Golang golang-dynparallel (snippet)

Go programming example 'golang-dynparallel'

golang-dynparallel

Golang beginners example: golang-dynparallel

package main

import (
    "fmt"
    "math/rand"
    "os"
    "runtime"
    "strconv"
    "time"
)

func check(e error) {
    if e != nil {
        panic(e)
    }
}

func Sqrt(n int) int {
    var t uint
    var b uint
    var r uint
    t = uint(n)
    p := uint(1 << 30)
    for p > t {
        p >>= 2
    }
    for ; p != 0; p >>= 2 {
        b = r | p
        r >>= 1
        if t >= b {
            t -= b
            r |= p
        }
    }
    return int(r)
}

func getPrime(n int) int {
    var primeList = []int{2}
    var isPrime int = 1
    var num int = 3
    var sqrtNum int = 0
    for len(primeList) < n {
        sqrtNum = Sqrt(num)
        for i := 0; i < len(primeList); i++ {
            if num%primeList[i] == 0 {
                isPrime = 0
            }
            if primeList[i] > sqrtNum {
                i = len(primeList)
            }
        }
        if isPrime == 1 {
            primeList = append(primeList, num)
        } else {
            isPrime = 1
        }
        num = num + 2
    }
    return primeList[n-1]
}

func enNmbr(input string) string {
    var lstc1 string
    var lstc2 int64
    intin, err2 := strconv.ParseInt(input, 10, 0)
    check(err2)

    lstc1 = input[len(input)-1:]
    if intin >= 10 {
        lstc2, _ = strconv.ParseInt(input[len(input)-2:], 10, 0)
    } else {
        lstc2 = 0
    }
    lstc1 = input[len(input)-1:]

    switch {
    case lstc2 > 10 && lstc2 < 20:
        return input + "th"
    case lstc1 == "1":
        return input + "st"
    case lstc1 == "2":
        return input + "nd"
    case lstc1 == "3":
        return input + "rd"
    default:
        return input + "th"
    }
    return ""
}

func main() {
    var nprocs int
    if len(os.Args) >= 2 {
        nprocs, _ = strconv.Atoi(os.Args[1])
    } else {
        fmt.Println("Enter a number")
        _, err1 := fmt.Scanf("%d", &nprocs)
        check(err1)
    }
    if nprocs < 2 {
        panic("input to low")
    }

    fmt.Println("setting max processes to: ", nprocs)
    runtime.GOMAXPROCS(nprocs)

    var prime int
    var random int
    channels := make([]chan int, nprocs)
    for i := 0; i < nprocs; i++ {
        channels[i] = make(chan int)
    }

    for i := 0; i < nprocs; i++ {
        rand.Seed(time.Now().UnixNano() + int64(i))
        random = rand.Intn(6400) + 1
        fmt.Printf("sending request for the %v prime number on channel %v\n", enNmbr(strconv.Itoa(random)), i)
        go func(ch chan int, random int, i int) {
            time.Sleep(time.Duration(random) * time.Millisecond)
            fmt.Printf("calculating the %v prime number for channel %v\n", enNmbr(strconv.Itoa(random)), i)
            prime = getPrime(random)
            ch <- prime
        }(channels[i], random, i)
    }

    var chancount int = 0
    for {
        for i := 0; i < nprocs; i++ {
            select {
            case v := <-channels[i]:
                fmt.Printf("received %v from channel %v\n", v, i)
                chancount++
            default:
            }
        }
        if chancount == nprocs {
            break
        }

    }
}

Useful links

• Learn Go: https://golangr.com
• Download Go: https://golang.org