strconv: make Ftoa faster
Make code amenable to escape analysis
so that the decimal values do not escape.
benchmark old ns/op new ns/op delta
strconv_test.BenchmarkAtof64Decimal 229 233 +1.75%
strconv_test.BenchmarkAtof64Float 261 263 +0.77%
strconv_test.BenchmarkAtof64FloatExp 7760 7757 -0.04%
strconv_test.BenchmarkAtof64Big 3086 3053 -1.07%
strconv_test.BenchmarkFtoa64Decimal 6866 2629 -61.71%
strconv_test.BenchmarkFtoa64Float 7211 3064 -57.51%
strconv_test.BenchmarkFtoa64FloatExp 12587 8263 -34.35%
strconv_test.BenchmarkFtoa64Big 7058 2825 -59.97%
json.BenchmarkCodeEncoder 357355200 276528200 -22.62%
json.BenchmarkCodeMarshal 360735200 279646400 -22.48%
json.BenchmarkCodeDecoder 731528600 709460600 -3.02%
json.BenchmarkCodeUnmarshal 754774400 731051200 -3.14%
json.BenchmarkCodeUnmarshalReuse 713379000 704218000 -1.28%
json.BenchmarkSkipValue 51594300 51682600 +0.17%
benchmark old MB/s new MB/s speedup
json.BenchmarkCodeEncoder 5.43 7.02 1.29x
json.BenchmarkCodeMarshal 5.38 6.94 1.29x
json.BenchmarkCodeDecoder 2.65 2.74 1.03x
json.BenchmarkCodeUnmarshal 2.57 2.65 1.03x
json.BenchmarkCodeUnmarshalReuse 2.72 2.76 1.01x
json.BenchmarkSkipValue 38.61 38.55 1.00x
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5369111
diff --git a/src/pkg/strconv/ftoa.go b/src/pkg/strconv/ftoa.go
index 07fe806..8342b6a 100644
--- a/src/pkg/strconv/ftoa.go
+++ b/src/pkg/strconv/ftoa.go
@@ -98,7 +98,8 @@
// The shift is exp - flt.mantbits because mant is a 1-bit integer
// followed by a flt.mantbits fraction, and we are treating it as
// a 1+flt.mantbits-bit integer.
- d := newDecimal(mant)
+ d := new(decimal)
+ d.Assign(mant)
d.Shift(exp - int(flt.mantbits))
// Round appropriately.
@@ -184,7 +185,8 @@
// d = mant << (exp - mantbits)
// Next highest floating point number is mant+1 << exp-mantbits.
// Our upper bound is halfway inbetween, mant*2+1 << exp-mantbits-1.
- upper := newDecimal(mant*2 + 1)
+ upper := new(decimal)
+ upper.Assign(mant*2 + 1)
upper.Shift(exp - int(flt.mantbits) - 1)
// d = mant << (exp - mantbits)
@@ -203,7 +205,8 @@
mantlo = mant*2 - 1
explo = exp - 1
}
- lower := newDecimal(mantlo*2 + 1)
+ lower := new(decimal)
+ lower.Assign(mantlo*2 + 1)
lower.Shift(explo - int(flt.mantbits) - 1)
// The upper and lower bounds are possible outputs only if
