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/decimal.go b/src/pkg/strconv/decimal.go
index f572ea4..5415530 100644
--- a/src/pkg/strconv/decimal.go
+++ b/src/pkg/strconv/decimal.go
@@ -102,12 +102,6 @@
trim(a)
}
-func newDecimal(i uint64) *decimal {
- a := new(decimal)
- a.Assign(i)
- return a
-}
-
// Maximum shift that we can do in one pass without overflow.
// Signed int has 31 bits, and we have to be able to accommodate 9<<k.
const maxShift = 27
@@ -303,32 +297,32 @@
// If nd is zero, it means we're rounding
// just to the left of the digits, as in
// 0.09 -> 0.1.
-func (a *decimal) Round(nd int) *decimal {
+func (a *decimal) Round(nd int) {
if nd < 0 || nd >= a.nd {
- return a
+ return
}
if shouldRoundUp(a, nd) {
- return a.RoundUp(nd)
+ a.RoundUp(nd)
+ } else {
+ a.RoundDown(nd)
}
- return a.RoundDown(nd)
}
// Round a down to nd digits (or fewer).
// Returns receiver for convenience.
-func (a *decimal) RoundDown(nd int) *decimal {
+func (a *decimal) RoundDown(nd int) {
if nd < 0 || nd >= a.nd {
- return a
+ return
}
a.nd = nd
trim(a)
- return a
}
// Round a up to nd digits (or fewer).
// Returns receiver for convenience.
-func (a *decimal) RoundUp(nd int) *decimal {
+func (a *decimal) RoundUp(nd int) {
if nd < 0 || nd >= a.nd {
- return a
+ return
}
// round up
@@ -337,7 +331,7 @@
if c < '9' { // can stop after this digit
a.d[i]++
a.nd = i + 1
- return a
+ return
}
}
@@ -346,7 +340,6 @@
a.d[0] = '1'
a.nd = 1
a.dp++
- return a
}
// Extract integer part, rounded appropriately.
diff --git a/src/pkg/strconv/decimal_test.go b/src/pkg/strconv/decimal_test.go
index deb2e02..13a127f 100644
--- a/src/pkg/strconv/decimal_test.go
+++ b/src/pkg/strconv/decimal_test.go
@@ -70,17 +70,23 @@
func TestDecimalRound(t *testing.T) {
for i := 0; i < len(roundtests); i++ {
test := &roundtests[i]
- s := NewDecimal(test.i).RoundDown(test.nd).String()
+ d := NewDecimal(test.i)
+ d.RoundDown(test.nd)
+ s := d.String()
if s != test.down {
t.Errorf("Decimal %v RoundDown %d = %v, want %v",
test.i, test.nd, s, test.down)
}
- s = NewDecimal(test.i).Round(test.nd).String()
+ d = NewDecimal(test.i)
+ d.Round(test.nd)
+ s = d.String()
if s != test.round {
t.Errorf("Decimal %v Round %d = %v, want %v",
test.i, test.nd, s, test.down)
}
- s = NewDecimal(test.i).RoundUp(test.nd).String()
+ d = NewDecimal(test.i)
+ d.RoundUp(test.nd)
+ s = d.String()
if s != test.up {
t.Errorf("Decimal %v RoundUp %d = %v, want %v",
test.i, test.nd, s, test.up)
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
diff --git a/src/pkg/strconv/internal_test.go b/src/pkg/strconv/internal_test.go
index 9a7f4f0..d0fa80e 100644
--- a/src/pkg/strconv/internal_test.go
+++ b/src/pkg/strconv/internal_test.go
@@ -6,7 +6,11 @@
package strconv
-func NewDecimal(i uint64) *decimal { return newDecimal(i) }
+func NewDecimal(i uint64) *decimal {
+ d := new(decimal)
+ d.Assign(i)
+ return d
+}
func SetOptimize(b bool) bool {
old := optimize
