iterator.go

package main

import (
	"sync/atomic"
)

type sample struct {
	t int64
	v float64
}

type simpleIterator struct {
	vals []sample
	i    int
}

func newSimpleIterator(vals []sample) *simpleIterator {
	return &simpleIterator{
		vals: vals,
		i:    -1,
	}
}

func (si *simpleIterator) Next() bool {
	si.i++
	return si.i < len(si.vals)
}

func (si *simpleIterator) At() (int64, float64) {
	return si.vals[si.i].t, si.vals[si.i].v
}

func (si *simpleIterator) Reset() {
	si.i = -1
}

type countingIterator struct {
	counter *int64
	it      *simpleIterator
}

func newCountingIterator(c *int64, it *simpleIterator) *countingIterator {
	return &countingIterator{c, it}
}

func (ci countingIterator) At() (int64, float64) {
	atomic.AddInt64(ci.counter, 1)
	return ci.it.At()
}

func (ci countingIterator) Next() bool { return ci.it.Next() }

func (ci countingIterator) Reset() { ci.it.Reset() }

iterator_test.go

package main

import "testing"

func benchmarkSimple(n int, b *testing.B) {
	si := newSimpleIterator(generateSamples(n))
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		for si.Next() {
			si.At()
		}

		si.Reset()
	}
}

func benchmarkCounting(n int, b *testing.B) {
	si := newSimpleIterator(generateSamples(n))
	var ctr int64
	ci := newCountingIterator(&ctr, si)
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		for ci.Next() {
			ci.At()
		}

		ci.Reset()
	}
}

func BenchmarkSimple1000(b *testing.B)   { benchmarkSimple(1000, b) }
func BenchmarkSimple10000(b *testing.B)  { benchmarkSimple(10000, b) }
func BenchmarkSimple100000(b *testing.B) { benchmarkSimple(100000, b) }

func BenchmarkCounting1000(b *testing.B)   { benchmarkCounting(1000, b) }
func BenchmarkCounting10000(b *testing.B)  { benchmarkCounting(10000, b) }
func BenchmarkCounting100000(b *testing.B) { benchmarkCounting(100000, b) }

func generateSamples(n int) []sample {
	s := make([]sample, 0, n)
	for i := 0; i < n; i++ {
		s = append(s, sample{})
	}

	return s
}

results

➜  bench-atomic-iterator go test -bench=.
goos: linux
goarch: amd64
pkg: github.com/gouthamve/x/bench-atomic-iterator
BenchmarkSimple1000-8       	 1000000	      1475 ns/op
BenchmarkSimple10000-8      	  100000	     14000 ns/op
BenchmarkSimple100000-8     	   10000	    136397 ns/op
BenchmarkCounting1000-8     	  200000	      6928 ns/op
BenchmarkCounting10000-8    	   20000	     68760 ns/op
BenchmarkCounting100000-8   	    2000	    679316 ns/op
PASS
ok  	github.com/gouthamve/x/bench-atomic-iterator	9.379s


============== NEW RESULTS BELOW ===============
➜  bench-atomic-iterator go test -bench=.
goos: linux
goarch: amd64
pkg: github.com/gouthamve/x/bench-atomic-iterator
BenchmarkSimple1000-8       	1384 ns/op
BenchmarkSimple10000-8      	13729 ns/op
BenchmarkSimple100000-8       137595 ns/op

BenchmarkCounting1000-8     	1837 ns/op
BenchmarkCounting10000-8    	18678 ns/op
BenchmarkCounting100000-8     187173 ns/op
PASS
ok  	github.com/gouthamve/x/bench-atomic-iterator	10.118s