• Nigel Tao's avatar
    hash/adler32: optimize. · 60ffae25
    Nigel Tao authored
    The bulk of the gains come from hoisting the modulo ops outside of
    the inner loop.
    
    Reducing the digest type from 8 bytes to 4 bytes gains another 1% on
    the hash/adler32 micro-benchmark.
    
    Benchmarks for $GOOS,$GOARCH = linux,amd64 below.
    
    hash/adler32 benchmark:
    benchmark             old ns/op    new ns/op    delta
    BenchmarkAdler32KB         1660         1364  -17.83%
    
    image/png benchmark:
    benchmark                       old ns/op    new ns/op    delta
    BenchmarkDecodeGray               2466909      2425539   -1.68%
    BenchmarkDecodeNRGBAGradient      9884500      9751705   -1.34%
    BenchmarkDecodeNRGBAOpaque        8511615      8379800   -1.55%
    BenchmarkDecodePaletted           1366683      1330677   -2.63%
    BenchmarkDecodeRGB                6987496      6884974   -1.47%
    BenchmarkEncodePaletted           6292408      6040052   -4.01%
    BenchmarkEncodeRGBOpaque         19780680     19178440   -3.04%
    BenchmarkEncodeRGBA              80738600     79076800   -2.06%
    
    Wall time for Denis Cheremisov's PNG-decoding program given in
    https://groups.google.com/group/golang-nuts/browse_thread/thread/22aa8a05040fdd49
    Before: 2.44s
    After:  2.26s
    Delta:  -7%
    
    R=rsc
    CC=golang-dev
    https://golang.org/cl/6251044
    60ffae25
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