[SPARK-58682][DOCS] Update outdated OpenHashMap/OpenHashSet performance claims - #57885
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[SPARK-58682][DOCS] Update outdated OpenHashMap/OpenHashSet performance claims#57885dongjoon-hyun wants to merge 1 commit into
OpenHashMap/OpenHashSet performance claims#57885dongjoon-hyun wants to merge 1 commit into
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Could you review this doc-only PR, @LuciferYang ? |
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Thank you, @LuciferYang ! |
HyukjinKwon
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Aug 10, 2026
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Thank you, @HyukjinKwon . |
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…mance claims ### 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 This PR aims to update the outdated performance claims in the class documentation of `OpenHashMap` and `OpenHashSet`, based on the results of `OpenHashMapBenchmark` added by SPARK-58678.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 Closes #57885 from dongjoon-hyun/SPARK-58682. Authored-by: Dongjoon Hyun <dongjoon@apache.org> Signed-off-by: Dongjoon Hyun <dongjoon@apache.org> (cherry picked from commit 5adcd21) Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
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…mance claims ### 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 Closes #57885 from dongjoon-hyun/SPARK-58682. Authored-by: Dongjoon Hyun <dongjoon@apache.org> Signed-off-by: Dongjoon Hyun <dongjoon@apache.org> (cherry picked from commit 5adcd21) Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
dongjoon-hyun
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Aug 10, 2026
…mance claims ### 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 Closes #57885 from dongjoon-hyun/SPARK-58682. Authored-by: Dongjoon Hyun <dongjoon@apache.org> Signed-off-by: Dongjoon Hyun <dongjoon@apache.org> (cherry picked from commit 5adcd21) Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
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What changes were proposed in this pull request?
This PR aims to update the outdated performance claims in the class documentation of
OpenHashMapandOpenHashSet, based on the results ofOpenHashMapBenchmarkaddedby SPARK-58678.
OpenHashMap: replaced the claim "about 5X faster than java.util.HashMap" with anaccurate description: it uses much less space and is competitive for aggregation
workloads (
changeValue), whilejava.util.HashMapis faster for pure insertionsand lookups on modern JDKs.
OpenHashSet: replaced the unqualified claim "much faster than Java's standardHashSet" 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:
java.util.HashMapis 4.6X, 5.5X, 6.5X faster on Java 17, 21, and 25,respectively.
java.util.HashMapis about 2X faster.changeValue/merge):OpenHashMapis slightly faster.Since the benchmark's insert/lookup paths with object keys effectively measure
OpenHashSetas well, its unqualified "much faster" claim is also updated. Thememory advantage (about 2.2x less for
String -> Longentries) remains true and iskept.
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