Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

Parallel processing in golang

Given the following code:

package main

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

func main() {
    for i := 0; i < 3; i++ {
        go f(i)
    }

    // prevent main from exiting immediately
    var input string
    fmt.Scanln(&input)
}

func f(n int) {
    for i := 0; i < 10; i++ {
        dowork(n, i)
        amt := time.Duration(rand.Intn(250))
        time.Sleep(time.Millisecond * amt)
    }
}

func dowork(goroutine, loopindex int) {
    // simulate work
    time.Sleep(time.Second * time.Duration(5))
    fmt.Printf("gr[%d]: i=%d\n", goroutine, loopindex)
}

Can i assume that the 'dowork' function will be executed in parallel?

Is this a correct way of achieving parallelism or is it better to use channels and separate 'dowork' workers for each goroutine?

like image 404
wilsonfiifi Avatar asked Aug 03 '14 16:08

wilsonfiifi


People also ask

How does Golang handle concurrency?

In Go, concurrency works through the use of in-built functions known as Goroutines. Goroutines are functions, unique to Go, that run at the same time alongside other code or programs. They're not OS threads, though, they may be considered lightweight threads.

What is an example of parallel processing?

In parallel processing, we take in multiple different forms of information at the same time. This is especially important in vision. For example, when you see a bus coming towards you, you see its color, shape, depth, and motion all at once.

What is multithreading Golang?

In multi-threading, the OS controls the threads, if the threads are more than the CPU, the OS makes the threads are switched to use the CPU. This is called the Context switching. The context switching is when multiple threads run on a CPU, it makes the threads switch to use the CPU.

What is the difference between concurrency and parallelism in Golang?

1. Concurrency is the task of running and managing the multiple computations at the same time. While parallelism is the task of running multiple computations simultaneously.


1 Answers

Regarding GOMAXPROCS, you can find this in Go 1.5's release docs:

By default, Go programs run with GOMAXPROCS set to the number of cores available; in prior releases it defaulted to 1.

Regarding preventing the main function from exiting immediately, you could leverage WaitGroup's Wait function.

I wrote this utility function to help parallelize a group of functions:

import "sync"

// Parallelize parallelizes the function calls
func Parallelize(functions ...func()) {
    var waitGroup sync.WaitGroup
    waitGroup.Add(len(functions))

    defer waitGroup.Wait()

    for _, function := range functions {
        go func(copy func()) {
            defer waitGroup.Done()
            copy()
        }(function)
    }
}

So in your case, we could do this

func1 := func() {
    f(0)
}

func2 = func() {
    f(1)
}

func3 = func() {
    f(2)
}

Parallelize(func1, func2, func3)

If you wanted to use the Parallelize function, you can find it here https://github.com/shomali11/util

like image 115
Raed Shomali Avatar answered Sep 28 '22 16:09

Raed Shomali