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murmur3

Native Go implementation of Austin Appleby's third MurmurHash revision (aka MurmurHash3).

Includes assembly for amd64 for 64/128 bit hashes, seeding functions, and string functions to avoid string to slice conversions.

Hand rolled 32 bit assembly was removed during 1.11, but may be reintroduced if the compiler slows down any more. As is, the compiler generates marginally slower code (by one instruction in the hot loop).

The reference algorithm has been slightly hacked as to support the streaming mode required by Go's standard Hash interface.

Endianness

Unlike the canonical source, this library always reads bytes as little endian numbers. This makes the hashes portable across architectures, although does mean that hashing is a bit slower on big endian architectures.

Safety

This library used to use unsafe to convert four bytes to a uint32 and eight bytes to a uint64, but Go 1.14 introduced checks around those types of conversions that flagged that code as erroneous when hashing on unaligned input. While the code would not be problematic on amd64, it could be problematic on some architectures.

As of Go 1.14, those conversions were removed at the expense of a very minor performance hit. This hit affects all cpu architectures on for Sum32, and non-amd64 architectures for Sum64 and Sum128. For 64 and 128, custom assembly exists for amd64 that preserves performance.

Testing

Testing includes comparing random inputs against the canonical implementation, and testing length 0 through 17 inputs to force all branches.

Because this code always reads input as little endian, testing against the canonical source is skipped for big endian architectures. The canonical source just converts bytes to numbers, meaning on big endian architectures, it will use different numbers for its hashing.

Documentation

Full documentation can be found on godoc.

Benchmarks

Benchmarks below were run on an amd64 machine with and without the custom assembly. The following numbers are for Go 1.14.1 and are comparing against spaolacci/murmur3.

You will notice that at small sizes, the other library is better. This is due to this library converting to safe code for Go 1.14. At large sizes, this library is nearly identical to the other. On amd64, the 64 bit and 128 bit sums come out to ~9% faster.

32 bit sums:

32Sizes/32-12     3.00GB/s ± 1%  2.12GB/s ±11%  -29.24%  (p=0.000 n=9+10)
32Sizes/64-12     3.61GB/s ± 3%  2.79GB/s ± 8%  -22.62%  (p=0.000 n=10+10)
32Sizes/128-12    3.47GB/s ± 8%  2.79GB/s ± 4%  -19.47%  (p=0.000 n=10+10)
32Sizes/256-12    3.66GB/s ± 4%  3.25GB/s ± 6%  -11.09%  (p=0.000 n=10+10)
32Sizes/512-12    3.78GB/s ± 3%  3.54GB/s ± 4%   -6.30%  (p=0.000 n=9+9)
32Sizes/1024-12   3.86GB/s ± 3%  3.69GB/s ± 5%   -4.46%  (p=0.000 n=10+10)
32Sizes/2048-12   3.85GB/s ± 3%  3.81GB/s ± 3%     ~     (p=0.079 n=10+9)
32Sizes/4096-12   3.90GB/s ± 3%  3.82GB/s ± 2%   -2.14%  (p=0.029 n=10+10)
32Sizes/8192-12   3.82GB/s ± 3%  3.78GB/s ± 7%     ~     (p=0.529 n=10+10)

64/128 bit sums, non-amd64:

64Sizes/32-12     2.34GB/s ± 5%  2.64GB/s ± 9%  +12.87%  (p=0.000 n=10+10)
64Sizes/64-12     3.62GB/s ± 5%  3.96GB/s ± 4%   +9.41%  (p=0.000 n=10+10)
64Sizes/128-12    5.12GB/s ± 3%  5.44GB/s ± 4%   +6.09%  (p=0.000 n=10+9)
64Sizes/256-12    6.35GB/s ± 2%  6.27GB/s ± 9%     ~     (p=0.796 n=10+10)
64Sizes/512-12    6.58GB/s ± 7%  6.79GB/s ± 3%     ~     (p=0.075 n=10+10)
64Sizes/1024-12   7.49GB/s ± 3%  7.55GB/s ± 9%     ~     (p=0.393 n=10+10)
64Sizes/2048-12   8.06GB/s ± 2%  7.90GB/s ± 6%     ~     (p=0.156 n=9+10)
64Sizes/4096-12   8.27GB/s ± 6%  8.22GB/s ± 5%     ~     (p=0.631 n=10+10)
64Sizes/8192-12   8.35GB/s ± 4%  8.38GB/s ± 6%     ~     (p=0.631 n=10+10)
128Sizes/32-12    2.27GB/s ± 2%  2.68GB/s ± 5%  +18.00%  (p=0.000 n=10+10)
128Sizes/64-12    3.55GB/s ± 2%  4.00GB/s ± 3%  +12.47%  (p=0.000 n=8+9)
128Sizes/128-12   5.09GB/s ± 1%  5.43GB/s ± 3%   +6.65%  (p=0.000 n=9+9)
128Sizes/256-12   6.33GB/s ± 3%  5.65GB/s ± 4%  -10.79%  (p=0.000 n=9+10)
128Sizes/512-12   6.78GB/s ± 3%  6.74GB/s ± 6%     ~     (p=0.968 n=9+10)
128Sizes/1024-12  7.46GB/s ± 4%  7.56GB/s ± 4%     ~     (p=0.222 n=9+9)
128Sizes/2048-12  7.99GB/s ± 4%  7.96GB/s ± 3%     ~     (p=0.666 n=9+9)
128Sizes/4096-12  8.20GB/s ± 2%  8.25GB/s ± 4%     ~     (p=0.631 n=10+10)
128Sizes/8192-12  8.24GB/s ± 2%  8.26GB/s ± 5%     ~     (p=0.673 n=8+9)

64/128 bit sums, amd64:

64Sizes/32-12     2.34GB/s ± 5%  4.36GB/s ± 3%  +85.86%  (p=0.000 n=10+10)
64Sizes/64-12     3.62GB/s ± 5%  6.27GB/s ± 3%  +73.37%  (p=0.000 n=10+9)
64Sizes/128-12    5.12GB/s ± 3%  7.70GB/s ± 6%  +50.27%  (p=0.000 n=10+10)
64Sizes/256-12    6.35GB/s ± 2%  8.61GB/s ± 3%  +35.50%  (p=0.000 n=10+10)
64Sizes/512-12    6.58GB/s ± 7%  8.59GB/s ± 4%  +30.48%  (p=0.000 n=10+9)
64Sizes/1024-12   7.49GB/s ± 3%  8.81GB/s ± 2%  +17.66%  (p=0.000 n=10+10)
64Sizes/2048-12   8.06GB/s ± 2%  8.90GB/s ± 4%  +10.49%  (p=0.000 n=9+10)
64Sizes/4096-12   8.27GB/s ± 6%  8.90GB/s ± 4%   +7.54%  (p=0.000 n=10+10)
64Sizes/8192-12   8.35GB/s ± 4%  9.00GB/s ± 3%   +7.80%  (p=0.000 n=10+9)
128Sizes/32-12    2.27GB/s ± 2%  4.29GB/s ± 9%  +88.75%  (p=0.000 n=10+10)
128Sizes/64-12    3.55GB/s ± 2%  6.10GB/s ± 8%  +71.78%  (p=0.000 n=8+10)
128Sizes/128-12   5.09GB/s ± 1%  7.62GB/s ± 9%  +49.63%  (p=0.000 n=9+10)
128Sizes/256-12   6.33GB/s ± 3%  8.65GB/s ± 3%  +36.71%  (p=0.000 n=9+10)
128Sizes/512-12   6.78GB/s ± 3%  8.39GB/s ± 6%  +23.77%  (p=0.000 n=9+10)
128Sizes/1024-12  7.46GB/s ± 4%  8.70GB/s ± 4%  +16.70%  (p=0.000 n=9+10)
128Sizes/2048-12  7.99GB/s ± 4%  8.73GB/s ± 8%   +9.26%  (p=0.003 n=9+10)
128Sizes/4096-12  8.20GB/s ± 2%  8.86GB/s ± 6%   +8.00%  (p=0.000 n=10+10)
128Sizes/8192-12  8.24GB/s ± 2%  9.01GB/s ± 3%   +9.30%  (p=0.000 n=8+10)