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strings: optimize ToUpper

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Handling the ASCII case inline and call unicode.ToUpper only
for non-ascii cases.

Gives good improvements for the ascii case and minor perf
degrade for non-ascii case

name                                     old time/op    new time/op    delta
ToUpper/#00                                11.7ns ± 8%     8.0ns ± 1%  -31.95%  (p=0.008 n=5+5)
ToUpper/ONLYUPPER                          45.6ns ± 5%    19.9ns ± 1%  -56.40%  (p=0.008 n=5+5)
ToUpper/abc                                77.4ns ± 1%    57.0ns ± 1%  -26.32%  (p=0.008 n=5+5)
ToUpper/AbC123                             92.1ns ± 4%    67.7ns ± 2%  -26.57%  (p=0.008 n=5+5)
ToUpper/azAZ09_                             105ns ± 6%      67ns ± 2%  -36.26%  (p=0.000 n=5+4)
ToUpper/longStrinGwitHmixofsmaLLandcAps     255ns ± 1%     140ns ± 1%  -45.01%  (p=0.029 n=4+4)
ToUpper/longɐstringɐwithɐnonasciiⱯchars     440ns ± 1%     447ns ± 0%   +1.49%  (p=0.016 n=5+4)
ToUpper/ɐɐɐɐɐ                               370ns ± 4%     366ns ± 1%     ~     (p=0.667 n=5+5)

name                                     old alloc/op   new alloc/op   delta
ToUpper/#00                                 0.00B          0.00B          ~     (all equal)
ToUpper/ONLYUPPER                           0.00B          0.00B          ~     (all equal)
ToUpper/abc                                 16.0B ± 0%      6.0B ± 0%  -62.50%  (p=0.008 n=5+5)
ToUpper/AbC123                              16.0B ± 0%     16.0B ± 0%     ~     (all equal)
ToUpper/azAZ09_                             24.0B ± 0%     16.0B ± 0%  -33.33%  (p=0.008 n=5+5)
ToUpper/longStrinGwitHmixofsmaLLandcAps     80.0B ± 0%     64.0B ± 0%  -20.00%  (p=0.008 n=5+5)
ToUpper/longɐstringɐwithɐnonasciiⱯchars     96.0B ± 0%     96.0B ± 0%     ~     (all equal)
ToUpper/ɐɐɐɐɐ                               64.0B ± 0%     64.0B ± 0%     ~     (all equal)

Ran on a machine with Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz

Updates #17859

Change-Id: I0735ac4a4a36e8a8f6cc06f2c16b871f12b4abf9
Reviewed-on: https://go-review.googlesource.com/68370
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Agniva De Sarker 2017-09-28 15:07:48 +05:30 • committed by Ilya Tocar
parent f10d99f51d
commit 13cfb15cb1
2 changed files with 43 additions and 1 deletions
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28
src/strings/strings.go
View file

@ -542,7 +542,33 @@ func Repeat(s string, count int) string {
}
// ToUpper returns a copy of the string s with all Unicode letters mapped to their upper case.
func ToUpper(s string) string { return Map(unicode.ToUpper, s) }
func ToUpper(s string) string {
isASCII, hasLower := true, false
for i := 0; i < len(s); i++ {
c := s[i]
if c >= utf8.RuneSelf {
isASCII = false
break
}
hasLower = hasLower || (c >= 'a' && c <= 'z')
}
if isASCII { // optimize for ASCII-only strings.
if !hasLower {
return s
}
b := make([]byte, len(s))
for i := 0; i < len(s); i++ {
c := s[i]
if c >= 'a' && c <= 'z' {
c -= 'a' - 'A'
}
b[i] = c
}
return string(b)
}
return Map(unicode.ToUpper, s)
}
// ToLower returns a copy of the string s with all Unicode letters mapped to their lower case.
func ToLower(s string) string { return Map(unicode.ToLower, s) }