perf: avoid boxing in externalized list var cases#2420
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Pull request overview
This PR optimizes list-variable index lookups by avoiding boxing when index shadow variables are externalized, changing index access from nullable Integer to primitive int with -1 as the “unassigned” sentinel.
Changes:
- Changed
ListVariableStateSupply#getIndex(...)from@Nullable Integertoint(using-1for unassigned) and updated helpers accordingly. - Updated delegating/index lookup plumbing to use
ToIntFunctionto avoid boxing. - Adjusted relevant test wiring to the new functional type.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| core/src/test/java/ai/timefold/solver/core/impl/heuristic/selector/move/generic/list/kopt/KOptUtilsTest.java | Updates test helper to use the new DelegatingListVariableStateSupply signature without boxing. |
| core/src/main/java/ai/timefold/solver/core/impl/heuristic/selector/move/generic/list/kopt/DelegatingListVariableStateSupply.java | Switches index function to ToIntFunction to avoid boxing in K-opt utilities. |
| core/src/main/java/ai/timefold/solver/core/impl/domain/variable/ListVariableStateSupply.java | Changes index API to primitive int and documents -1 as the unassigned sentinel. |
| core/src/main/java/ai/timefold/solver/core/impl/domain/variable/ListVariableState.java | Propagates the -1 sentinel internally and adapts null-handling for externalized index storage. |
| core/src/main/java/ai/timefold/solver/core/impl/domain/variable/ExternalizedListVariableStateSupply.java | Updates implementation to match the new primitive getIndex contract. |
Christopher-Chianelli
approved these changes
Jun 25, 2026
Christopher-Chianelli
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Christopher-Chianelli
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Did we not check if index == null anywhere in this code base when accessing a listVariableState? Changes LGTM, but it seems a bit small.
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6-7 % in CVRP profiling.