jhorstmann opened a new pull request, #4453:
URL: https://github.com/apache/arrow-rs/pull/4453
# Which issue does this PR close?
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Closes #.
# Rationale for this change
I noticed an unexpected hotspot when profiling parquet benchmarks for
dictionary encoded arrays. The range checks that verify keys are in bounds take
a relatively large amount of time. There was already a comment suggesting to
use simd instructions, and in my opinion the compiler should have been able to
auto-vectorize the existing code, but it took some experimentation to get the
compiler generate more efficient code.
### Benchmark results compared to master branch on my laptop
(using rust 1.70, there was no change in generated code in earlier versions)
```
$ RUSTFLAGS="-Ctarget-cpu=skylake" cargo bench --features
arrow,test_common,experimental --bench arrow_reader -- --baseline master
StringDictionary
arrow_array_reader/StringDictionary/dictionary encoded, mandatory, no NULLs
time: [15.197 µs 15.334 µs 15.520 µs]
change: [-33.272% -32.922% -32.535%] (p = 0.00 <
0.05)
Performance has improved.
arrow_array_reader/StringDictionary/dictionary encoded, optional, no NULLs
time: [16.166 µs 16.213 µs 16.268 µs]
change: [-31.508% -31.347% -31.181%] (p = 0.00 <
0.05)
Performance has improved.
arrow_array_reader/StringDictionary/dictionary encoded, optional, half NULLs
time: [36.581 µs 36.735 µs 36.932 µs]
change: [-11.060% -10.605% -10.166%] (p = 0.00 <
0.05)
Performance has improved.
```
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# What changes are included in this PR?
basically a one-line change
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# Are there any user-facing changes?
no
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