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Nigel Tao a2eb53c571 strconv: use the Eisel-Lemire ParseFloat algorithm
Also fix BenchmarkAtof64Random* to initialize the test data when none
of the TestAtof* tests are run.

Passing "go test -test.count=5 -test.run=xxx -test.bench=Atof64" on to
benchstat:

name                  old time/op  new time/op  delta
Atof64Decimal-4       47.9ns ± 0%  48.3ns ± 1%     ~     (p=0.238 n=4+5)
Atof64Float-4         58.3ns ± 3%  57.7ns ± 0%     ~     (p=0.151 n=5+5)
Atof64FloatExp-4       107ns ± 0%    71ns ± 1%  -33.89%  (p=0.016 n=4+5)
Atof64Big-4            163ns ± 0%   166ns ± 2%     ~     (p=0.159 n=4+5)
Atof64RandomBits-4     299ns ± 1%   166ns ± 1%  -44.41%  (p=0.008 n=5+5)
Atof64RandomFloats-4   188ns ± 1%   144ns ± 0%  -23.03%  (p=0.008 n=5+5)

The canada.json file from github.com/miloyip/nativejson-benchmark is
full of geospatial coordinates (i.e. numbers). With this program:

    src, _ := ioutil.ReadFile("canada.json")
    for i := 0; i < 5; i++ {
        now := time.Now()
        for j := 0; j < 10; j++ {
            dst := interface{}(nil)
            if err := json.Unmarshal(src, &dst); err != nil {
                log.Fatal(err)
            }
        }
        fmt.Println(time.Since(now))
    }

Median of the 5 printed numbers, lower is better.
Before: 760.819549ms
After:  702.651646ms
Ratio:  1.08x

The new detailedPowersOfTen table weighs in at 596 * 16 = 9536 bytes,
but some of that weight gain can be clawed back, in a follow-up commit,
that folds in the existing powersOfTen table in extfloat.go.

RELNOTE=yes

Change-Id: I3953110deaa1f5f6941e88e8417c4665b649ed80
Reviewed-on: https://go-review.googlesource.com/c/go/+/260858
Run-TryBot: Nigel Tao <nigeltao@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Nigel Tao <nigeltao@golang.org>
2020-10-17 00:26:52 +00:00
.github .github: add link to questions in ISSUE_TEMPLATE 2020-01-06 17:05:31 +00:00
api text/template: add CommentNode to template parse tree 2020-08-28 21:45:12 +00:00
doc strconv: use the Eisel-Lemire ParseFloat algorithm 2020-10-17 00:26:52 +00:00
lib/time lib/time, time, time/tzdata: use slim tz data format 2020-10-14 09:00:41 +00:00
misc cmd/link: support PIE internal linking on darwin/amd64 2020-10-14 00:19:23 +00:00
src strconv: use the Eisel-Lemire ParseFloat algorithm 2020-10-17 00:26:52 +00:00
test cmd/compile: use staticValue for inlining logic 2020-10-15 18:35:44 +00:00
.gitattributes all: treat all files as binary, but check in .bat with CRLF 2020-06-08 15:31:43 +00:00
.gitignore .gitignore: ignore src/cmd/dist/dist 2017-10-28 21:55:49 +00:00
AUTHORS A+C: add Kush Patel (corporate CLA for Hootsuite Inc) 2020-07-08 00:10:44 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
CONTRIBUTORS CONTRIBUTORS: update for the Go 1.15 release 2020-08-10 21:51:48 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
LICENSE
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README.md README: linkify some paths 2018-06-06 18:07:01 +00:00
robots.txt
SECURITY.md SECURITY.md: update go versions 2019-09-26 15:34:57 +00:00

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