Optimize away compare256 for short matches #284
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Author
|
I'm posting this for discussion because it produces mixed results on my test system:
Whether it helps is probably dependent on the CPU and the input data. |
brian-pane
commented
Jan 11, 2025
Comment on lines
+195
to
+196
| if best_len < core::mem::size_of::<u64>() { | ||
| let scan_val = u64::from_ne_bytes( |
Author
There was a problem hiding this comment.
I also tried if best_len < 32 { followed by the equivalent AVX2 implementation (similar to how compare32 processes each 32=byte chunk), but it was slower overall.
folkertdev
approved these changes
Jan 14, 2025
Member
folkertdev
left a comment
folkertdev
left a comment
There was a problem hiding this comment.
I think a slightly higher instruction count (correctly predicted branches?) is totally acceptable if we get a performance boost, especially because levels 3,4, 7 and 8 are rarely used in practice.
And the gains at level 2 and 9 are very real, so I think this is OK. Thanks!
nmoinvaz
added a commit
to nmoinvaz/zlib-ng
that referenced
this pull request
Nov 28, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
No description provided.