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fmt: speed up 10-20%

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The check for Stringer etc. can only fire if the test is not a builtin, so avoid
the expensive check if we know there's no chance.
Also put in a fast path for pad, which saves a more modest amount.

benchmark                      old ns/op    new ns/op    delta
BenchmarkSprintfEmpty                148          152   +2.70%
BenchmarkSprintfString               585          497  -15.04%
BenchmarkSprintfInt                  441          396  -10.20%
BenchmarkSprintfIntInt               718          603  -16.02%
BenchmarkSprintfPrefixedInt          676          621   -8.14%
BenchmarkSprintfFloat               1003          953   -4.99%
BenchmarkManyArgs                   2945         2312  -21.49%
BenchmarkScanInts                1704152      1734441   +1.78%
BenchmarkScanRecursiveInt        1837397      1828920   -0.46%

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6245068
This commit is contained in:
Rob Pike 2012-05-29 15:08:08 -07:00
parent d61707f490
commit 53bc19442d
3 changed files with 20 additions and 12 deletions
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8
src/pkg/fmt/fmt_test.go
View File

@ -527,6 +527,14 @@ func BenchmarkSprintfFloat(b *testing.B) {
}
}
func BenchmarkManyArgs(b *testing.B) {
var buf bytes.Buffer
for i := 0; i < b.N; i++ {
buf.Reset()
Fprintf(&buf, "%2d/%2d/%2d %d:%d:%d %s %s\n", 3, 4, 5, 11, 12, 13, "hello", "world")
}
}
var mallocBuf bytes.Buffer
var mallocTest = []struct {

16
src/pkg/fmt/format.go
View File

@ -110,11 +110,11 @@ func (f *fmt) writePadding(n int, padding []byte) {
// Append b to f.buf, padded on left (w > 0) or right (w < 0 or f.minus)
// clear flags afterwards.
func (f *fmt) pad(b []byte) {
var padding []byte
var left, right int
if f.widPresent && f.wid != 0 {
padding, left, right = f.computePadding(len(b))
if !f.widPresent || f.wid == 0 {
f.buf.Write(b)
return
}
padding, left, right := f.computePadding(len(b))
if left > 0 {
f.writePadding(left, padding)
}
@ -127,11 +127,11 @@ func (f *fmt) pad(b []byte) {
// append s to buf, padded on left (w > 0) or right (w < 0 or f.minus).
// clear flags afterwards.
func (f *fmt) padString(s string) {
var padding []byte
var left, right int
if f.widPresent && f.wid != 0 {
padding, left, right = f.computePadding(utf8.RuneCountInString(s))
if !f.widPresent || f.wid == 0 {
f.buf.WriteString(s)
return
}
padding, left, right := f.computePadding(utf8.RuneCountInString(s))
if left > 0 {
f.writePadding(left, padding)
}

8
src/pkg/fmt/print.go
View File

@ -734,10 +734,6 @@ func (p *pp) printField(field interface{}, verb rune, plus, goSyntax bool, depth
return false
}
if wasString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
return wasString
}
// Some types can be done without reflection.
switch f := field.(type) {
case bool:
@ -779,6 +775,10 @@ func (p *pp) printField(field interface{}, verb rune, plus, goSyntax bool, depth
p.fmtBytes(f, verb, goSyntax, depth)
wasString = verb == 's'
default:
// If the type is not simple, it might have methods.
if wasString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
return wasString
}
// Need to use reflection
return p.printReflectValue(reflect.ValueOf(field), verb, plus, goSyntax, depth)
}