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encoding/gob: speedup floats encoding and decoding

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By replacing bytes-reversing routines with bits.ReverseBytes64 calls.

name                     old time/op  new time/op  delta
EncodeComplex128Slice-4  35.1µs ± 1%  23.2µs ± 2%  -33.94%  (p=0.000 n=20+20)
EncodeFloat64Slice-4     17.9µs ± 1%  11.0µs ± 1%  -38.36%  (p=0.000 n=17+18)

name                     old time/op  new time/op  delta
DecodeComplex128Slice-4  79.7µs ± 0%  69.9µs ± 1%  -12.31%  (p=0.000 n=20+20)
DecodeFloat64Slice-4     47.3µs ± 1%  42.2µs ± 1%  -10.65%  (p=0.000 n=17+17)

Change-Id: I91a6401c6009b5712fca6258dd1e57c6fe68ea64
Reviewed-on: https://go-review.googlesource.com/38352
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Alberto Donizetti 2017-03-18 18:43:20 +01:00 • committed by Brad Fitzpatrick
parent b6074a417d
commit 32cb0ce65b
2 changed files with 3 additions and 13 deletions
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8
src/encoding/gob/encode.go
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@ -209,13 +209,7 @@ func encUint(i *encInstr, state *encoderState, v reflect.Value) {
// swizzling.
func floatBits(f float64) uint64 {
u := math.Float64bits(f)
var v uint64
for i := 0; i < 8; i++ {
v <<= 8
v |= u & 0xFF
u >>= 8
}
return v
return bits.ReverseBytes64(u)
}
// encFloat encodes the floating point value (float32 float64) referenced by v.