png: speed up opaque RGBA encoding
With Linux/8g on a 2006 Mac Mini (1.66 GHz Intel Core Duo,
2KB L1, 2MB L2, 2G main memory), GOMAXPROCS unset:
start:
png.BenchmarkEncodePaletted 50
44772820 ns/op
png.BenchmarkEncodeRGBOpaque 10
208395900 ns/op
png.BenchmarkEncodeRGBA 5
331088000 ns/op
remove interface method calls:
png.BenchmarkEncodePaletted 50
44722880 ns/op
png.BenchmarkEncodeRGBOpaque 10
139042600 ns/op
png.BenchmarkEncodeRGBA 5
334033600 ns/op
flate inline min/max():
png.BenchmarkEncodePaletted 50
40631180 ns/op
png.BenchmarkEncodeRGBOpaque 10
124894900 ns/op
png.BenchmarkEncodeRGBA 5
312099000 ns/op
after adler change:
png.BenchmarkEncodePaletted 50
40181760 ns/op
png.BenchmarkEncodeRGBOpaque 20
121781950 ns/op
png.BenchmarkEncodeRGBA 5
313890800 ns/op
In comparison to 121 ms on this 2006 machine, on my
Core2 Duo 2.66 GHz laptop, the final BenchmarkEncodeRGBOpaque
runs in 27 ms. (these are all for 640x480 images)
R=nigeltao, rsc, r
CC=golang-dev
https://golang.org/cl/
4432077