Add a string-specific search algorithm #715
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This adds a Boyer-Moore substring search algorithm, and updates the `firstRange(of:)` and `ranges(of:)` methods to use that when both pieces of the search are strings/substrings. Still need to look at availability and switch the "replacing" methods to use this new search algorithm.
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For large strings, a recursive search can run out of stack space. This eliminates the issue by looping within the `nextRange` function.
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Benchmark metrics of the improvements:
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Updated the algorithm to skip calculating the bad-character offset table when the pattern is very short, since the benefit of skipping is reduced. Updated benchmarks:
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Catfish-Man
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Jun 8, 2024
| @@ -135,7 +135,7 @@ extension Collection where Element: Equatable { | |||
| ) -> RangesCollection<ZSearcher<Self>> where C.Element == Element { | |||
| _ranges(of: ZSearcher(pattern: Array(other), by: ==)) | |||
| } | |||
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| // FIXME: Return `some Collection<Range<Index>>` for SE-0346 | |||
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I was about to comment about the extra Array allocation then saw there was already a fixme about it
| with: replacement, | ||
| maxReplacements: maxReplacements) | ||
| switch (self, other, replacement) { | ||
| case (let str as String, let other as String, let repl as String): |
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This is a bit painful but I don't see a better way to do it
natecook1000
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Jun 10, 2024
* Add a string-specific search algorithm This adds a Boyer-Moore substring search algorithm, and updates the `firstRange(of:)` and `ranges(of:)` methods to use that when both pieces of the search are strings/substrings. * Substring search: iterative rather than recursive For large strings, a recursive search can run out of stack space. This eliminates the issue by looping within the `nextRange` function. * Dispatch string splitting to new searcher * Remove generic on SubstringSearcher * Remove unnecessary inlining annotations * Update string algorithms tests * Verify string/substring dispatch in algorithms * Add tests for string.replacing maxReplacements * Add fallback to naive search for small patterns * Improve some comments/formatting in the string search
natecook1000
added a commit
that referenced
this pull request
Jun 10, 2024
* Add a string-specific search algorithm This adds a Boyer-Moore substring search algorithm, and updates the `firstRange(of:)` and `ranges(of:)` methods to use that when both pieces of the search are strings/substrings. * Substring search: iterative rather than recursive For large strings, a recursive search can run out of stack space. This eliminates the issue by looping within the `nextRange` function. * Dispatch string splitting to new searcher * Remove generic on SubstringSearcher * Remove unnecessary inlining annotations * Update string algorithms tests * Verify string/substring dispatch in algorithms * Add tests for string.replacing maxReplacements * Add fallback to naive search for small patterns * Improve some comments/formatting in the string search
This was referenced Jun 10, 2024
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This adds a Boyer-Moore substring search algorithm, and updates the
firstRange(of:),ranges(of:),split(...), andreplacingmethods to use that when both pieces of the search are strings/substrings.