Improve [U]Int128 string conversion performance. #65508
Open
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
String to (U)Int128 conversions are 9 times faster. (U)Int128 to String conversions are 25 times faster.
stephentyrone
requested changes
Jun 12, 2023
stdlib/public/core/Int128.swift.gyb
Outdated
| private static func times<T:FixedWidthInteger>( | ||
| x: T, timesRadix radix: UInt64, toPower n: Int) -> T { | ||
| // calculate the powers of the radix and store in a table | ||
| if powers.isEmpty || powers.first! != radix { |
There was a problem hiding this comment.
This has an obvious toctou race condition, as well as a more subtle race condition on targets without total store ordering. I don't think that it's actually possible to use a lazily computed table of powers like this without an explicit lock. Given what the expected distribution of radices looks like, simply covering power-of-two bases with a precomputed table for base 10 would be a much more attractive solution.
There was a problem hiding this comment.
Thanks for the feedback! Will do a precomputed table for base 10 and powers of 2.
There was a problem hiding this comment.
@stephentyrone, latest update should fix this race condition issue.
Fixed toctou race condition, as well as a more subtle race condition on targets without total store ordering.
Set the radix during power calculations.
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Outdated suggestions cannot be applied.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.
String to [U]Int128 conversions are 9 times faster.
[U]Int128 to String conversions are 25 times faster.
@stephentyrone suggested my [U]Int128 changes would be better placed in the standard library.
[U]Int128 probably fits better in the standard library itself (there's already a partial implementation there to support Duration.