dongjoon-hyun opened a new pull request, #57885:
URL: https://github.com/apache/spark/pull/57885
### What changes were proposed in this pull request?
This PR aims to update the outdated performance claims in the class
documentation of
`OpenHashMap` and `OpenHashSet`, based on the results of
`OpenHashMapBenchmark` added
by SPARK-58678.
- `OpenHashMap`: replaced the claim "about 5X faster than java.util.HashMap"
with an
accurate description: it uses much less space and is competitive for
aggregation
workloads (`changeValue`), while `java.util.HashMap` is faster for pure
insertions
and lookups on modern JDKs.
- `OpenHashSet`: replaced the unqualified claim "much faster than Java's
standard
HashSet" with the verifiable facts: much less memory overhead, and the
specialized
versions avoid boxing of primitive keys.
### Why are the changes needed?
The "about 5X faster" claim dates from 2013 (pre-JDK 8).
`OpenHashMapBenchmark`
(SPARK-58678) shows that on modern JDKs the claim no longer holds:
- **Insert**: `java.util.HashMap` is 4.6X, 5.5X, 6.5X faster on Java 17, 21,
and 25,
respectively.
- **Lookup**: `java.util.HashMap` is about 2X faster.
- **Aggregate** (`changeValue`/`merge`): `OpenHashMap` is slightly faster.
Since the benchmark's insert/lookup paths with object keys effectively
measure
`OpenHashSet` as well, its unqualified "much faster" claim is also updated.
The
memory advantage (about 2.2x less for `String -> Long` entries) remains true
and is
kept.
### Does this PR introduce _any_ user-facing change?
No. This is a comment-only change.
### How was this patch tested?
Pass the CIs. This is a comment-only change with no behavior change.
### Was this patch authored or co-authored using generative AI tooling?
Generated-by: Claude Fable 5
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