neilconway opened a new pull request, #21468:
URL: https://github.com/apache/datafusion/pull/21468
## Which issue does this PR close?
- Closes #21467.
## Rationale for this change
This PR implements three distinct optimizations:
1. `lcm` was computing the result NULL buffer iteratively. This is
relatively slow. Switching to Arrow's `try_binary` kernel both makes the
implementation more concise and also improves performance by computing the
result NULL buffer via the bitwise union of the input NULL buffers.
2. The `gcd` scalar arg path was doing similarly; switching to Arrow's
`try_unary` yields a similar speedup.
3. For the `gcd` scalar path, computing the GCD can only fail in a few edge
cases (e.g., `gcd(i64::MIN, i64::MIN)`). It is cheap to check for these
edge-cases; for most `gcd` inputs, we can use Arrow's `unary` kernel instead of
`try_unary`. The former is more efficient because it allows LLVM to vectorize
the code more effectively.
Benchmarks (ARM64):
```
- gcd array and scalar: 2.9ms → 2.2ms, -25% faster
- lcm both array: 2.7ms → 2.0ms, -26% faster
```
## What changes are included in this PR?
* Add benchmark for `lcd`
* Improve SLT test coverage
* Move Rust unit test for `lcd` to SLT
* Optimize `lcd` and `gcm` NULL handling
* Optimize `gcm` to avoid overhead for edge cases
## Are these changes tested?
Yes.
## Are there any user-facing changes?
No.
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