72 lines
2.3 KiB
Markdown
72 lines
2.3 KiB
Markdown
# xxhash
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[](https://pkg.go.dev/github.com/cespare/xxhash/v2)
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[](https://github.com/cespare/xxhash/actions/workflows/test.yml)
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xxhash is a Go implementation of the 64-bit [xxHash] algorithm, XXH64. This is a
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high-quality hashing algorithm that is much faster than anything in the Go
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standard library.
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This package provides a straightforward API:
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```
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func Sum64(b []byte) uint64
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func Sum64String(s string) uint64
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type Digest struct{ ... }
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func New() *Digest
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```
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The `Digest` type implements hash.Hash64. Its key methods are:
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```
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func (*Digest) Write([]byte) (int, error)
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func (*Digest) WriteString(string) (int, error)
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func (*Digest) Sum64() uint64
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```
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The package is written with optimized pure Go and also contains even faster
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assembly implementations for amd64 and arm64. If desired, the `purego` build tag
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opts into using the Go code even on those architectures.
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[xxHash]: http://cyan4973.github.io/xxHash/
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## Compatibility
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This package is in a module and the latest code is in version 2 of the module.
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You need a version of Go with at least "minimal module compatibility" to use
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github.com/cespare/xxhash/v2:
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* 1.9.7+ for Go 1.9
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* 1.10.3+ for Go 1.10
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* Go 1.11 or later
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I recommend using the latest release of Go.
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## Benchmarks
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Here are some quick benchmarks comparing the pure-Go and assembly
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implementations of Sum64.
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| input size | purego | asm |
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| ---------- | --------- | --------- |
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| 4 B | 1.3 GB/s | 1.2 GB/s |
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| 16 B | 2.9 GB/s | 3.5 GB/s |
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| 100 B | 6.9 GB/s | 8.1 GB/s |
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| 4 KB | 11.7 GB/s | 16.7 GB/s |
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| 10 MB | 12.0 GB/s | 17.3 GB/s |
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These numbers were generated on Ubuntu 20.04 with an Intel Xeon Platinum 8252C
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CPU using the following commands under Go 1.19.2:
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```
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benchstat <(go test -tags purego -benchtime 500ms -count 15 -bench 'Sum64$')
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benchstat <(go test -benchtime 500ms -count 15 -bench 'Sum64$')
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```
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## Projects using this package
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- [InfluxDB](https://github.com/influxdata/influxdb)
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- [Prometheus](https://github.com/prometheus/prometheus)
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- [VictoriaMetrics](https://github.com/VictoriaMetrics/VictoriaMetrics)
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- [FreeCache](https://github.com/coocood/freecache)
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- [FastCache](https://github.com/VictoriaMetrics/fastcache)
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