435c0d9fc8
This PR switches the Nomad repository from using govendor to Go modules for managing dependencies. Aspects of the Nomad workflow remain pretty much the same. The usual Makefile targets should continue to work as they always did. The API submodule simply defers to the parent Nomad version on the repository, keeping the semantics of API versioning that currently exists.
2 KiB
xxhash
xxhash is a Go implementation of the 64-bit xxHash algorithm, XXH64. This is a high-quality hashing algorithm that is much faster than anything in the Go standard library.
This package provides a straightforward API:
func Sum64(b []byte) uint64
func Sum64String(s string) uint64
type Digest struct{ ... }
func New() *Digest
The Digest type implements hash.Hash64. Its key methods are:
func (*Digest) Write([]byte) (int, error)
func (*Digest) WriteString(string) (int, error)
func (*Digest) Sum64() uint64
This implementation provides a fast pure-Go implementation and an even faster assembly implementation for amd64.
Compatibility
This package is in a module and the latest code is in version 2 of the module. You need a version of Go with at least "minimal module compatibility" to use github.com/cespare/xxhash/v2:
- 1.9.7+ for Go 1.9
- 1.10.3+ for Go 1.10
- Go 1.11 or later
I recommend using the latest release of Go.
Benchmarks
Here are some quick benchmarks comparing the pure-Go and assembly implementations of Sum64.
| input size | purego | asm |
|---|---|---|
| 5 B | 979.66 MB/s | 1291.17 MB/s |
| 100 B | 7475.26 MB/s | 7973.40 MB/s |
| 4 KB | 17573.46 MB/s | 17602.65 MB/s |
| 10 MB | 17131.46 MB/s | 17142.16 MB/s |
These numbers were generated on Ubuntu 18.04 with an Intel i7-8700K CPU using the following commands under Go 1.11.2:
$ go test -tags purego -benchtime 10s -bench '/xxhash,direct,bytes'
$ go test -benchtime 10s -bench '/xxhash,direct,bytes'