snappy comparison with upstream need updating

[nigeltao]

You are obviously free to respond however you want, but FYI the upstream github.com/golang/snappy encoder now implements an asm version of what you call matchLenSSE4, and it (call this "new") now compares favorably with the github.com/klauspost/compress/snappy version (call this "old"):

benchmark                     old MB/s     new MB/s     speedup
BenchmarkWordsEncode1e1-8     153.77       673.38       4.38x
BenchmarkWordsEncode1e2-8     217.81       428.78       1.97x
BenchmarkWordsEncode1e3-8     282.31       446.89       1.58x
BenchmarkWordsEncode1e4-8     225.73       315.17       1.40x
BenchmarkWordsEncode1e5-8     158.92       267.72       1.68x
BenchmarkWordsEncode1e6-8     206.50       311.30       1.51x
BenchmarkRandomEncode-8       4055.50      14507.66     3.58x
Benchmark_ZFlat0-8            481.82       791.69       1.64x
Benchmark_ZFlat1-8            190.36       434.39       2.28x
Benchmark_ZFlat2-8            6436.37      16301.77     2.53x
Benchmark_ZFlat3-8            368.55       632.13       1.72x
Benchmark_ZFlat4-8            3257.82      7990.39      2.45x
Benchmark_ZFlat5-8            474.40       764.96       1.61x
Benchmark_ZFlat6-8            183.83       280.09       1.52x
Benchmark_ZFlat7-8            170.28       262.54       1.54x
Benchmark_ZFlat8-8            190.70       298.19       1.56x
Benchmark_ZFlat9-8            158.43       247.14       1.56x
Benchmark_ZFlat10-8           581.40       1028.24      1.77x
Benchmark_ZFlat11-8           310.57       408.89       1.32x

For the record, here's the -tags=noasm comparison. The numbers are worse for small inputs but better for large inputs, which I'd argue is still a net improvement:

benchmark                     old MB/s     new MB/s     speedup
BenchmarkWordsEncode1e1-8     140.02       677.54       4.84x
BenchmarkWordsEncode1e2-8     224.74       86.86        0.39x
BenchmarkWordsEncode1e3-8     274.82       258.34       0.94x
BenchmarkWordsEncode1e4-8     189.95       244.60       1.29x
BenchmarkWordsEncode1e5-8     140.10       185.91       1.33x
BenchmarkWordsEncode1e6-8     169.03       211.16       1.25x
BenchmarkRandomEncode-8       3746.11      13192.30     3.52x
Benchmark_ZFlat0-8            357.12       430.88       1.21x
Benchmark_ZFlat1-8            181.27       276.50       1.53x
Benchmark_ZFlat2-8            5959.15      14075.70     2.36x
Benchmark_ZFlat3-8            312.09       171.85       0.55x
Benchmark_ZFlat4-8            2008.62      3111.51      1.55x
Benchmark_ZFlat5-8            357.46       425.45       1.19x
Benchmark_ZFlat6-8            155.59       189.98       1.22x
Benchmark_ZFlat7-8            149.70       182.01       1.22x
Benchmark_ZFlat8-8            160.04       199.81       1.25x
Benchmark_ZFlat9-8            140.87       175.73       1.25x
Benchmark_ZFlat10-8           415.88       509.88       1.23x
Benchmark_ZFlat11-8           236.50       274.77       1.16x

In any case, the regular case (without -tags=noasm) seems always faster with upstream snappy, on this limited set of benchmarks.

[klauspost]

Snappy replaced wit upstream.