slice chunk

gistfile1.txt

goos: darwin
goarch: amd64
pkg: perf
BenchmarkBulk
BenchmarkBulk/re
BenchmarkBulk/re-4         	15252195	        67.9 ns/op	      48 B/op	       1 allocs/op
BenchmarkBulk/slow
BenchmarkBulk/slow-4       	  224365	      5269 ns/op	   12352 B/op	      29 allocs/op
PASS

slice_test.go

package main

import "testing"

func BenchmarkBulk(b *testing.B) {
	const bulk = 50
	const max = 1400
	var ids = make([]int, max)
	for i, _ := range ids {
		ids[i] = i
	}
	b.Run("re", func(b *testing.B) {
		var dup = make([]int, max)
		copy(dup, ids)
		b.ReportAllocs()
		for i := 0; i < b.N; i++ {
			var chunks = make([][]int, 0, len(dup)/bulk+1)
			for bulk < len(dup) {
				chunks, dup = append(chunks, dup[:bulk]), dup[bulk:]
			}
			chunks = append(chunks, dup)
		}
	})
	b.Run("slow", func(b *testing.B) {
		var dup = make([]int, max)
		copy(dup, ids)
		b.ReportAllocs()
		for i := 0; i < b.N; i++ {
			var chunks = make([][]int, 0, len(dup)/bulk+1)
			var slice []int = make([]int, 0, bulk)
			var i int
			for _, id := range dup {
				if i < bulk {
					slice = append(slice, id)
					i++
				} else {
					chunks = append(chunks, slice)
					slice = make([]int, 0, bulk)
					slice = append(slice, id)
					i = 1
				}
			}
			chunks = append(chunks, slice)
		}
	})
}