strconv: Speed improvement to number parsing
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 #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>
diff --git a/src/strconv/atof.go b/src/strconv/atof.go
index 190b25f..23de70b 100644
--- a/src/strconv/atof.go
+++ b/src/strconv/atof.go
@@ -84,7 +84,7 @@
for ; i < len(s); i++ {
switch {
case s[i] == '_':
- // underscoreOK already called
+ // readFloat already checked underscores
continue
case s[i] == '.':
if sawdot {
@@ -140,7 +140,7 @@
e := 0
for ; i < len(s) && ('0' <= s[i] && s[i] <= '9' || s[i] == '_'); i++ {
if s[i] == '_' {
- // underscoreOK already called
+ // readFloat already checked underscores
continue
}
if e < 10000 {
@@ -159,10 +159,11 @@
}
// readFloat reads a decimal mantissa and exponent from a float
-// string representation. It returns ok==false if the number could
-// not fit return types or is invalid.
+// string representation. It returns ok==false if the number
+// is invalid.
func readFloat(s string) (mantissa uint64, exp int, neg, trunc, hex, ok bool) {
i := 0
+ underscores := false
// optional sign
if i >= len(s) {
@@ -195,7 +196,7 @@
for ; i < len(s); i++ {
switch c := s[i]; true {
case c == '_':
- // underscoreOK already called
+ underscores = true
continue
case c == '.':
@@ -271,7 +272,7 @@
e := 0
for ; i < len(s) && ('0' <= s[i] && s[i] <= '9' || s[i] == '_'); i++ {
if s[i] == '_' {
- // underscoreOK already called
+ underscores = true
continue
}
if e < 10000 {
@@ -291,6 +292,11 @@
if mantissa != 0 {
exp = dp - ndMant
}
+
+ if underscores && !underscoreOK(s) {
+ return
+ }
+
ok = true
return
}
@@ -554,12 +560,16 @@
}
mantissa, exp, neg, trunc, hex, ok := readFloat(s)
- if hex && ok {
+ if !ok {
+ return 0, syntaxError(fnParseFloat, s)
+ }
+
+ if hex {
f, err := atofHex(s, &float32info, mantissa, exp, neg, trunc)
return float32(f), err
}
- if optimize && ok {
+ if optimize {
// Try pure floating-point arithmetic conversion.
if !trunc {
if f, ok := atof32exact(mantissa, exp, neg); ok {
@@ -597,11 +607,15 @@
}
mantissa, exp, neg, trunc, hex, ok := readFloat(s)
- if hex && ok {
+ if !ok {
+ return 0, syntaxError(fnParseFloat, s)
+ }
+
+ if hex {
return atofHex(s, &float64info, mantissa, exp, neg, trunc)
}
- if optimize && ok {
+ if optimize {
// Try pure floating-point arithmetic conversion.
if !trunc {
if f, ok := atof64exact(mantissa, exp, neg); ok {
@@ -658,9 +672,6 @@
// ParseFloat recognizes the strings "NaN", "+Inf", and "-Inf" as their
// respective special floating point values. It ignores case when matching.
func ParseFloat(s string, bitSize int) (float64, error) {
- if !underscoreOK(s) {
- return 0, syntaxError(fnParseFloat, s)
- }
if bitSize == 32 {
f, err := atof32(s)
return float64(f), err
diff --git a/src/strconv/atoi.go b/src/strconv/atoi.go
index e811bc4..131b088 100644
--- a/src/strconv/atoi.go
+++ b/src/strconv/atoi.go
@@ -58,7 +58,7 @@
func ParseUint(s string, base int, bitSize int) (uint64, error) {
const fnParseUint = "ParseUint"
- if s == "" || !underscoreOK(s) {
+ if s == "" {
return 0, syntaxError(fnParseUint, s)
}
@@ -113,12 +113,13 @@
maxVal := uint64(1)<<uint(bitSize) - 1
+ underscores := false
var n uint64
for _, c := range []byte(s) {
var d byte
switch {
case c == '_' && base0:
- // underscoreOK already called
+ underscores = true
continue
case '0' <= c && c <= '9':
d = c - '0'
@@ -146,6 +147,10 @@
n = n1
}
+ if underscores && !underscoreOK(s0) {
+ return 0, syntaxError(fnParseUint, s0)
+ }
+
return n, nil
}
