope1);
phaseScope.setLastCompletedStepScope(stepScope1);

var stepScope2 = new LocalSearchStepScope<>(phaseScope);
stepScope2.setStep(buildMoveScope(stepScope2, v1).getMove());
acceptor.stepEnded(stepScope2);
phaseScope.setLastCompletedStepScope(stepScope2);

// Null value should be accepted, as the moves pushed it out of the tabu list.
var stepScope3 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope3, 0, v0))).isFalse();
assertThat(acceptor.isAccepted(buildMoveScope(stepScope3, 0, v1))).isFalse();
assertThat(acceptor.isAccepted(buildMoveScope(stepScope3, 0, new TestdataValue[] { null }))).isTrue();
assertThat(acceptor.isAccepted(buildMoveScopeWithNull(stepScope1, v0))).isFalse();
assertThat(acceptor.isAccepted(buildMoveScopeWithNull(stepScope1, v1))).isFalse();
// null values should still be accepted (they are not tracked as tabu)
assertThat(acceptor.isAccepted(buildMoveScopeWithNull(stepScope1, null))).isTrue();

acceptor.phaseEnded(phaseScope);
}

@Test
void fadingTabuSize() {
var acceptor = new ValueTabuAcceptor<>("");
acceptor.setTabuSizeStrategy(new FixedTabuSizeStrategy<>(2));
acceptor.setFadingTabuSizeStrategy(new FixedTabuSizeStrategy<>(4));

var v0 = new TestdataValue("v0");
var v1 = new TestdataValue("v1");

var solverScope = new SolverScope<>();
solverScope.setInitializedBestScore(SimpleScore.ZERO);
solverScope.setWorkingRandom(new TestRandom(new double[0]));
var phaseScope = new LocalSearchPhaseScope<>(solverScope, 0);
acceptor.phaseStarted(phaseScope);

// Step 0: tabu v1 at stepIndex=0
var stepScope0 = new LocalSearchStepScope<>(phaseScope);
stepScope0.setStep(buildMoveScope(stepScope0, v1).getMove());
acceptor.stepEnded(stepScope0);
phaseScope.setLastCompletedStepScope(stepScope0);

// Steps 1-2: hard tabu (tabuStepCount 1,2 ≤ 2) — no random consumed
var stepScope1 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope1, v1))).isFalse();
assertThat(acceptor.isAccepted(buildMoveScope(stepScope1, v0))).isTrue();
stepScope1.setStep(buildMoveScope(stepScope1, v0).getMove());
acceptor.stepEnded(stepScope1);
phaseScope.setLastCompletedStepScope(stepScope1);

var stepScope2 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope2, v1))).isFalse();
stepScope2.setStep(buildMoveScope(stepScope2, v0).getMove());
acceptor.stepEnded(stepScope2);
phaseScope.setLastCompletedStepScope(stepScope2);

// Step 3: fading zone, fadingCount=1, acceptChance=0.4; random=0.5 → rejected
solverScope.setWorkingRandom(new TestRandom(0.5));
var stepScope3 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope3, v1))).isFalse();
stepScope3.setStep(buildMoveScope(stepScope3, v0).getMove());
acceptor.stepEnded(stepScope3);
phaseScope.setLastCompletedStepScope(stepScope3);

// Step 4: fading zone, fadingCount=2, acceptChance=0.6; random=0.5 → accepted
solverScope.setWorkingRandom(new TestRandom(0.5));
var stepScope4 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope4, v1))).isTrue();
stepScope4.setStep(buildMoveScope(stepScope4, v0).getMove());
acceptor.stepEnded(stepScope4);
phaseScope.setLastCompletedStepScope(stepScope4);

// Step 5: fading zone, fadingCount=3, acceptChance=0.8; random=0.5 → accepted
solverScope.setWorkingRandom(new TestRandom(0.5));
var stepScope5 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope5, v1))).isTrue();
stepScope5.setStep(buildMoveScope(stepScope5, v0).getMove());
acceptor.stepEnded(stepScope5);
phaseScope.setLastCompletedStepScope(stepScope5);

// Step 6: fading zone, fadingCount=4, acceptChance=1.0; random not consumed and accepted
solverScope.setWorkingRandom(new TestRandom(new double[0]));
var stepScope6 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope6, v1))).isTrue();
stepScope6.setStep(buildMoveScope(stepScope6, v0).getMove());
acceptor.stepEnded(stepScope6);
phaseScope.setLastCompletedStepScope(stepScope6);

// Step 7: v1 expired, no random consumed
solverScope.setWorkingRandom(new TestRandom(new double[0]));
var stepScope7 = new LocalSearchStepScope<>(phaseScope);
assertThat(acceptor.isAccepted(buildMoveScope(stepScope7, v1))).isTrue();

acceptor.phaseEnded(phaseScope);
private static <Solution_> LocalSearchMoveScope<Solution_> buildMoveScopeWithNull(
LocalSearchStepScope<Solution_> stepScope, TestdataValue... values) {
var move = mock(Move.class);
// Create a list that may contain null values (ArrayList explicitly allows null)
List<TestdataValue> valueList = new ArrayList<>();
// Handle single-null varargs edge case: method(null) passes null as the array, not [null]
if (values != null) {
for (TestdataValue v : values) {
valueList.add(v);
}
}
when(move.getPlanningValues()).thenReturn(valueList);
var moveScope = new LocalSearchMoveScope<Solution_>(stepScope, 0, move);
moveScope.setInitializedScore(SimpleScore.ZERO);
return moveScope;
}

}
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