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bytes, strings: speed up TrimSpace 4-5x for common ASCII cases #29122

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benhoyt opened this Issue Dec 6, 2018 · 1 comment

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benhoyt commented Dec 6, 2018

Per thread on golang-dev, I recently found that strings.TrimSpace is quite slow on a lot of common inputs, because it doesn't have a fast path for ASCII strings.

Adding a fast path for ASCII speeds it up 4-5x for ASCII cases, speeds it up somewhat for partially-ASCII cases, and doesn't (noticeably) slow it down for all-non-ASCII cases. So a pretty nice win for heavy users of TrimSpace like GoAWK. :-)

Thanks @josharian for helping me simplify and improve my initial version, getting it from 2-3x as fast to 4-5x as fast. The change is at: https://go-review.googlesource.com/c/go/+/152917

This is similar to #17856, where a similar ASCII fast path was introduced for strings.Fields and bytes.Fields.

For the record, I'm using go version go1.11.2 darwin/amd64.

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gopherbot commented Dec 6, 2018

Change https://golang.org/cl/152917 mentions this issue: Speed up TrimSpace 4-5x for common ASCII cases

@bcmills bcmills added the Performance label Dec 6, 2018

@bcmills bcmills added this to the Go1.13 milestone Dec 6, 2018

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