Wavelet transform (e.g. retouch) speedup #5205
Merged
Conversation
This file contains 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
Four 'for' loops were parallelized, but each of them runs so fast single-threaded that the threading overhead greatly exceeds any gains (resulting in massive use of CPU time for essentially no speed improvement). This patch limits threads to 2 to avoid wasting CPU time.
|
This pull request did not get any activity in the past 30 days and will be closed in 365 days if no update occurs. Please verify it has no conflicts with the master branch and rebase if needed. Mention it now if you need help or give permission to other people to finish your work. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
The discrete wavelet transform code was running essentially single-threaded, and what multithreading that did happen was basically burning CPU cycles for no gain.
This PR speeds up single-threaded performance by about 10% on SSE-capable systems, and multithreaded performance by more than a factor of two with eight or more threads. (Test was retouch module with 6 wavelet scales and a "pencil" brush on one of the scales.)