oz-lotto/main.go

package main

import (
	"flag"
	"fmt"
	"math/rand"
	"runtime"
	"sort"
	"sync"
	"time"
)

// const
const (
	NumberCount    = 7
	MaximumResults = 50
	Routines       = 10
)

var (
	syncWinners sync.Map
	signals     = make(chan bool, Routines)
)

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU())
	timesInput := flag.Int("t", 100000, "an int")
	flag.Parse()
	times := *timesInput

	now := time.Now()

	startTime := now.Unix()

	fmt.Printf("Started at %v to run lottery for %v times \n", now, times)
	for routine := 0; routine < Routines; routine++ {
		go func() {
			for i := 0; i < times/Routines; i++ {
				winner := run()
				if currentTimes, ok := syncWinners.Load(winner); ok {
					currentTimesInt := currentTimes.(int)
					syncWinners.Store(winner, currentTimesInt+1)
				} else {
					syncWinners.Store(winner, 1)
				}
			}
			signals <- true
		}()
	}

	routineReturnTimes := 0
	for range signals {
		routineReturnTimes++
		fmt.Println(routineReturnTimes)
		if routineReturnTimes == Routines {
			close(signals)
		}
	}

	fmt.Printf("Calculation finished at : %v \n", time.Now())
	// only print out top numbers
	type kv struct {
		Key   [NumberCount]int
		Value int
	}

	var ss []kv

	syncWinners.Range(func(key interface{}, value interface{}) bool {
		winningTimes := value.(int)
		winningNumber := key.([7]int)
		if winningTimes > 1 {
			ss = append(ss, kv{winningNumber, winningTimes})
		}
		return true
	})

	sort.Slice(ss, func(i, j int) bool {
		return ss[i].Value > ss[j].Value
	})

	fmt.Printf("Sorting finished at : %v \n", time.Now())

	index := 0
	for _, kv := range ss {
		// only pick the top numbers
		if index > MaximumResults {
			break
		}
		fmt.Printf("%v, %d \n", kv.Key, kv.Value)
		index++
	}
	fmt.Printf("The process takes about: %v seconds", time.Now().Unix()-startTime)
}

func run() [7]int {
	var winNumbers []int
	// generate the randomised numbers
	list := rand.Perm(45)
	// because perm generate [0,45) but we need [1,45]
	for index, item := range list {
		list[index] = item + 1
	}

	rand.Seed(time.Now().UnixNano())

	indexes := make([]int, 0)

	for i := 0; i < NumberCount; i++ {
		pickedIndex := pickIndex(indexes, len(list))
		indexes = append(indexes, pickedIndex)

		//pick random number
		chosen := list[pickedIndex]

		winNumbers = append(winNumbers, chosen)
	}

	sort.Ints(winNumbers)
	var arr [NumberCount]int
	copy(arr[:], winNumbers)

	return arr

}

func pickIndex(indexes []int, length int) int {
	chosen := rand.Intn(length - 1)
	// make sure the index only exist once
	for _, value := range indexes {
		if value == chosen {
			return pickIndex(indexes, length)
		}
	}

	return chosen
}