strconv: replace Ryu ftoa with Dragonbox #75195

taichimaeda · 2025-08-30T07:53:22Z

Dragonbox is a faster ftoa algorithm that provides the same guarantees
as Ryu: round-trip conversion, shortest length, and correct rounding.
The author of the reference implementation has agreed to distribute
this file under Go's BSD-style license.

The new implementation has been fuzz-tested against the current
Ryu implementation in addition to the existing test suite.
Benchmarks show at least ~15-20% performance improvement.

Dragonbox only supports shortest-precision conversion, so we continue to
use Ryu-printf for fixed precision.

The following shows the relevant output from benchstat. Full benchmark
results and plots are available at:
https://github.com/taichimaeda/dragonbox-bench/

goos: darwin
goarch: arm64
pkg: strconv
cpu: Apple M1
│ old.txt │ │ sec/op │ sec/op FormatFloat/Decimal-8 FormatFloat/Float-8 FormatFloat/Exp-8 FormatFloat/NegExp-8 FormatFloat/LongExp-8 FormatFloat/Big-8 FormatFloat/BinaryExp-8 FormatFloat/32Integer-8 FormatFloat/32ExactFraction-8 FormatFloat/32Point-8 FormatFloat/32Exp-8 FormatFloat/32NegExp-8 FormatFloat/32Shortest-8 FormatFloat/Slowpath64-8 FormatFloat/SlowpathDenormal64-8 FormatFloat/ShorterIntervalCase32-8 FormatFloat/ShorterIntervalCase64-8 geomean new.txt │
vs base │
32.71n ± 14% 31.89n ± 12% ~ (p=0.165 n=10)
45.54n ± 1% 42.48n ± 0% -6.70% (p=0.000 n=10)
50.06n ± 0% 32.27n ± 1% -35.54% (p=0.000 n=10)
47.15n ± 1% 31.33n ± 0% -33.56% (p=0.000 n=10)
46.15n ± 1% 43.66n ± 0% -5.38% (p=0.000 n=10)
50.02n ± 0% 39.36n ± 0% -21.31% (p=0.000 n=10)
27.89n ± 0% 27.88n ± 1% ~ (p=0.798 n=10)
31.41n ± 0% 23.00n ± 3% -26.79% (p=0.000 n=10)
44.93n ± 1% 29.91n ± 0% -33.43% (p=0.000 n=10)
43.22n ± 1% 33.82n ± 0% -21.74% (p=0.000 n=10)
45.91n ± 0% 25.48n ± 0% -44.50% (p=0.000 n=10)
44.66n ± 0% 25.12n ± 0% -43.76% (p=0.000 n=10)
37.96n ± 0% 27.83n ± 1% -26.68% (p=0.000 n=10)
47.74n ± 2% 45.85n ± 0% -3.96% (p=0.000 n=10)
42.78n ± 1% 41.46n ± 0% -3.07% (p=0.000 n=10)
25.49n ± 2%
27.72n ± 1%
41.95n 31.89n -22.11%

Fixes #74886

gopherbot · 2025-08-30T07:57:31Z

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gopherbot · 2025-08-30T08:05:03Z

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gopherbot · 2025-08-30T08:05:04Z

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gopherbot · 2025-08-30T08:20:07Z

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gopherbot · 2025-08-31T04:04:33Z

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gopherbot · 2025-08-31T11:37:19Z

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gopherbot · 2025-09-01T01:06:27Z

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gopherbot · 2025-09-02T11:12:04Z

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Dragonbox is a faster ftoa algorithm that provides the same guarantees as Ryu: round-trip conversion, shortest length, and correct rounding. The author of the reference implementation has agreed to distribute this file under Go's BSD-style license. The new implementation has been fuzz-tested against the current Ryu implementation in addition to the existing test suite. Benchmarks show at least ~15-20% performance improvement. Dragonbox only supports shortest-precision conversion, so we continue to use Ryu-printf for fixed precision. The following shows the relevant output from benchstat. Full benchmark results and plots are available at: https://github.com/taichimaeda/dragonbox-bench/ goos: darwin goarch: arm64 pkg: strconv cpu: Apple M1 │ old.txt │ new.txt │ │ sec/op │ sec/op vs base │ FormatFloat/Decimal-8 32.71n ± 14% 31.89n ± 12% ~ (p=0.165 n=10) FormatFloat/Float-8 45.54n ± 1% 42.48n ± 0% -6.70% (p=0.000 n=10) FormatFloat/Exp-8 50.06n ± 0% 32.27n ± 1% -35.54% (p=0.000 n=10) FormatFloat/NegExp-8 47.15n ± 1% 31.33n ± 0% -33.56% (p=0.000 n=10) FormatFloat/LongExp-8 46.15n ± 1% 43.66n ± 0% -5.38% (p=0.000 n=10) FormatFloat/Big-8 50.02n ± 0% 39.36n ± 0% -21.31% (p=0.000 n=10) FormatFloat/BinaryExp-8 27.89n ± 0% 27.88n ± 1% ~ (p=0.798 n=10) FormatFloat/32Integer-8 31.41n ± 0% 23.00n ± 3% -26.79% (p=0.000 n=10) FormatFloat/32ExactFraction-8 44.93n ± 1% 29.91n ± 0% -33.43% (p=0.000 n=10) FormatFloat/32Point-8 43.22n ± 1% 33.82n ± 0% -21.74% (p=0.000 n=10) FormatFloat/32Exp-8 45.91n ± 0% 25.48n ± 0% -44.50% (p=0.000 n=10) FormatFloat/32NegExp-8 44.66n ± 0% 25.12n ± 0% -43.76% (p=0.000 n=10) FormatFloat/32Shortest-8 37.96n ± 0% 27.83n ± 1% -26.68% (p=0.000 n=10) FormatFloat/Slowpath64-8 47.74n ± 2% 45.85n ± 0% -3.96% (p=0.000 n=10) FormatFloat/SlowpathDenormal64-8 42.78n ± 1% 41.46n ± 0% -3.07% (p=0.000 n=10) FormatFloat/ShorterIntervalCase32-8 25.49n ± 2% FormatFloat/ShorterIntervalCase64-8 27.72n ± 1% geomean 41.95n 31.89n -22.11% Fixes golang#74886

gopherbot · 2025-09-02T11:28:17Z

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gopherbot · 2025-09-02T11:36:26Z

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gopherbot · 2025-09-02T13:22:49Z

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Patch Set 8: Run-TryBot+1

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gopherbot · 2025-09-02T13:22:49Z

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gopherbot · 2025-09-03T12:27:10Z

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austinderek mentioned this pull request Aug 30, 2025

strconv: replace Ryu ftoa with Dragonbox PullRequestInc/go#56

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taichimaeda force-pushed the dragonbox branch from 379512d to 27788a0 Compare August 30, 2025 08:04

taichimaeda force-pushed the dragonbox branch from 27788a0 to c7383b6 Compare August 31, 2025 04:00

taichimaeda force-pushed the dragonbox branch from c7383b6 to 70ee13b Compare September 1, 2025 01:02

taichimaeda force-pushed the dragonbox branch from 70ee13b to 6699b0f Compare September 2, 2025 10:49

taichimaeda force-pushed the dragonbox branch from 6699b0f to a6241f7 Compare September 2, 2025 11:22

strconv: replace Ryu ftoa with Dragonbox #75195

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strconv: replace Ryu ftoa with Dragonbox #75195

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