feat: make Compressor::train 2x faster with bitmap index #16
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The slowest part of Compressor::train is the double-nested loops over codes. Now compress_count when it records code pairs will also populate a bitmap index, where `pairs_index[code1].set(code2)` will indicate that code2 followed code1 in compressed output. In the `optimize` loop, we can eliminate tight loop iterations by accessing `pairse_index[code1].second_codes()` which yields the value code2 values. This results in a speedup from ~1ms -> 500micros.
a10y
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Aug 20, 2024
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| pub fn reset(&mut self) { | ||
| for idx in 0..COUNTS1_SIZE { | ||
| self.counts1[idx] = 0; | ||
| } | ||
| for idx in 0..COUNTS2_SIZE { | ||
| self.counts2[idx] = 0; |
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this was slower than just building a new Counter b/c of the vec![0] change made in the previous PR
i don't want to lose my 30s CI checks
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## 🤖 New release * `fsst-rs`: 0.2.0 -> 0.2.1 <details><summary><i><b>Changelog</b></i></summary><p> <blockquote> ## [0.2.1](v0.2.0...v0.2.1) - 2024-08-20 ### Added - make Compressor::train 2x faster with bitmap index ([#16](#16)) </blockquote> </p></details> --- This PR was generated with [release-plz](https://github.com/MarcoIeni/release-plz/). Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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| if self.block == 0 { | ||
| return None; | ||
| } |
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Shouldn't it be possible to skip this check?
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The slowest part of Compressor::train is the double-nested loops over codes.
Now compress_count when it records code pairs will also populate a bitmap index, where
pairs_index[code1].set(code2)will indicate that code2 followed code1 in compressed output.In the
optimizeloop, we can eliminate tight loop iterations by accessingpairse_index[code1].second_codes()which yields the value code2 values.This results in a speedup from ~1ms -> 500micros for the training benchmark. We're sub-millisecond!
This also makes Miri somewhat palatable to run for all but
test_large, so I've re-enabled it for CI (currently it runs in 2.5 minutes. Far cry from the < 30s build+test step but I guess it's for a good cause)