strings: use Builder in Map #26304
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ianlancetaylor
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Change https://golang.org/cl/122875 mentions this issue: |
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There is a performance issue that I ran across when trying to use the Builder. The last loop which copies by byte or rune should be able to to just use builder.WriteRune(r), however, it was always ~30% slower to do so. |
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Builder is not always faster, in particular for this specified case: https://groups.google.com/forum/#!topic/golang-nuts/I6Ch7hMEQLk |
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@fraenkel want to file an independent issue? |
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@josharian We did determine its due to inlining. There is also another issue around which is focused on strings vs []bytes, #26264 |
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Is this issue still relevant? Should I check it out? |
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Change https://golang.org/cl/137575 mentions this issue: |
gopherbot
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Sep 26, 2018
Map was optimized to use Builder in 45c7d80, which avoided the []byte to string converstion. This left the ToUpper and ToLower ASCII fast path with an extra allocation over Map. name old time/op new time/op delta ToUpper/#00-12 3.59ns ± 4% 3.71ns ± 1% ~ (p=0.056 n=5+5) ToUpper/ONLYUPPER-12 11.8ns ± 2% 10.5ns ± 2% -10.85% (p=0.008 n=5+5) ToUpper/abc-12 31.8ns ± 1% 25.3ns ± 1% -20.40% (p=0.008 n=5+5) ToUpper/AbC123-12 46.2ns ± 7% 31.9ns ± 8% -30.89% (p=0.008 n=5+5) ToUpper/azAZ09_-12 47.1ns ± 8% 32.6ns ± 4% -30.77% (p=0.008 n=5+5) ToUpper/longStrinGwitHmixofsmaLLandcAps-12 137ns ±15% 104ns ±11% -24.11% (p=0.008 n=5+5) ToUpper/longɐstringɐwithɐnonasciiⱯchars-12 231ns ± 1% 228ns ± 1% ~ (p=0.079 n=5+5) ToUpper/ɐɐɐɐɐ-12 207ns ± 3% 206ns ± 1% ~ (p=0.913 n=5+5) ToUpper/a\u0080\U0010ffff-12 90.8ns ± 1% 89.6ns ± 1% -1.30% (p=0.024 n=5+5) ToLower/#00-12 3.59ns ± 1% 4.26ns ± 2% +18.66% (p=0.008 n=5+5) ToLower/abc-12 6.32ns ± 1% 6.62ns ± 1% +4.72% (p=0.008 n=5+5) ToLower/AbC123-12 45.0ns ±13% 31.5ns ± 4% -29.89% (p=0.008 n=5+5) ToLower/azAZ09_-12 48.8ns ± 6% 33.2ns ± 3% -31.91% (p=0.008 n=5+5) ToLower/longStrinGwitHmixofsmaLLandcAps-12 149ns ±13% 98ns ± 8% -34.30% (p=0.008 n=5+5) ToLower/LONGⱯSTRINGⱯWITHⱯNONASCIIⱯCHARS-12 237ns ± 4% 237ns ± 2% ~ (p=0.635 n=5+5) ToLower/ⱭⱭⱭⱭⱭ-12 181ns ± 1% 181ns ± 1% ~ (p=0.762 n=5+5) ToLower/A\u0080\U0010ffff-12 90.6ns ± 1% 92.5ns ± 1% +2.05% (p=0.016 n=5+5) name old alloc/op new alloc/op delta ToUpper/#00-12 0.00B 0.00B ~ (all equal) ToUpper/ONLYUPPER-12 0.00B 0.00B ~ (all equal) ToUpper/abc-12 6.00B ± 0% 3.00B ± 0% -50.00% (p=0.008 n=5+5) ToUpper/AbC123-12 16.0B ± 0% 8.0B ± 0% -50.00% (p=0.008 n=5+5) ToUpper/azAZ09_-12 16.0B ± 0% 8.0B ± 0% -50.00% (p=0.008 n=5+5) ToUpper/longStrinGwitHmixofsmaLLandcAps-12 64.0B ± 0% 32.0B ± 0% -50.00% (p=0.008 n=5+5) ToUpper/longɐstringɐwithɐnonasciiⱯchars-12 48.0B ± 0% 48.0B ± 0% ~ (all equal) ToUpper/ɐɐɐɐɐ-12 48.0B ± 0% 48.0B ± 0% ~ (all equal) ToUpper/a\u0080\U0010ffff-12 16.0B ± 0% 16.0B ± 0% ~ (all equal) ToLower/#00-12 0.00B 0.00B ~ (all equal) ToLower/abc-12 0.00B 0.00B ~ (all equal) ToLower/AbC123-12 16.0B ± 0% 8.0B ± 0% -50.00% (p=0.008 n=5+5) ToLower/azAZ09_-12 16.0B ± 0% 8.0B ± 0% -50.00% (p=0.008 n=5+5) ToLower/longStrinGwitHmixofsmaLLandcAps-12 64.0B ± 0% 32.0B ± 0% -50.00% (p=0.008 n=5+5) ToLower/LONGⱯSTRINGⱯWITHⱯNONASCIIⱯCHARS-12 48.0B ± 0% 48.0B ± 0% ~ (all equal) ToLower/ⱭⱭⱭⱭⱭ-12 32.0B ± 0% 32.0B ± 0% ~ (all equal) ToLower/A\u0080\U0010ffff-12 16.0B ± 0% 16.0B ± 0% ~ (all equal) name old allocs/op new allocs/op delta ToUpper/#00-12 0.00 0.00 ~ (all equal) ToUpper/ONLYUPPER-12 0.00 0.00 ~ (all equal) ToUpper/abc-12 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.008 n=5+5) ToUpper/AbC123-12 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.008 n=5+5) ToUpper/azAZ09_-12 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.008 n=5+5) ToUpper/longStrinGwitHmixofsmaLLandcAps-12 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.008 n=5+5) ToUpper/longɐstringɐwithɐnonasciiⱯchars-12 1.00 ± 0% 1.00 ± 0% ~ (all equal) ToUpper/ɐɐɐɐɐ-12 2.00 ± 0% 2.00 ± 0% ~ (all equal) ToUpper/a\u0080\U0010ffff-12 1.00 ± 0% 1.00 ± 0% ~ (all equal) ToLower/#00-12 0.00 0.00 ~ (all equal) ToLower/abc-12 0.00 0.00 ~ (all equal) ToLower/AbC123-12 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.008 n=5+5) ToLower/azAZ09_-12 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.008 n=5+5) ToLower/longStrinGwitHmixofsmaLLandcAps-12 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.008 n=5+5) ToLower/LONGⱯSTRINGⱯWITHⱯNONASCIIⱯCHARS-12 1.00 ± 0% 1.00 ± 0% ~ (all equal) ToLower/ⱭⱭⱭⱭⱭ-12 1.00 ± 0% 1.00 ± 0% ~ (all equal) ToLower/A\u0080\U0010ffff-12 1.00 ± 0% 1.00 ± 0% ~ (all equal) Updates #26304 Change-Id: I4179e21d5e60d950b925fe3ffc74b376b82812d2 GitHub-Last-Rev: 2c7c3bb GitHub-Pull-Request: #27872 Reviewed-on: https://go-review.googlesource.com/137575 Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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@robpike and I were just looking at strings.Map. It should use Builder to avoid a copy at the end in the conversion from []byte to string.
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