Detangle linear indexing from non-scalar indexing #13614
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
This result holds for both 3.3 and 3.7. Failures were all unrelated. |
This removes the LinearFast special cases from non-scalar indexing. Previously, we were manually hoisting the div/rem sub2ind calculation along the indexed strides, but LLVM seems to be just as capable at performing this optimization in the cases I have tested. Even better, though, this creates a clean separation between the array indexing fallbacks: * Scalar fallbacks use `ind2sub` and `sub2ind` to compute the required number of indices that the custom type must implement. * Non-scalar fallbacks simply "unwrap" the elements from AbstractArrays and use scalar indexing with the indices that were provided. * (CartesianIndices are also expanded to individual integers, but that is a smaller detail.) In all cases that I've tried, I've been unable to measure a performance difference. Indeed, the LLVM IR looks identical in my spot-checks, too.
mbauman
added a commit
that referenced
this pull request
Oct 16, 2015
Detangle linear indexing from non-scalar indexing
|
Given But your comment in the code & above seems to imply that LLVM is figuring out the |
mbauman
added a commit
to mbauman/julia
that referenced
this pull request
Jan 11, 2016
Back in JuliaLang#13614 I changed the signature of _unsafe_getindex!, but I failed to update the BitArray methods... so they were just using the generic definitions. This is a very simple fix to restore the indexing performance for BitArrays.
This was referenced Jan 11, 2016
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Outdated suggestions cannot be applied.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.
This removes the LinearFast special cases from non-scalar indexing. Previously, we were manually hoisting the div/rem sub2ind calculation along the indexed strides, but LLVM seems to be just as capable at performing this optimization in the cases I have tested. Even better, though, this creates a clean separation between the array indexing fallbacks:
ind2subandsub2indto compute the required number of indices that the custom type must implement (as determined byBase.linearindexing).In all cases that I've tried, I've been unable to measure a performance difference. Indeed, the LLVM IR looks identical in my spot-checks, too.