Awesome
Not needed!
If you use Go 1.7 or later, there is no reason to use this package any more, since optimizations have been merged into the standard library.
The following reposiitory and documentation is left for historical reasons (and to not break exisiting code).
crc32
This package is a drop-in replacement for the standard library hash/crc32 package, that features SSE 4.2 optimizations on x64 platforms, for a 10x speedup.
usage
Install using go get github.com/klauspost/crc32. This library is based on Go 1.5 code and requires Go 1.3 or newer.
Replace import "hash/crc32" with import "github.com/klauspost/crc32" and you are good to go.
changes
- Oct 20, 2016: Changes have been merged to upstream Go. Package updated to match.
- Dec 4, 2015: Uses the "slice-by-8" trick more extensively, which gives a 1.5 to 2.5x speedup if assembler is unavailable.
performance
For Go 1.7 performance is equivalent to the standard library. So if you use this package for Go 1.7 you can switch back.
For IEEE tables (the most common), there is approximately a factor 10 speedup with "CLMUL" (Carryless multiplication) instruction:
benchmark old ns/op new ns/op delta
BenchmarkCrc32KB 99955 10258 -89.74%
benchmark old MB/s new MB/s speedup
BenchmarkCrc32KB 327.83 3194.20 9.74x
For other tables and "CLMUL" capable machines the performance is the same as the standard library.
Here are some detailed benchmarks, comparing to go 1.5 standard library with and without assembler enabled.
Std: Standard Go 1.5 library
Crc: Indicates IEEE type CRC.
40B: Size of each slice encoded.
NoAsm: Assembler was disabled (ie. not an AMD64 or SSE 4.2+ capable machine).
Castagnoli: Castagnoli CRC type.
BenchmarkStdCrc40B-4 10000000 158 ns/op 252.88 MB/s
BenchmarkCrc40BNoAsm-4 20000000 105 ns/op 377.38 MB/s (slice8)
BenchmarkCrc40B-4 20000000 105 ns/op 378.77 MB/s (slice8)
BenchmarkStdCrc1KB-4 500000 3604 ns/op 284.10 MB/s
BenchmarkCrc1KBNoAsm-4 1000000 1463 ns/op 699.79 MB/s (slice8)
BenchmarkCrc1KB-4 3000000 396 ns/op 2583.69 MB/s (asm)
BenchmarkStdCrc8KB-4 200000 11417 ns/op 717.48 MB/s (slice8)
BenchmarkCrc8KBNoAsm-4 200000 11317 ns/op 723.85 MB/s (slice8)
BenchmarkCrc8KB-4 500000 2919 ns/op 2805.73 MB/s (asm)
BenchmarkStdCrc32KB-4 30000 45749 ns/op 716.24 MB/s (slice8)
BenchmarkCrc32KBNoAsm-4 30000 45109 ns/op 726.42 MB/s (slice8)
BenchmarkCrc32KB-4 100000 11497 ns/op 2850.09 MB/s (asm)
BenchmarkStdNoAsmCastagnol40B-4 10000000 161 ns/op 246.94 MB/s
BenchmarkStdCastagnoli40B-4 50000000 28.4 ns/op 1410.69 MB/s (asm)
BenchmarkCastagnoli40BNoAsm-4 20000000 100 ns/op 398.01 MB/s (slice8)
BenchmarkCastagnoli40B-4 50000000 28.2 ns/op 1419.54 MB/s (asm)
BenchmarkStdNoAsmCastagnoli1KB-4 500000 3622 ns/op 282.67 MB/s
BenchmarkStdCastagnoli1KB-4 10000000 144 ns/op 7099.78 MB/s (asm)
BenchmarkCastagnoli1KBNoAsm-4 1000000 1475 ns/op 694.14 MB/s (slice8)
BenchmarkCastagnoli1KB-4 10000000 146 ns/op 6993.35 MB/s (asm)
BenchmarkStdNoAsmCastagnoli8KB-4 50000 28781 ns/op 284.63 MB/s
BenchmarkStdCastagnoli8KB-4 1000000 1029 ns/op 7957.89 MB/s (asm)
BenchmarkCastagnoli8KBNoAsm-4 200000 11410 ns/op 717.94 MB/s (slice8)
BenchmarkCastagnoli8KB-4 1000000 1000 ns/op 8188.71 MB/s (asm)
BenchmarkStdNoAsmCastagnoli32KB-4 10000 115426 ns/op 283.89 MB/s
BenchmarkStdCastagnoli32KB-4 300000 4065 ns/op 8059.13 MB/s (asm)
BenchmarkCastagnoli32KBNoAsm-4 30000 45171 ns/op 725.41 MB/s (slice8)
BenchmarkCastagnoli32KB-4 500000 4077 ns/op 8035.89 MB/s (asm)
The IEEE assembler optimizations has been submitted and will be part of the Go 1.6 standard library.
However, the improved use of slice-by-8 has not, but will probably be submitted for Go 1.7.
license
Standard Go license. Changes are Copyright (c) 2015 Klaus Post under same conditions.