blog_test.go

package blog

import (
	"testing"
)

type Advertisement struct {
	ID         int
	Name       string
	CampaignID int
	filler     [10]int
}

var Ads []Advertisement

func ads() []Advertisement {
	if len(Ads) == 0 {
		Ads = make([]Advertisement, 1e6)
		for i := range Ads {
			// pathological worst case - every campaign ID is unique
			Ads[i].CampaignID = i
		}
	}
	return Ads
}

func bench(b *testing.B, fn func([]Advertisement), N int) {
	ads := ads()[0:N]
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		fn(ads)
	}
}

func naive(ads []Advertisement) {
	index := map[int][]Advertisement{}
	for _, ad := range ads {
		index[ad.CampaignID] = []Advertisement{ad}
	}
}

func Benchmark_Naive_1e4(b *testing.B) { bench(b, naive, 1e4) }
func Benchmark_Naive_1e5(b *testing.B) { bench(b, naive, 1e5) }
func Benchmark_Naive_1e6(b *testing.B) { bench(b, naive, 1e6) }

func pointer(ads []Advertisement) {
	index := map[int][]*Advertisement{}
	for idx, ad := range ads {
		index[ad.CampaignID] = []*Advertisement{&ads[idx]}
	}
}

func Benchmark_Pointer_1e4(b *testing.B) { bench(b, pointer, 1e4) }
func Benchmark_Pointer_1e5(b *testing.B) { bench(b, pointer, 1e5) }
func Benchmark_Pointer_1e6(b *testing.B) { bench(b, pointer, 1e6) }

func position(ads []Advertisement) {
	index := map[int][]int{}
	for idx, ad := range ads {
		index[ad.CampaignID] = []int{idx}
	}
}

func Benchmark_Position_1e4(b *testing.B) { bench(b, position, 1e4) }
func Benchmark_Position_1e5(b *testing.B) { bench(b, position, 1e5) }
func Benchmark_Position_1e6(b *testing.B) { bench(b, position, 1e6) }