A linear algorithm for _.flatten. #573
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
Massive speedups on _.flatten for large, deep arrays.
jashkenas
added a commit
that referenced
this pull request
Apr 30, 2012
A linear algorithm for _.flatten.
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Outdated suggestions cannot be applied.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.
Gives massive speedups on _.flatten for large, deep arrays, see http://jsperf.com/underscore-flatten-quadratic.
The trouble was the .concat call, which constructs a new array each time it's called. Swapping it out for the .push method makes it linear.
I also added a performance test for flatten, to catch this in case this comes up again.