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77 lines
2.8 KiB
Markdown
77 lines
2.8 KiB
Markdown
[](https://travis-ci.org/valyala/fastrand)
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[](http://godoc.org/github.com/valyala/fastrand)
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[](https://goreportcard.com/report/github.com/valyala/fastrand)
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# fastrand
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Fast pseudorandom number generator.
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# Features
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- Optimized for speed.
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- Performance scales on multiple CPUs.
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# How does it work?
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It abuses [sync.Pool](https://golang.org/pkg/sync/#Pool) for maintaining
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"per-CPU" pseudorandom number generators.
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TODO: firgure out how to use real per-CPU pseudorandom number generators.
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# Benchmark results
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```
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$ GOMAXPROCS=1 go test -bench=. github.com/valyala/fastrand
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goos: linux
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goarch: amd64
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pkg: github.com/valyala/fastrand
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BenchmarkUint32n 50000000 29.7 ns/op
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BenchmarkRNGUint32n 200000000 6.50 ns/op
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BenchmarkRNGUint32nWithLock 100000000 21.5 ns/op
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BenchmarkMathRandInt31n 50000000 31.8 ns/op
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BenchmarkMathRandRNGInt31n 100000000 17.9 ns/op
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BenchmarkMathRandRNGInt31nWithLock 50000000 30.2 ns/op
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PASS
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ok github.com/valyala/fastrand 10.634s
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```
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```
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$ GOMAXPROCS=2 go test -bench=. github.com/valyala/fastrand
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goos: linux
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goarch: amd64
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pkg: github.com/valyala/fastrand
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BenchmarkUint32n-2 100000000 17.6 ns/op
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BenchmarkRNGUint32n-2 500000000 3.36 ns/op
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BenchmarkRNGUint32nWithLock-2 50000000 32.0 ns/op
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BenchmarkMathRandInt31n-2 20000000 51.2 ns/op
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BenchmarkMathRandRNGInt31n-2 100000000 11.0 ns/op
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BenchmarkMathRandRNGInt31nWithLock-2 20000000 91.0 ns/op
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PASS
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ok github.com/valyala/fastrand 9.543s
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```
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```
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$ GOMAXPROCS=4 go test -bench=. github.com/valyala/fastrand
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goos: linux
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goarch: amd64
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pkg: github.com/valyala/fastrand
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BenchmarkUint32n-4 100000000 14.2 ns/op
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BenchmarkRNGUint32n-4 500000000 3.30 ns/op
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BenchmarkRNGUint32nWithLock-4 20000000 88.7 ns/op
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BenchmarkMathRandInt31n-4 10000000 145 ns/op
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BenchmarkMathRandRNGInt31n-4 200000000 8.35 ns/op
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BenchmarkMathRandRNGInt31nWithLock-4 20000000 102 ns/op
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PASS
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ok github.com/valyala/fastrand 11.534s
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```
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As you can see, [fastrand.Uint32n](https://godoc.org/github.com/valyala/fastrand#Uint32n)
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scales on multiple CPUs, while [rand.Int31n](https://golang.org/pkg/math/rand/#Int31n)
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doesn't scale. Their performance is comparable on `GOMAXPROCS=1`,
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but `fastrand.Uint32n` runs 3x faster than `rand.Int31n` on `GOMAXPROCS=2`
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and 10x faster than `rand.Int31n` on `GOMAXPROCS=4`.
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