goimagehash/imagehash19.go

//go:build go1.9
// +build go1.9

package goimagehash

import (
	"math/bits"
)

func popcnt(x uint64) int { return bits.OnesCount64(x) }
Make compliant with python imagehash 2024-04-05 16:29:03 -07:00			`//go:build go1.9`
Use bits.OnesCount64 when available Benchmark on i7-2600k, which has the POPCNT instruction: name old time/op new time/op delta DistanceIdentical-8 5.08ns ± 0% 1.01ns ± 1% -80.07% (p=0.008 n=5+5) DistanceDifferent-8 81.5ns ± 2% 1.0ns ± 0% -98.76% (p=0.016 n=5+4) Benchmark on Cavium Octeon, a MIPS64 platform with no dedicated instruction: name old time/op new time/op delta DistanceIdentical-2 120ns ± 6% 144ns ± 5% +19.93% (p=0.008 n=5+5) DistanceDifferent-2 656ns ± 4% 144ns ± 4% -78.09% (p=0.008 n=5+5) 2018-05-02 06:40:49 -07:00			`// +build go1.9`

			`package goimagehash`

			`import (`
			`"math/bits"`
			`)`

			`func popcnt(x uint64) int { return bits.OnesCount64(x) }`