Russ Cox (Gerrit)

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Russ Cox (Gerrit)

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File src/internal/strconv/math.go

Line 70, Patchset 1 (Latest):// can be implemented by x*m where m is the multiplicative inverse of c (x*c == 1).

Russ Cox . unresolved

m*c == 1

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Russ Cox (Gerrit)

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File src/internal/strconv/ftoafixed.go

Line 81, Patchset 1 (Latest): // (This is the same trick compilers use for divison by constants.

Russ Cox . unresolved

division

Line 112, Patchset 1 (Latest): // Apply that to de by shifting, but leave one extra bit for rounding.

Russ Cox . unresolved

Multiply by 2^de by shifting...

File src/internal/strconv/math.go

Line 73, Patchset 1 (Latest):// and all the exact multiples of c map take up all of [0, maxUint64/c].

Russ Cox . unresolved

s/map take up/map to/

Line 85, Patchset 1 (Latest):// x%(c<<s) == 0 => bits.RotateLeft64(x*m, 64-s) <= maxUint64/c.

Russ Cox . unresolved

s/64-s/-s/

Line 112, Patchset 1 (Latest): {0xfee64690c913975, 0x57f5ff85e5},

Russ Cox . unresolved

0x0f...

File src/internal/strconv/testdata/testfp.txt

Line 19, Patchset 1 (Latest):# Random cases from TestFtoaRandom that broke buggy ftoaFixed.

Russ Cox . unresolved

These probably belong in ftoa_test.go instead.

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Russ Cox (Gerrit)

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Russ Cox uploaded patch set #2 to this change.

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Russ Cox (Gerrit)

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File src/internal/strconv/ftoafixed.go

Line 81, Patchset 1: // (This is the same trick compilers use for divison by constants.

Russ Cox . resolved

division

Russ Cox

Done

Line 112, Patchset 1: // Apply that to de by shifting, but leave one extra bit for rounding.

Russ Cox . resolved

Multiply by 2^de by shifting...

Russ Cox

Done

File src/internal/strconv/math.go

Line 70, Patchset 1:// can be implemented by x*m where m is the multiplicative inverse of c (x*c == 1).

Russ Cox . resolved

m*c == 1

Russ Cox

Done

Line 73, Patchset 1:// and all the exact multiples of c map take up all of [0, maxUint64/c].

Russ Cox . resolved

s/map take up/map to/

Russ Cox

Done

Line 85, Patchset 1:// x%(c<<s) == 0 => bits.RotateLeft64(x*m, 64-s) <= maxUint64/c.

Russ Cox . resolved

s/64-s/-s/

Russ Cox

Done

Line 112, Patchset 1: {0xfee64690c913975, 0x57f5ff85e5},

Russ Cox . resolved

0x0f...

Russ Cox

Done

File src/internal/strconv/testdata/testfp.txt

Line 19, Patchset 1:# Random cases from TestFtoaRandom that broke buggy ftoaFixed.

Russ Cox . resolved

These probably belong in ftoa_test.go instead.

Russ Cox

Done

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Russ Cox (Gerrit)

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Alan Donovan (Gerrit)

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File src/internal/strconv/ftoafixed.go

Line 14, Patchset 2 (Latest):// fixedFtoa formats a number of decimal digits of mant*(2^exp) into d.

Alan Donovan . unresolved

where mant > 0 and 0 < digits <= 18

Line 45, Patchset 2 (Latest): // The lower bound is strict; the upper bound is flexible.

Alan Donovan . unresolved

Not quite sure what this word means here, especially since only the lower bound uses a non-strict (inclusive) inequality.

Line 96, Patchset 2 (Latest): case 0 <= p && p <= 55:

Alan Donovan . unresolved

Whence this constant?

Line 116, Patchset 2 (Latest): dt |= bool2uint(dm&(1<<shift-1) != 0)

Alan Donovan . unresolved

Why do we set the rounding bit if any of the low order mantissa bits are nonzero?

File src/internal/strconv/math.go

Line 60, Patchset 2 (Latest):func bool2uint(b bool) uint {

Alan Donovan . resolved

[adonovan sobs on the grave of #64825]

Line 75, Patchset 2 (Latest):// This also gives a quick test for whether x is an exact multiple of c:

Alan Donovan . resolved

neat

Line 100, Patchset 2 (Latest):// div5Tab[p-1] is the multiplicative inverse of 5^p and maxUint64/5^p.

Alan Donovan . unresolved

How did you compute these? Using big.Int.ModInverse?

Line 112, Patchset 2 (Latest): {0x0fee64690c913975, 0x57f5ff85e5},

Alan Donovan . unresolved

`(1<<64 - 1) / (5*5*5*5*5*5*5*5*5*5*5)` would be self-documenting.

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Russ Cox uploaded patch set #3 to this change.

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Russ Cox (Gerrit)

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File src/internal/strconv/ftoafixed.go

Line 14, Patchset 2:// fixedFtoa formats a number of decimal digits of mant*(2^exp) into d.

Alan Donovan . resolved

where mant > 0 and 0 < digits <= 18

Russ Cox

Done

Line 45, Patchset 2: // The lower bound is strict; the upper bound is flexible.

Alan Donovan . resolved

Not quite sure what this word means here, especially since only the lower bound uses a non-strict (inclusive) inequality.

Russ Cox

Changed to:

	// The lower bound is required, but the upper bound is approximate:
	// we must not have too few digits, but we can round away extra ones.

Line 96, Patchset 2: case 0 <= p && p <= 55:

Alan Donovan . resolved

Whence this constant?

Russ Cox

Recommented:

	case 0 <= p && p <= 55:

		// Small positive powers of 10 (up to 10⁵⁵) can be represented
		// precisely in a 128-bit mantissa (5⁵⁵ ≤ 2¹²⁸), so the only truncation
		// comes from discarding the low bits of the 192-bit product.

Line 116, Patchset 2: dt |= bool2uint(dm&(1<<shift-1) != 0)

Alan Donovan . resolved

Why do we set the rounding bit if any of the low order mantissa bits are nonzero?

Russ Cox

dt is the truncated bit not the rounding bit. Recommented:

	// After the shift, the "integer part" of dm is dm>>1,
	// the "rounding bit" (the first fractional bit) is dm&1,
	// and the "truncated bit" (have any bits been discarded?) is dt.
	shift := -de - 1


	dt |= bool2uint(dm&(1<<shift-1) != 0)

	dm >>= shift

File src/internal/strconv/math.go

Line 100, Patchset 2:// div5Tab[p-1] is the multiplicative inverse of 5^p and maxUint64/5^p.

Alan Donovan . resolved

How did you compute these? Using big.Int.ModInverse?

Russ Cox

The usual: go tool compile -S.
😊

Line 112, Patchset 2: {0x0fee64690c913975, 0x57f5ff85e5},

Alan Donovan . resolved

`(1<<64 - 1) / (5*5*5*5*5*5*5*5*5*5*5)` would be self-documenting.

Russ Cox

Done although the lines are quite long.

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Gopher Robot submitted the change

Change information

Commit message:

internal/strconv: extract fixed-precision ftoa from ftoaryu.go

The fixed-precision ftoa algorithm is not actually
documented in the Ryū paper, and it is fairly
straightforward: multiply by a power of 10 to get
an integer that contains the digits we need.
There is also no need for separate float32 and float64
implementations.

This CL implements a new fixedFtoa, separate from Ryū.
The overall algorithm is the same, but the new code
is simpler, faster, and better documented.

Now ftoaryu.go is only about shortest-output formatting,
so if and when yet another algorithm comes along, it will
be clearer what should be replaced (all of ftoaryu.go)
and what should not (all of ftoafixed.go).

benchmark \ host                  linux-arm64    local  linux-amd64       s7  linux-386  s7:GOARCH=386
                                      vs base  vs base      vs base  vs base    vs base        vs base
AppendFloat/Decimal                    -0.18%        ~            ~   -0.68%     +0.49%         -0.79%
AppendFloat/Float                      +0.09%        ~       +1.50%   +0.84%     -0.37%         -0.69%
AppendFloat/Exp                        -0.51%        ~            ~   +1.20%     -1.27%         -1.01%
AppendFloat/NegExp                     -1.01%        ~       +3.43%   +1.35%     -2.33%              ~
AppendFloat/LongExp                    -1.22%   +0.77%            ~        ~     -1.48%              ~
AppendFloat/Big                        -2.07%        ~       -2.07%   -1.97%     -2.89%         -2.93%
AppendFloat/BinaryExp                  -0.28%   +1.06%            ~   +1.35%     -0.64%         -1.64%
AppendFloat/32Integer                       ~        ~            ~   -0.79%          ~         -0.66%
AppendFloat/32ExactFraction            -0.50%        ~       +5.69%        ~     -1.24%         +0.69%
AppendFloat/32Point                         ~   -1.19%       +2.59%   +1.03%     -1.37%         +0.80%
AppendFloat/32Exp                      -3.39%   -2.79%       -8.36%   -0.94%     -5.72%         -5.92%
AppendFloat/32NegExp                   -0.63%        ~            ~   +0.98%     -1.34%         -0.73%
AppendFloat/32Shortest                 -1.00%   +1.36%       +2.94%        ~          ~              ~
AppendFloat/32Fixed8Hard               -5.91%  -12.45%       -6.62%        ~    +18.46%        +11.61%
AppendFloat/32Fixed9Hard               -6.53%  -11.35%       -6.01%   -0.97%    -18.31%         -9.16%
AppendFloat/64Fixed1                  -13.84%  -16.90%      -13.13%  -10.71%    -24.52%        -18.94%
AppendFloat/64Fixed2                  -11.12%  -16.97%      -12.13%   -9.88%    -22.73%        -15.48%
AppendFloat/64Fixed2.5                -21.98%  -20.75%      -19.08%  -14.74%    -28.11%        -24.92%
AppendFloat/64Fixed3                  -11.53%  -16.21%      -10.75%   -7.53%    -23.11%        -15.78%
AppendFloat/64Fixed4                  -12.89%  -12.36%      -11.07%   -9.79%    -14.51%        -13.44%
AppendFloat/64Fixed5Hard              -47.62%  -38.59%      -40.83%  -37.06%    -60.51%        -55.29%
AppendFloat/64Fixed12                  -7.40%        ~       -8.56%   -4.31%    -13.82%         -8.61%
AppendFloat/64Fixed16                  -9.10%   -8.95%       -6.92%   -3.92%    -12.99%         -9.03%
AppendFloat/64Fixed12Hard              -9.14%   -5.24%       -6.23%   -4.82%    -13.58%         -8.99%
AppendFloat/64Fixed17Hard              -6.80%        ~       -4.03%   -2.84%    -19.81%        -10.27%
AppendFloat/64Fixed18Hard              -0.12%        ~            ~        ~          ~              ~
AppendFloat/64FixedF1                       ~        ~            ~        ~     -0.40%         +2.72%
AppendFloat/64FixedF2                  -0.18%        ~       -1.98%   -0.95%          ~         +1.25%
AppendFloat/64FixedF3                  -0.29%        ~            ~        ~          ~         +1.22%
AppendFloat/Slowpath64                 -1.16%        ~            ~        ~          ~         -2.16%
AppendFloat/SlowpathDenormal64         -1.09%        ~            ~   -0.88%     -0.83%              ~

host: linux-arm64
goos: linux
goarch: arm64
pkg: internal/strconv
cpu: unknown
                                 │ 14b7e09f493  │             f9bf7fcb8e2             │
                                 │    sec/op    │   sec/op     vs base                │
AppendFloat/Decimal-8               60.35n ± 0%   60.24n ± 0%   -0.18% (p=0.000 n=20)
AppendFloat/Float-8                 88.83n ± 0%   88.91n ± 0%   +0.09% (p=0.000 n=20)
AppendFloat/Exp-8                   93.55n ± 0%   93.06n ± 0%   -0.51% (p=0.000 n=20)
AppendFloat/NegExp-8                94.01n ± 0%   93.06n ± 0%   -1.01% (p=0.000 n=20)
AppendFloat/LongExp-8              101.00n ± 0%   99.77n ± 0%   -1.22% (p=0.000 n=20)
AppendFloat/Big-8                   106.1n ± 0%   103.9n ± 0%   -2.07% (p=0.000 n=20)
AppendFloat/BinaryExp-8             47.48n ± 0%   47.35n ± 0%   -0.28% (p=0.000 n=20)
AppendFloat/32Integer-8             60.45n ± 0%   60.43n ± 0%        ~ (p=0.150 n=20)
AppendFloat/32ExactFraction-8       86.65n ± 0%   86.22n ± 0%   -0.50% (p=0.000 n=20)
AppendFloat/32Point-8               83.26n ± 0%   83.21n ± 0%        ~ (p=0.046 n=20)
AppendFloat/32Exp-8                 92.55n ± 0%   89.42n ± 0%   -3.39% (p=0.000 n=20)
AppendFloat/32NegExp-8              87.89n ± 0%   87.34n ± 0%   -0.63% (p=0.000 n=20)
AppendFloat/32Shortest-8            77.05n ± 0%   76.28n ± 0%   -1.00% (p=0.000 n=20)
AppendFloat/32Fixed8Hard-8          55.73n ± 0%   52.44n ± 0%   -5.91% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-8          64.80n ± 0%   60.57n ± 0%   -6.53% (p=0.000 n=20)
AppendFloat/64Fixed1-8              53.72n ± 0%   46.29n ± 0%  -13.84% (p=0.000 n=20)
AppendFloat/64Fixed2-8              52.64n ± 0%   46.79n ± 0%  -11.12% (p=0.000 n=20)
AppendFloat/64Fixed2.5-8            56.01n ± 0%   43.70n ± 0%  -21.98% (p=0.000 n=20)
AppendFloat/64Fixed3-8              53.38n ± 0%   47.23n ± 0%  -11.53% (p=0.000 n=20)
AppendFloat/64Fixed4-8              50.62n ± 0%   44.10n ± 0%  -12.89% (p=0.000 n=20)
AppendFloat/64Fixed5Hard-8          98.94n ± 0%   51.82n ± 0%  -47.62% (p=0.000 n=20)
AppendFloat/64Fixed12-8             84.70n ± 0%   78.44n ± 0%   -7.40% (p=0.000 n=20)
AppendFloat/64Fixed16-8             71.68n ± 0%   65.16n ± 0%   -9.10% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-8         68.41n ± 0%   62.16n ± 0%   -9.14% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-8         79.31n ± 0%   73.92n ± 0%   -6.80% (p=0.000 n=20)
AppendFloat/64Fixed18Hard-8         4.290µ ± 0%   4.285µ ± 0%   -0.12% (p=0.000 n=20)
AppendFloat/64FixedF1-8             216.0n ± 0%   216.1n ± 0%        ~ (p=0.090 n=20)
AppendFloat/64FixedF2-8             228.2n ± 0%   227.8n ± 0%   -0.18% (p=0.000 n=20)
AppendFloat/64FixedF3-8             208.8n ± 0%   208.2n ± 0%   -0.29% (p=0.000 n=20)
AppendFloat/Slowpath64-8            98.56n ± 0%   97.42n ± 0%   -1.16% (p=0.000 n=20)
AppendFloat/SlowpathDenormal64-8    95.81n ± 0%   94.77n ± 0%   -1.09% (p=0.000 n=20)
geomean                             93.81n        87.87n        -6.33%

host: local
goos: darwin
cpu: Apple M3 Pro
                                  │ 14b7e09f493 │             f9bf7fcb8e2              │
                                  │   sec/op    │    sec/op     vs base                │
AppendFloat/Decimal-12              21.14n ± 0%   21.15n ±  0%        ~ (p=0.963 n=20)
AppendFloat/Float-12                32.48n ± 1%   32.43n ±  0%        ~ (p=0.358 n=20)
AppendFloat/Exp-12                  31.85n ± 0%   31.94n ±  1%        ~ (p=0.634 n=20)
AppendFloat/NegExp-12               31.75n ± 0%   32.04n ±  0%        ~ (p=0.004 n=20)
AppendFloat/LongExp-12              33.55n ± 0%   33.81n ±  0%   +0.77% (p=0.000 n=20)
AppendFloat/Big-12                  35.62n ± 1%   35.73n ±  1%        ~ (p=0.888 n=20)
AppendFloat/BinaryExp-12            19.26n ± 0%   19.46n ±  1%   +1.06% (p=0.000 n=20)
AppendFloat/32Integer-12            21.41n ± 0%   21.46n ±  1%        ~ (p=0.733 n=20)
AppendFloat/32ExactFraction-12      31.23n ± 1%   31.30n ±  1%        ~ (p=0.857 n=20)
AppendFloat/32Point-12              31.39n ± 1%   31.02n ±  0%   -1.19% (p=0.000 n=20)
AppendFloat/32Exp-12                32.42n ± 1%   31.52n ±  1%   -2.79% (p=0.000 n=20)
AppendFloat/32NegExp-12             30.66n ± 1%   30.66n ±  1%        ~ (p=0.380 n=20)
AppendFloat/32Shortest-12           26.88n ± 1%   27.25n ±  1%   +1.36% (p=0.000 n=20)
AppendFloat/32Fixed8Hard-12         19.52n ± 0%   17.09n ±  1%  -12.45% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-12         21.55n ± 2%   19.11n ±  1%  -11.35% (p=0.000 n=20)
AppendFloat/64Fixed1-12             18.64n ± 0%   15.49n ±  0%  -16.90% (p=0.000 n=20)
AppendFloat/64Fixed2-12             18.65n ± 0%   15.49n ±  0%  -16.97% (p=0.000 n=20)
AppendFloat/64Fixed2.5-12           19.23n ± 1%   15.24n ±  0%  -20.75% (p=0.000 n=20)
AppendFloat/64Fixed3-12             18.61n ± 0%   15.59n ±  1%  -16.21% (p=0.000 n=20)
AppendFloat/64Fixed4-12             17.55n ± 1%   15.38n ±  0%  -12.36% (p=0.000 n=20)
AppendFloat/64Fixed5Hard-12         29.27n ± 1%   17.97n ±  0%  -38.59% (p=0.000 n=20)
AppendFloat/64Fixed12-12            28.26n ± 1%   28.17n ± 10%        ~ (p=0.941 n=20)
AppendFloat/64Fixed16-12            23.56n ± 0%   21.46n ±  0%   -8.95% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-12        21.85n ± 2%   20.70n ±  1%   -5.24% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-12        26.91n ± 1%   27.10n ±  0%        ~ (p=0.059 n=20)
AppendFloat/64Fixed18Hard-12        2.197µ ± 1%   2.169µ ±  1%        ~ (p=0.013 n=20)
AppendFloat/64FixedF1-12            103.7n ± 1%   103.3n ±  0%        ~ (p=0.035 n=20)
AppendFloat/64FixedF2-12            114.8n ± 1%   114.1n ±  1%        ~ (p=0.234 n=20)
AppendFloat/64FixedF3-12            107.8n ± 1%   107.1n ±  1%        ~ (p=0.180 n=20)
AppendFloat/Slowpath64-12           32.05n ± 1%   32.00n ±  0%        ~ (p=0.952 n=20)
AppendFloat/SlowpathDenormal64-12   29.98n ± 1%   30.20n ±  0%        ~ (p=0.004 n=20)
geomean                             33.83n        31.91n         -5.68%

host: linux-amd64
goos: linux
goarch: amd64
cpu: Intel(R) Xeon(R) CPU @ 2.30GHz
                                  │ 14b7e09f493  │             f9bf7fcb8e2              │
                                  │    sec/op    │    sec/op     vs base                │
AppendFloat/Decimal-16               64.00n ± 1%    63.67n ± 1%        ~ (p=0.784 n=20)
AppendFloat/Float-16                 95.99n ± 1%    97.42n ± 1%   +1.50% (p=0.000 n=20)
AppendFloat/Exp-16                   97.59n ± 1%    97.72n ± 1%        ~ (p=0.984 n=20)
AppendFloat/NegExp-16                97.80n ± 1%   101.15n ± 1%   +3.43% (p=0.000 n=20)
AppendFloat/LongExp-16               103.1n ± 1%    104.5n ± 1%        ~ (p=0.006 n=20)
AppendFloat/Big-16                   110.8n ± 1%    108.5n ± 1%   -2.07% (p=0.000 n=20)
AppendFloat/BinaryExp-16             47.82n ± 1%    47.33n ± 1%        ~ (p=0.007 n=20)
AppendFloat/32Integer-16             63.65n ± 1%    63.51n ± 0%        ~ (p=0.560 n=20)
AppendFloat/32ExactFraction-16       91.81n ± 1%    97.03n ± 1%   +5.69% (p=0.000 n=20)
AppendFloat/32Point-16               89.84n ± 1%    92.16n ± 1%   +2.59% (p=0.000 n=20)
AppendFloat/32Exp-16                103.80n ± 1%    95.12n ± 1%   -8.36% (p=0.000 n=20)
AppendFloat/32NegExp-16              93.70n ± 1%    94.87n ± 1%        ~ (p=0.003 n=20)
AppendFloat/32Shortest-16            83.98n ± 1%    86.45n ± 1%   +2.94% (p=0.000 n=20)
AppendFloat/32Fixed8Hard-16          61.91n ± 1%    57.81n ± 1%   -6.62% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-16          71.08n ± 0%    66.81n ± 1%   -6.01% (p=0.000 n=20)
AppendFloat/64Fixed1-16              59.27n ± 2%    51.49n ± 1%  -13.13% (p=0.000 n=20)
AppendFloat/64Fixed2-16              57.89n ± 1%    50.87n ± 1%  -12.13% (p=0.000 n=20)
AppendFloat/64Fixed2.5-16            61.04n ± 1%    49.40n ± 1%  -19.08% (p=0.000 n=20)
AppendFloat/64Fixed3-16              58.42n ± 1%    52.14n ± 1%  -10.75% (p=0.000 n=20)
AppendFloat/64Fixed4-16              56.52n ± 1%    50.27n ± 1%  -11.07% (p=0.000 n=20)
AppendFloat/64Fixed5Hard-16          97.79n ± 1%    57.86n ± 1%  -40.83% (p=0.000 n=20)
AppendFloat/64Fixed12-16             90.78n ± 1%    83.01n ± 1%   -8.56% (p=0.000 n=20)
AppendFloat/64Fixed16-16             76.11n ± 1%    70.84n ± 0%   -6.92% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-16         73.56n ± 1%    68.98n ± 2%   -6.23% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-16         83.20n ± 1%    79.85n ± 1%   -4.03% (p=0.000 n=20)
AppendFloat/64Fixed18Hard-16         4.947µ ± 1%    4.915µ ± 1%        ~ (p=0.229 n=20)
AppendFloat/64FixedF1-16             242.4n ± 1%    239.4n ± 1%        ~ (p=0.038 n=20)
AppendFloat/64FixedF2-16             257.7n ± 2%    252.6n ± 1%   -1.98% (p=0.000 n=20)
AppendFloat/64FixedF3-16             237.5n ± 0%    237.5n ± 1%        ~ (p=0.440 n=20)
AppendFloat/Slowpath64-16            99.75n ± 1%    99.78n ± 1%        ~ (p=0.995 n=20)
AppendFloat/SlowpathDenormal64-16    97.41n ± 1%    98.20n ± 1%        ~ (p=0.006 n=20)
geomean                              100.7n         95.60n        -5.05%

host: s7
cpu: AMD Ryzen 9 7950X 16-Core Processor
                                  │ 14b7e09f493 │             f9bf7fcb8e2             │
                                  │   sec/op    │   sec/op     vs base                │
AppendFloat/Decimal-32              22.19n ± 0%   22.04n ± 0%   -0.68% (p=0.000 n=20)
AppendFloat/Float-32                34.59n ± 0%   34.88n ± 0%   +0.84% (p=0.000 n=20)
AppendFloat/Exp-32                  34.47n ± 0%   34.88n ± 0%   +1.20% (p=0.000 n=20)
AppendFloat/NegExp-32               34.85n ± 0%   35.32n ± 0%   +1.35% (p=0.000 n=20)
AppendFloat/LongExp-32              37.23n ± 0%   37.09n ± 0%        ~ (p=0.003 n=20)
AppendFloat/Big-32                  39.27n ± 0%   38.50n ± 0%   -1.97% (p=0.000 n=20)
AppendFloat/BinaryExp-32            17.38n ± 0%   17.61n ± 0%   +1.35% (p=0.000 n=20)
AppendFloat/32Integer-32            22.26n ± 0%   22.08n ± 0%   -0.79% (p=0.000 n=20)
AppendFloat/32ExactFraction-32      32.82n ± 0%   32.91n ± 0%        ~ (p=0.018 n=20)
AppendFloat/32Point-32              32.88n ± 0%   33.22n ± 0%   +1.03% (p=0.000 n=20)
AppendFloat/32Exp-32                34.95n ± 0%   34.62n ± 0%   -0.94% (p=0.000 n=20)
AppendFloat/32NegExp-32             33.23n ± 0%   33.55n ± 0%   +0.98% (p=0.000 n=20)
AppendFloat/32Shortest-32           30.19n ± 0%   30.12n ± 0%        ~ (p=0.122 n=20)
AppendFloat/32Fixed8Hard-32         22.94n ± 0%   22.88n ± 0%        ~ (p=0.124 n=20)
AppendFloat/32Fixed9Hard-32         26.20n ± 0%   25.94n ± 1%   -0.97% (p=0.000 n=20)
AppendFloat/64Fixed1-32             21.10n ± 0%   18.84n ± 0%  -10.71% (p=0.000 n=20)
AppendFloat/64Fixed2-32             20.75n ± 0%   18.70n ± 0%   -9.88% (p=0.000 n=20)
AppendFloat/64Fixed2.5-32           21.07n ± 0%   17.96n ± 0%  -14.74% (p=0.000 n=20)
AppendFloat/64Fixed3-32             21.24n ± 0%   19.64n ± 0%   -7.53% (p=0.000 n=20)
AppendFloat/64Fixed4-32             20.63n ± 0%   18.61n ± 0%   -9.79% (p=0.000 n=20)
AppendFloat/64Fixed5Hard-32         34.48n ± 0%   21.70n ± 0%  -37.06% (p=0.000 n=20)
AppendFloat/64Fixed12-32            32.26n ± 0%   30.87n ± 1%   -4.31% (p=0.000 n=20)
AppendFloat/64Fixed16-32            27.95n ± 0%   26.86n ± 0%   -3.92% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-32        27.30n ± 0%   25.98n ± 1%   -4.82% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-32        30.80n ± 0%   29.93n ± 0%   -2.84% (p=0.000 n=20)
AppendFloat/64Fixed18Hard-32        1.833µ ± 0%   1.831µ ± 0%        ~ (p=0.663 n=20)
AppendFloat/64FixedF1-32            83.42n ± 1%   84.00n ± 1%        ~ (p=0.003 n=20)
AppendFloat/64FixedF2-32            90.10n ± 0%   89.23n ± 1%   -0.95% (p=0.001 n=20)
AppendFloat/64FixedF3-32            84.42n ± 1%   84.39n ± 0%        ~ (p=0.878 n=20)
AppendFloat/Slowpath64-32           35.72n ± 0%   35.59n ± 0%        ~ (p=0.007 n=20)
AppendFloat/SlowpathDenormal64-32   35.36n ± 0%   35.05n ± 0%   -0.88% (p=0.000 n=20)
geomean                             36.05n        34.69n        -3.77%

host: linux-386
goarch: 386
cpu: Intel(R) Xeon(R) CPU @ 2.30GHz
                                  │ 14b7e09f493 │             f9bf7fcb8e2             │
                                  │   sec/op    │   sec/op     vs base                │
AppendFloat/Decimal-16              132.8n ± 0%   133.5n ± 0%   +0.49% (p=0.001 n=20)
AppendFloat/Float-16                242.6n ± 0%   241.7n ± 0%   -0.37% (p=0.000 n=20)
AppendFloat/Exp-16                  252.2n ± 0%   249.1n ± 0%   -1.27% (p=0.000 n=20)
AppendFloat/NegExp-16               253.6n ± 0%   247.7n ± 0%   -2.33% (p=0.000 n=20)
AppendFloat/LongExp-16              260.9n ± 0%   257.1n ± 0%   -1.48% (p=0.000 n=20)
AppendFloat/Big-16                  293.7n ± 0%   285.2n ± 0%   -2.89% (p=0.000 n=20)
AppendFloat/BinaryExp-16            89.63n ± 1%   89.06n ± 0%   -0.64% (p=0.000 n=20)
AppendFloat/32Integer-16            132.6n ± 0%   133.2n ± 0%        ~ (p=0.016 n=20)
AppendFloat/32ExactFraction-16      216.9n ± 0%   214.2n ± 0%   -1.24% (p=0.000 n=20)
AppendFloat/32Point-16              205.0n ± 0%   202.2n ± 0%   -1.37% (p=0.000 n=20)
AppendFloat/32Exp-16                250.2n ± 0%   235.9n ± 0%   -5.72% (p=0.000 n=20)
AppendFloat/32NegExp-16             213.5n ± 0%   210.6n ± 0%   -1.34% (p=0.000 n=20)
AppendFloat/32Shortest-16           198.3n ± 0%   197.8n ± 0%        ~ (p=0.147 n=20)
AppendFloat/32Fixed8Hard-16         114.9n ± 1%   136.0n ± 1%  +18.46% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-16         189.8n ± 0%   155.0n ± 1%  -18.31% (p=0.000 n=20)
AppendFloat/64Fixed1-16             175.8n ± 0%   132.7n ± 0%  -24.52% (p=0.000 n=20)
AppendFloat/64Fixed2-16             166.6n ± 0%   128.7n ± 0%  -22.73% (p=0.000 n=20)
AppendFloat/64Fixed2.5-16           176.5n ± 0%   126.8n ± 0%  -28.11% (p=0.000 n=20)
AppendFloat/64Fixed3-16             165.3n ± 0%   127.1n ± 0%  -23.11% (p=0.000 n=20)
AppendFloat/64Fixed4-16             141.3n ± 0%   120.8n ± 1%  -14.51% (p=0.000 n=20)
AppendFloat/64Fixed5Hard-16         344.6n ± 0%   136.0n ± 0%  -60.51% (p=0.000 n=20)
AppendFloat/64Fixed12-16            184.2n ± 0%   158.7n ± 0%  -13.82% (p=0.000 n=20)
AppendFloat/64Fixed16-16            174.0n ± 0%   151.3n ± 0%  -12.99% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-16        169.7n ± 0%   146.7n ± 0%  -13.58% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-16        207.7n ± 0%   166.6n ± 0%  -19.81% (p=0.000 n=20)
AppendFloat/64Fixed18Hard-16        10.66µ ± 0%   10.63µ ± 0%        ~ (p=0.030 n=20)
AppendFloat/64FixedF1-16            615.9n ± 0%   613.5n ± 0%   -0.40% (p=0.000 n=20)
AppendFloat/64FixedF2-16            846.6n ± 0%   847.4n ± 0%        ~ (p=0.551 n=20)
AppendFloat/64FixedF3-16            609.9n ± 0%   609.5n ± 0%        ~ (p=0.213 n=20)
AppendFloat/Slowpath64-16           254.1n ± 0%   252.6n ± 1%        ~ (p=0.048 n=20)
AppendFloat/SlowpathDenormal64-16   251.5n ± 0%   249.4n ± 0%   -0.83% (p=0.000 n=20)
geomean                             249.2n        225.4n        -9.54%

host: s7:GOARCH=386
cpu: AMD Ryzen 9 7950X 16-Core Processor
                                  │ 14b7e09f493 │             f9bf7fcb8e2             │
                                  │   sec/op    │   sec/op     vs base                │
AppendFloat/Decimal-32              42.65n ± 0%   42.31n ± 0%   -0.79% (p=0.000 n=20)
AppendFloat/Float-32                71.56n ± 0%   71.06n ± 0%   -0.69% (p=0.000 n=20)
AppendFloat/Exp-32                  75.61n ± 1%   74.85n ± 1%   -1.01% (p=0.000 n=20)
AppendFloat/NegExp-32               74.36n ± 0%   74.30n ± 0%        ~ (p=0.482 n=20)
AppendFloat/LongExp-32              75.82n ± 0%   75.73n ± 0%        ~ (p=0.490 n=20)
AppendFloat/Big-32                  85.10n ± 0%   82.61n ± 0%   -2.93% (p=0.000 n=20)
AppendFloat/BinaryExp-32            33.02n ± 0%   32.48n ± 1%   -1.64% (p=0.000 n=20)
AppendFloat/32Integer-32            41.54n ± 1%   41.27n ± 1%   -0.66% (p=0.000 n=20)
AppendFloat/32ExactFraction-32      62.48n ± 0%   62.91n ± 0%   +0.69% (p=0.000 n=20)
AppendFloat/32Point-32              60.17n ± 0%   60.65n ± 0%   +0.80% (p=0.000 n=20)
AppendFloat/32Exp-32                73.34n ± 0%   68.99n ± 0%   -5.92% (p=0.000 n=20)
AppendFloat/32NegExp-32             63.29n ± 0%   62.83n ± 0%   -0.73% (p=0.000 n=20)
AppendFloat/32Shortest-32           58.97n ± 0%   59.07n ± 0%        ~ (p=0.029 n=20)
AppendFloat/32Fixed8Hard-32         37.42n ± 0%   41.76n ± 1%  +11.61% (p=0.000 n=20)
AppendFloat/32Fixed9Hard-32         55.18n ± 0%   50.13n ± 1%   -9.16% (p=0.000 n=20)
AppendFloat/64Fixed1-32             50.89n ± 1%   41.25n ± 0%  -18.94% (p=0.000 n=20)
AppendFloat/64Fixed2-32             48.33n ± 1%   40.85n ± 1%  -15.48% (p=0.000 n=20)
AppendFloat/64Fixed2.5-32           52.46n ± 0%   39.39n ± 0%  -24.92% (p=0.000 n=20)
AppendFloat/64Fixed3-32             48.28n ± 1%   40.66n ± 0%  -15.78% (p=0.000 n=20)
AppendFloat/64Fixed4-32             44.57n ± 0%   38.58n ± 0%  -13.44% (p=0.000 n=20)
AppendFloat/64Fixed5Hard-32         96.16n ± 0%   42.99n ± 1%  -55.29% (p=0.000 n=20)
AppendFloat/64Fixed12-32            56.84n ± 0%   51.95n ± 1%   -8.61% (p=0.000 n=20)
AppendFloat/64Fixed16-32            54.23n ± 0%   49.33n ± 0%   -9.03% (p=0.000 n=20)
AppendFloat/64Fixed12Hard-32        53.47n ± 0%   48.67n ± 0%   -8.99% (p=0.000 n=20)
AppendFloat/64Fixed17Hard-32        61.76n ± 0%   55.42n ± 1%  -10.27% (p=0.000 n=20)
AppendFloat/64Fixed18Hard-32        3.998µ ± 1%   4.001µ ± 0%        ~ (p=0.449 n=20)
AppendFloat/64FixedF1-32            161.8n ± 0%   166.2n ± 1%   +2.72% (p=0.000 n=20)
AppendFloat/64FixedF2-32            223.4n ± 2%   226.2n ± 1%   +1.25% (p=0.000 n=20)
AppendFloat/64FixedF3-32            159.6n ± 0%   161.6n ± 1%   +1.22% (p=0.000 n=20)
AppendFloat/Slowpath64-32           76.69n ± 0%   75.03n ± 0%   -2.16% (p=0.000 n=20)
AppendFloat/SlowpathDenormal64-32   75.02n ± 0%   74.36n ± 1%        ~ (p=0.003 n=20)
geomean                             74.66n        69.39n        -7.06%

Change-Id: I9db46471a93bd2aab3c2796e563d154cb531d4cb

Reviewed-on: https://go-review.googlesource.com/c/go/+/717182

Reviewed-by: Alan Donovan <adon...@google.com>

LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Auto-Submit: Russ Cox <r...@golang.org>

Files:

M src/internal/strconv/atoi.go
M src/internal/strconv/export_test.go
M src/internal/strconv/ftoa.go
M src/internal/strconv/ftoa_test.go
A src/internal/strconv/ftoafixed.go
M src/internal/strconv/ftoaryu.go
M src/internal/strconv/import_test.go
M src/internal/strconv/math.go
M src/internal/strconv/math_test.go

Change size: L

Delta: 9 files changed, 383 insertions(+), 228 deletions(-)

Branch: refs/heads/master

Submit Requirements:

Code-Review: +2 by Alan Donovan
TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI

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[go] internal/strconv: extract fixed-precision ftoa from ftoaryu.go

Russ Cox (Gerrit)

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