Golang Concurrency Part I

Concurrent programming knowledge a necessity these days. Servers need to handle multiple connections and process them simultaniously. Mobile apps are working in a manner that, foreground and backgroung processing is done in saperate context. Since processors are growing in numbers not in speed, we need to design out programs in such a manner.

Go let us use two types of Concurrent Programming:
1. Communicating sequential processes (CSP).
2. Shared memory multi-threaded programming (Traditional).

Goroutines

Goroutines are not threads, but they are like threads. Each concurrently executing activity is called Goroutine. As an example assume a problem in which we are processing multiple types of data and writing in multiple files. So, there are two ways to do that.

1. Sequential programming.
2. Concurrent programming.

I will just create an example, and will show you it’s really easy to convert a sequential program to concurrent program in go.

A concurrent file writing program:

Sequential Implementation:

package main

import (
       "os"
       "fmt"
)

var filenamearray []string

func processData(index int) {
       f, _ := os.OpenFile(filenamearray[index],os.O_RDWR | os.O_CREATE,0777) // skipping error
       defer f.Close()
       for i := 0;i<10000000;i++ {
              a := i + index
              fmt.Fprintln(f,a)
       }
}

func main() {

       filenamearray = []string{"a1", "a2", "a3","a4"}

       for i:=0;i<len(filenamearray) ;i++ {
              processData(i)
       }


}

 

Concurrent Implementation:

import (
       "os"
       "fmt"
       "sync"
)

var filenamearray []string

var wg sync.WaitGroup

func processData(index int) {
       f, _ := os.OpenFile(filenamearray[index],os.O_RDWR | os.O_CREATE,0777) // skipping error
       defer wg.Done()
       defer f.Close()

       for i := 0;i<10000000;i++ {
              a := i + index
              fmt.Fprintln(f,a)
       }
}

func main() {

       filenamearray = []string{"a1", "a2", "a3","a4"}

       for i:=0;i<len(filenamearray) ;i++ {
              wg.Add(1)
              go processData(i)
       }

       wg.Wait()

}

When I tried to run both the programs, there was a huge difference in performance:

Sequential took : 1 Minute and 21 seconds approx.

Concurrent took : 28 seconds. 

You can test by changing the number of files.

I the next part I will cover channels, with a practical example. Till then, Happy Coding.