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strconv: ParseInt, ParseFloat use two loops instead of one #33330

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sarnold64 opened this issue Jul 28, 2019 · 1 comment
Closed

strconv: ParseInt, ParseFloat use two loops instead of one #33330

sarnold64 opened this issue Jul 28, 2019 · 1 comment
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Performance
Milestone
Go1.14

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@sarnold64
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What version of Go are you using (go version)?

$ go version
go version devel +919594830f Tue Jul 23 23:42:43 2019 +0000 darwin/amd64

Does this issue reproduce with the latest release?

Yes, see version

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/sarnold64/Library/Caches/go-build"
GOENV="/Users/sarnold64/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/sarnold64/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/Users/sarnold64/golang/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/Users/sarnold64/golang/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/sarnold64/golang/go/src/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/5s/zkkc95rs08731f9t6df3fvsc0000gr/T/go-build178433439=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I noticed that strconv takes more time than it needs to for ParseInt and ParseFloat because it loops over the input twice, once in underscoreOK and once to do the parsing.

What did you expect to see?

One loop

What did you see instead?

Two loops

I was playing around with pprof after the gophercon talks and saw this looking suspicious.

Some performance results on my laptop after fixing:

name                   old time/op  new time/op  delta
ParseInt/Pos/7bit-12   19.0ns ± 3%  12.1ns ± 0%  -36.58%  (p=0.000 n=6+5)
ParseInt/Pos/26bit-12  28.5ns ± 0%  18.4ns ± 2%  -35.58%  (p=0.002 n=6+6)
ParseInt/Pos/31bit-12  32.4ns ± 1%  20.9ns ± 1%  -35.71%  (p=0.002 n=6+6)
ParseInt/Pos/56bit-12  47.0ns ± 2%  29.3ns ± 1%  -37.70%  (p=0.002 n=6+6)
ParseInt/Pos/63bit-12  50.9ns ± 2%  32.0ns ± 1%  -37.24%  (p=0.002 n=6+6)
ParseInt/Neg/7bit-12   18.3ns ± 6%  12.2ns ± 1%  -33.18%  (p=0.002 n=6+6)
ParseInt/Neg/26bit-12  28.2ns ± 3%  18.2ns ± 2%  -35.38%  (p=0.002 n=6+6)
ParseInt/Neg/31bit-12  31.4ns ± 1%  20.7ns ± 1%  -34.04%  (p=0.004 n=6+5)
ParseInt/Neg/56bit-12  45.4ns ± 0%  29.4ns ± 1%  -35.17%  (p=0.004 n=5+6)
ParseInt/Neg/63bit-12  49.4ns ± 1%  32.0ns ± 1%  -35.30%  (p=0.002 n=6+6)

name                   old time/op  new time/op  delta
Atof64Decimal-12       30.1ns ± 1%  25.4ns ± 1%  -15.75%  (p=0.002 n=6+6)
Atof64Float-12         38.3ns ± 1%  31.5ns ± 0%  -17.84%  (p=0.000 n=6+5)
Atof64FloatExp-12      63.1ns ± 0%  53.9ns ± 0%  -14.53%  (p=0.002 n=6+6)
Atof64Big-12            113ns ± 0%    96ns ± 2%  -14.85%  (p=0.010 n=4+6)
Atof64RandomBits-12     180ns ±10%   160ns ±16%  -11.36%  (p=0.028 n=6+6)
Atof64RandomFloats-12   123ns ± 2%   102ns ± 1%  -17.03%  (p=0.002 n=6+6)
Atof32Decimal-12       31.4ns ± 0%  25.4ns ± 1%  -18.86%  (p=0.002 n=6+6)
Atof32Float-12         36.5ns ± 0%  29.4ns ± 0%  -19.40%  (p=0.008 n=5+5)
Atof32FloatExp-12      67.0ns ± 0%  56.6ns ± 0%  -15.58%  (p=0.008 n=5+5)
Atof32Random-12        90.6ns ± 1%  75.1ns ± 0%  -17.15%  (p=0.004 n=6+5)
@ALTree ALTree added this to the Go1.14 milestone Jul 28, 2019
@ALTree ALTree added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jul 28, 2019
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Change https://golang.org/cl/187957 mentions this issue: strconv: Speed improvement to number parsing

@golang golang deleted a comment from zhaoyuyang-x Jul 29, 2019
tomocy pushed a commit to tomocy/go that referenced this issue Sep 1, 2019
@sarnold64 @tomocy
strconv: Speed improvement to number parsing
2fb309b 
Run underscore validation only if we have seen underscores.

Some performance results on my laptop:
name                   old time/op  new time/op  delta
Atof64Decimal-12       30.5ns ± 0%  23.8ns ± 0%  -22.02%  (p=0.016 n=5+4)
Atof64Float-12         39.0ns ± 0%  28.7ns ± 0%  -26.39%  (p=0.002 n=6+6)
Atof64FloatExp-12      64.4ns ± 1%  54.4ns ± 1%  -15.65%  (p=0.002 n=6+6)
Atof64Big-12            115ns ± 1%    87ns ± 1%  -24.45%  (p=0.002 n=6+6)
Atof64RandomBits-12     187ns ±14%   156ns ±19%  -16.46%  (p=0.032 n=6+6)
Atof64RandomFloats-12   126ns ± 0%   105ns ± 1%  -16.65%  (p=0.000 n=6+5)
Atof32Decimal-12       32.0ns ± 1%  24.0ns ± 1%  -24.97%  (p=0.002 n=6+6)
Atof32Float-12         37.1ns ± 1%  27.0ns ± 1%  -27.42%  (p=0.002 n=6+6)
Atof32FloatExp-12      68.4ns ± 1%  54.2ns ± 1%  -20.77%  (p=0.002 n=6+6)
Atof32Random-12        92.0ns ± 1%  77.4ns ± 0%  -15.81%  (p=0.000 n=6+5)
ParseInt/Pos/7bit-12   19.4ns ± 1%  13.8ns ±10%  -28.94%  (p=0.002 n=6+6)
ParseInt/Pos/26bit-12  29.1ns ± 1%  19.8ns ± 2%  -31.92%  (p=0.002 n=6+6)
ParseInt/Pos/31bit-12  33.1ns ± 0%  22.3ns ± 3%  -32.62%  (p=0.004 n=5+6)
ParseInt/Pos/56bit-12  47.8ns ± 1%  30.7ns ± 1%  -35.78%  (p=0.004 n=6+5)
ParseInt/Pos/63bit-12  51.9ns ± 1%  33.4ns ± 2%  -35.49%  (p=0.002 n=6+6)
ParseInt/Neg/7bit-12   18.5ns ± 4%  13.4ns ± 3%  -27.88%  (p=0.002 n=6+6)
ParseInt/Neg/26bit-12  28.4ns ± 3%  19.7ns ± 3%  -30.38%  (p=0.002 n=6+6)
ParseInt/Neg/31bit-12  31.9ns ± 1%  21.8ns ± 2%  -31.56%  (p=0.002 n=6+6)
ParseInt/Neg/56bit-12  46.2ns ± 0%  30.6ns ± 1%  -33.73%  (p=0.004 n=5+6)
ParseInt/Neg/63bit-12  50.2ns ± 1%  33.2ns ± 1%  -33.96%  (p=0.002 n=6+6)

Fixes golang#33330

Change-Id: I119da66457c2fbaf6e88bb90cf56417a16df8f0e
Reviewed-on: https://go-review.googlesource.com/c/go/+/187957
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
t4n6a1ka pushed a commit to t4n6a1ka/go that referenced this issue Sep 5, 2019
@sarnold64 @t4n6a1ka
strconv: Speed improvement to number parsing
aa5d7a7 
Run underscore validation only if we have seen underscores.

Some performance results on my laptop:
name                   old time/op  new time/op  delta
Atof64Decimal-12       30.5ns ± 0%  23.8ns ± 0%  -22.02%  (p=0.016 n=5+4)
Atof64Float-12         39.0ns ± 0%  28.7ns ± 0%  -26.39%  (p=0.002 n=6+6)
Atof64FloatExp-12      64.4ns ± 1%  54.4ns ± 1%  -15.65%  (p=0.002 n=6+6)
Atof64Big-12            115ns ± 1%    87ns ± 1%  -24.45%  (p=0.002 n=6+6)
Atof64RandomBits-12     187ns ±14%   156ns ±19%  -16.46%  (p=0.032 n=6+6)
Atof64RandomFloats-12   126ns ± 0%   105ns ± 1%  -16.65%  (p=0.000 n=6+5)
Atof32Decimal-12       32.0ns ± 1%  24.0ns ± 1%  -24.97%  (p=0.002 n=6+6)
Atof32Float-12         37.1ns ± 1%  27.0ns ± 1%  -27.42%  (p=0.002 n=6+6)
Atof32FloatExp-12      68.4ns ± 1%  54.2ns ± 1%  -20.77%  (p=0.002 n=6+6)
Atof32Random-12        92.0ns ± 1%  77.4ns ± 0%  -15.81%  (p=0.000 n=6+5)
ParseInt/Pos/7bit-12   19.4ns ± 1%  13.8ns ±10%  -28.94%  (p=0.002 n=6+6)
ParseInt/Pos/26bit-12  29.1ns ± 1%  19.8ns ± 2%  -31.92%  (p=0.002 n=6+6)
ParseInt/Pos/31bit-12  33.1ns ± 0%  22.3ns ± 3%  -32.62%  (p=0.004 n=5+6)
ParseInt/Pos/56bit-12  47.8ns ± 1%  30.7ns ± 1%  -35.78%  (p=0.004 n=6+5)
ParseInt/Pos/63bit-12  51.9ns ± 1%  33.4ns ± 2%  -35.49%  (p=0.002 n=6+6)
ParseInt/Neg/7bit-12   18.5ns ± 4%  13.4ns ± 3%  -27.88%  (p=0.002 n=6+6)
ParseInt/Neg/26bit-12  28.4ns ± 3%  19.7ns ± 3%  -30.38%  (p=0.002 n=6+6)
ParseInt/Neg/31bit-12  31.9ns ± 1%  21.8ns ± 2%  -31.56%  (p=0.002 n=6+6)
ParseInt/Neg/56bit-12  46.2ns ± 0%  30.6ns ± 1%  -33.73%  (p=0.004 n=5+6)
ParseInt/Neg/63bit-12  50.2ns ± 1%  33.2ns ± 1%  -33.96%  (p=0.002 n=6+6)

Fixes golang#33330

Change-Id: I119da66457c2fbaf6e88bb90cf56417a16df8f0e
Reviewed-on: https://go-review.googlesource.com/c/go/+/187957
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
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