Benchmark for a generic func: simple loop vs. calling slices.Index

removeFirstByValue_test.go

package bench

import (
	"testing"

	"golang.org/x/exp/slices"
)

func BenchmarkRemoveFirstByValue(b *testing.B) {
	items := []string{"a", "b", "c", "d", "e", "f", "g", "h"}
	for i := 0; i < b.N; i++ {
		items = removeFirstByValue(items, "d")
		items = slices.Insert(items, 3, "d")
	}
}

func BenchmarkRemoveFirstByValueIndex(b *testing.B) {
	items := []string{"a", "b", "c", "d", "e", "f", "g", "h"}
	for i := 0; i < b.N; i++ {
		items = removeFirstByValueIndex(items, "d")
		items = slices.Insert(items, 3, "d")
	}
}

func removeFirstByValue[T comparable](items []T, x T) []T {
	for i, y := range items {
		if y == x {
			return slices.Delete(items, i, i+1)
		}
	}
	return items
}

func removeFirstByValueIndex[S ~[]T, T comparable](items S, x T) S {
	if i := slices.Index(items, x); i != -1 {
		return slices.Delete(items, i, i+1)
	}
	return items
}

On my workstation:

% go test -bench=. -benchtime=30s
goos: darwin
goarch: amd64
cpu: VirtualApple @ 2.50GHz
BenchmarkRemoveFirstByValue-10         	1000000000	        28.47 ns/op
BenchmarkRemoveFirstByValueIndex-10    	1000000000	        28.90 ns/op