[SR-13353] SIMD instructions slow: Calls to IndexingIterator.next() #55793
Labels
bug
A deviation from expected or documented behavior. Also: expected but undesirable behavior.
performance
simd
standard library
Area: Standard library umbrella
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Environment
Xcode: Version 12.0 beta 3 (12A8169g)
MacBook Pro (16-inch, 2019) - 2,4 GHz 8-Core Intel Core i9
Additional Detail from JIRA
Watchers: @shahmishal
md5: a9b0f1c4918239714c91107417976ce1
Issue Description:
Today I've been toying around with `UUID`s. I wanted to see if I can write a fast Swift UUID parser (without Foundation). To achieve this I used the SIMD Swift instructions. Interestingly the performance was about 6times slower than using `uuid_parse` (from Darwin) and more than ten times slower compared to a simple parsing loop. (The code is attached)
Parsing UUIDs: 1000000-----------------------------uuid_parse | took: 0.39703sLoop UUIDKit | took: 0.22107sSIMD UUIDKit | took: 2.65504sFoundation | took: 0.54979sLooking into the performance with Instruments, I've found that there are a lot of calls to `specialized IndexingIterator.next()`. Maybe I'm missing something here, but I wonder why there is an `Iterator` in use?
I assume that this might be related to: https://bugs.swift.org/browse/SR-12777
If you have any questions please reach out. My technical skills (assembler and stuff) are limited though.
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