lukechampine
61 lines
2.2 KiB
Markdown
61 lines
2.2 KiB
Markdown
fastxor
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-----
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[](https://godoc.org/github.com/lukechampine/fastxor)
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[](https://goreportcard.com/report/github.com/lukechampine/fastxor)
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```
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go get github.com/lukechampine/fastxor
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```
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Is there a gaping hole in your heart that can only be filled by xor'ing byte
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streams at 20GB/s? If so, you've come to the right place.
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`fastxor` is exactly what it sounds like: a package that xors bytes as fast
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as your CPU is capable of. For best results, use a CPU that supports a SIMD
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instruction set like SSE or AVX. On other architectures, performance is much
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less impressive, but still faster than a naive byte-wise loop.
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I wrote this package to try my hand at writing Go assembly, so please scrutinize
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my code and let me know how I could make it faster or cleaner!
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# Benchmarks
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```
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AVX:
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BenchmarkBytes/16-4 200000000 8.72 ns/op 1835.82 MB/s
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BenchmarkBytes/1024-4 50000000 38.1 ns/op 26850.41 MB/s
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BenchmarkBytes/65k-4 500000 2738 ns/op 23930.93 MB/s
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SSE:
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BenchmarkBytes/16-4 200000000 8.63 ns/op 1852.98 MB/s
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BenchmarkBytes/1024-4 50000000 39.4 ns/op 25993.00 MB/s
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BenchmarkBytes/65k-4 500000 2733 ns/op 23975.08 MB/s
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Word-wise:
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BenchmarkBytes/16-4 100000000 10.5 ns/op 1521.66 MB/s
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BenchmarkBytes/1024-4 10000000 125 ns/op 8163.59 MB/s
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BenchmarkBytes/65k-4 200000 6895 ns/op 9504.62 MB/s
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Byte-wise:
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BenchmarkBytes/16-4 100000000 17.3 ns/op 925.16 MB/s
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BenchmarkBytes/1024-4 2000000 841 ns/op 1216.31 MB/s
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BenchmarkBytes/65k-4 30000 54100 ns/op 1211.38 MB/s
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```
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Conclusions: `fastxor` is 2-25 times faster than a naive `for` loop. AVX and
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SSE performance is roughly equivalent, which makes me suspect that I may be
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doing something wrong. Lastly, for very small slices, the cost of the function
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call starts to outweigh the benefit of AVX/SSE (the Go compiler never inlines
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handwritten asm). If you need to xor exactly 16 bytes (common in block
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ciphers), the specialized `Block` function outperforms the more generic
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`Bytes`:
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```
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BenchmarkBlock-4 500000000 3.69 ns/op 4337.88 MB/s
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``` |