simple sample

golang-sample.go

package main

import (
	"fmt"
	"math/rand"
	"sync"
	"time"

	"github.com/wrfly/gua"
)

type c struct {
	Ratio float32 `default:"0.5" desc:"sample ratio"`
	Total uint    `default:"1000" desc:"total number to test"`
}

const bucketSize = 100

type sampler struct {
	ratio float32

	m       sync.RWMutex
	i       uint8
	buckets []bool

	threshold int32
}

func (s *sampler) pass() bool {
	return rand.Int31n(bucketSize) < s.threshold
}

func (s *sampler) pass1() bool {
	s.m.RLock()
	s.i++
	s.i = s.i % bucketSize
	x := s.i
	s.m.RUnlock()
	return s.buckets[x]
}

func (s *sampler) resetRatio(ratio float32) {
	if ratio > 1 || ratio < 0 {
		panic("bad ratio, must in [0,1]")
	}

	s.m.Lock()

	s.ratio = ratio
	s.threshold = int32(ratio * 100)

	buckets := make([]bool, bucketSize)
	for i := 0; i < int(ratio*100); i++ {
		random := rand.Int31n(bucketSize)
		if buckets[random] {
			i--
		} else {
			buckets[random] = true
		}
	}
	s.buckets = buckets

	s.m.Unlock()
}

func newSampler(ratio float32) *sampler {
	s := &sampler{}
	s.resetRatio(ratio)
	return s
}

func main() {
	config := new(c)
	gua.Parse(config)

	var (
		passed uint
		i      uint
	)
	s := newSampler(config.Ratio)

	start := time.Now()
	for ; i < config.Total; i++ {
		if s.pass1() {
			passed++
		}
	}
	printResult(s, passed, config.Total, start)

	passed, i = 0, 0
	start = time.Now()
	for ; i < config.Total; i++ {
		if s.pass1() {
			passed++
		}
	}
	printResult(s, passed, config.Total, start)

	passed, i = 0, 0
	start = time.Now()
	for ; i < config.Total; i++ {
		if s.pass() {
			passed++
		}
	}
	printResult(s, passed, config.Total, start)

	fmt.Println()
}

func printResult(s *sampler, passed, total uint, start time.Time) {
	fmt.Printf("ratio=%.2f result=%.2f%% (%d/%d) [%s]\n",
		s.ratio,
		float32(passed)/float32(total)*100,
		passed, total, time.Now().Sub(start))
}