perf: further improve performance of ElementAwareArrayList#2373
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Pull request overview
This PR continues performance-focused work by optimizing ElementAwareArrayList internals (gap tracking/compaction and backing-array retention), refining tabu acceptor behavior (including deterministic fading-taboo decisions), and simplifying Bavet leaf indexing by removing the linked-list backend.
Changes:
- Reworked
ElementAwareArrayListto avoid fail-fast iteration/modCount overhead, addcompact()+firstGapPositionfast paths, and free large backing arrays when the list becomes empty. - Updated tabu acceptors to use a new fading-taboo decision path with deterministic random consumption behavior; tightened configuration validation and tabu size constraints.
- Removed
LinkedListLeafIndexerand switched indexer construction/tests toRandomAccessLeafIndexer.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| core/src/main/java/ai/timefold/solver/core/impl/util/ElementAwareArrayList.java | Optimizes gap handling/compaction, iterator behavior, and backing array retention/freeing. |
| core/src/test/java/ai/timefold/solver/core/impl/util/ElementAwareArrayListTest.java | Adds tests for compaction/first-gap behavior and backing-array free-path; adds randomized stress test. |
| core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/AbstractTabuAcceptor.java | Refactors fading-taboo acceptance into a decision helper that can avoid consuming random in certain outcomes. |
| core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/size/FixedTabuSizeStrategy.java | Enforces tabu size must be at least 1 and improves exception message. |
| core/src/test/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/size/FixedTabuSizeStrategyTest.java | Adds test coverage for invalid tabu sizes (0 and negative). |
| core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/AcceptorFactory.java | Improves error messages, validates tabu acceptor configs, and removes duplicated configuration code. |
| core/src/test/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/AcceptorFactoryTest.java | Verifies factory rejects tabu acceptors without configured sizes. |
| core/src/test/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/ValueTabuAcceptorTest.java | Adds fading-taboo behavior test using deterministic TestRandom. |
| core/src/test/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/EntityTabuAcceptorTest.java | Adds fading-taboo behavior test using deterministic TestRandom. |
| core/src/test/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/MoveTabuAcceptorTest.java | Introduces move-taboo tests, including fading-taboo and aspiration scenarios. |
| core/src/main/java/ai/timefold/solver/core/impl/bavet/common/index/LinkedListLeafIndexer.java | Removed linked-list leaf backend implementation. |
| core/src/main/java/ai/timefold/solver/core/impl/bavet/common/index/LeafIndexer.java | Updates sealed permits to remove the deleted linked-list backend. |
| core/src/main/java/ai/timefold/solver/core/impl/bavet/common/index/IndexerFactory.java | Switches indexer backend creation to always use RandomAccessLeafIndexer. |
| core/src/test/java/ai/timefold/solver/core/impl/bavet/common/index/FusedEqualIndexTest.java | Updates fused equal index test to use RandomAccessLeafIndexer. |
zepfred
reviewed
Jun 15, 2026
zepfred
reviewed
Jun 15, 2026
zepfred
reviewed
Jun 15, 2026
zepfred
reviewed
Jun 15, 2026
zepfred
reviewed
Jun 15, 2026
zepfred
reviewed
Jun 15, 2026
zepfred
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Jun 15, 2026
zepfred
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Looks good to me. I have a few minor comments and some questions.
This reverts commit 9ba4ff6.
|
zepfred
approved these changes
Jun 19, 2026
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The goal here is to minimize the overhead of add/remove methods, as they showed up the highest in profiling in comparison to the original ElementAwareLinkedList.