perf(parser): add collection capacity hints to known-size loops - #1791
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Oh, the dedupe can shrink the input, so reserving before it over-allocates. I'll shift reserveCapacity after the dedupe in both tmpfsMounts and mounts. |
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jglogan
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@hluaguo Merged, thank you for the optimization! |
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…e#1791) - For result sets with known sizes, it's more efficient to supply the size as a capacity hint.
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Type of Change
Motivation and Context
Methods in Parser.swift and Utility.swift build arrays and dictionaries in loops where the final size is known from the input parameter count, but none pre-allocate storage. Without a capacity hint, Array.append grows the backing store exponentially (2x), causing O(log n) reallocation+copies per call. These methods execute on every
container run/createcommand, so the savings compound at scale.Testing
Added 7 new tests with large inputs (50-100 entries) that exercise the capacity-allocated code paths. All 183 existing tests pass with zero regressions.