andygrove opened a new pull request, #4916:
URL: https://github.com/apache/datafusion-comet/pull/4916
> This PR was created by an LLM as a draft PR. I will mark it as ready for
review after human review.
## Which issue does this PR close?
N/A — autonomous exploratory PR.
## Rationale for this change
Replaced six redundant scans plus two str::parse calls with a single
validating byte pass and direct i128 digit accumulation, gated the seven
inf/nan string comparisons behind a first-byte check, and swapped 10_i128.pow
for a const power-of-ten table.
## What changes are included in this PR?
Replaced six redundant scans plus two str::parse calls with a single
validating byte pass and direct i128 digit accumulation, gated the seven
inf/nan string comparisons behind a first-byte check, and swapped 10_i128.pow
for a const power-of-ten table.
## How are these changes tested?
Correctness: unit tests + seeded differential fuzz (bit-identical Arrow
output vs `main`).
Benchmark (criterion):
- decimal_38_10: 41.516% faster (base 265533ns -> cand 155293ns)
- decimal_18_2: 36.846% faster (base 302661ns -> cand 191142ns)
- decimal_38_10: 40.979% faster (base 266661ns -> cand 157386ns)
- decimal_18_2: 36.564% faster (base 305466ns -> cand 193776ns)
- decimal_38_10: 40.66% faster (base 264940ns -> cand 157214ns)
- decimal_18_2: 36.607% faster (base 303296ns -> cand 192269ns)
Full criterion output:
```text
cast_string_to_decimal/legacy/decimal_38_10
time: [156.99 µs 157.35 µs 157.96 µs]
change: [−41.202% −40.979% −40.792%] (p = 0.00 <
0.05)
Performance has improved.
Found 10 outliers among 100 measurements (10.00%)
2 (2.00%) low severe
1 (1.00%) low mild
1 (1.00%) high mild
6 (6.00%) high severe
cast_string_to_decimal/legacy/decimal_18_2
time: [193.54 µs 193.64 µs 193.77 µs]
change: [−36.658% −36.564% −36.469%] (p = 0.00 <
0.05)
Performance has improved.
Found 10 outliers among 100 measurements (10.00%)
3 (3.00%) low severe
1 (1.00%) low mild
2 (2.00%) high mild
4 (4.00%) high severe
cast_string_to_decimal/ansi/decimal_38_10
time: [155.19 µs 155.26 µs 155.35 µs]
change: [−41.605% −41.516% −41.425%] (p = 0.00 <
0.05)
Performance has improved.
Found 14 outliers among 100 measurements (14.00%)
4 (4.00%) low severe
3 (3.00%) low mild
5 (5.00%) high mild
2 (2.00%) high severe
cast_string_to_decimal/ansi/decimal_18_2
time: [191.08 µs 191.15 µs 191.25 µs]
change: [−36.908% −36.846% −36.785%] (p = 0.00 <
0.05)
Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
1 (1.00%) low mild
3 (3.00%) high mild
4 (4.00%) high severe
cast_string_to_decimal/try/decimal_38_10
time: [156.94 µs 157.14 µs 157.42 µs]
change: [−40.772% −40.660% −40.556%] (p = 0.00 <
0.05)
Performance has improved.
Found 14 outliers among 100 measurements (14.00%)
6 (6.00%) low mild
3 (3.00%) high mild
5 (5.00%) high severe
cast_string_to_decimal/try/decimal_18_2
time: [192.19 µs 192.30 µs 192.46 µs]
change: [−36.697% −36.607% −36.524%] (p = 0.00 <
0.05)
Performance has improved.
Found 3 outliers among 100 measurements (3.00%)
1 (1.00%) high mild
2 (2.00%) high severe
```
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