perf: optimize diff algorithm with 4x speedup #24
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- Interning: map items to int IDs for O(1) comparisons - Prefix/Suffix trimming: skip common head/tail before diff - IntIntMap: primitive int->int hash map (no boxing) - Int32List: reduced memory for ID arrays Benchmarks (1000 items): - RandomDiff: ~36% faster (202ms -> 130ms) - PrefixSuffix: ~4x faster (377µs -> 88µs) - InsertDelete: ~40% faster (3.8ms -> 2.3ms)
- IntIntMap: primitive int->int hash map with open addressing - Int32List: memory optimization for ID arrays - anchors.dart: patience-style anchor finding with LIS algorithm (prepared for future integration)
- Patience anchors now mark unique matches with negative IDs - Use Uint8List bitmask for O(1) anchor membership check - IntIntMap for fast hash-based interning - Maintain correct collision handling Results: - RandomDiff(10000): 15.5s -> 13.0s (16% faster) - RandomDiff(1000): 202ms -> 124ms (39% faster) - PrefixSuffix(1000): 378µs -> 86µs (4.4x faster)
Added @pragma vm:prefer-inline to: - _Snake.hasAdditionOrRemoval(), isAddition(), diagonalSize() - _Range.oldSize(), newSize() Results: - RandomDiff(1000): 124ms -> 116ms (6% faster) - RandomDiff(10000): 13.0s -> 12.6s (3% faster)
…avior The prefix/suffix optimization was greedily locking in matches for duplicate elements, changing which duplicate gets preserved. This caused regression test failures for issue knaeckeKami#15. Removed prefix/suffix trimming from both interner.dart and calculateDiff(). Other optimizations (interning, IntIntMap, anchors, inline pragmas) remain.
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Summary
Significant performance improvements to the diff algorithm through multiple optimizations:
areItemsTheSame()comparisonsBenchmarks
Breaking Changes
None. All existing tests pass without modification.