//Concurrency in “Go” Programming Language

Concurrency in “Go” Programming Language

Last week we discussed why you should consider leaving languages like Java and Python and switching to Go. I provided a quick example of how to write a web server using go, pretty easy right? This week I wanted to dive into something a bit more in depth to show off the power of Go: concurrency.

No real programming interview (in any programming language) is complete without a question about threads and or concurrency.   Whether you plan on using Go or not, and I highly recommend that you do, learning a few things on this topic will help you out in an interview, and maybe even in one of your classes.

Tip #1

Concurrency, although usually associated with multithreading, is NOT the same as multithreading. In fact, you can do concurrent programming in a single thread. Here is an example using Go.

In Go there is something called a channel.   Channels allow two goroutines to communicate.

Make a channel:

myChannel := make(chan int)

Push to a channel:

myChannel <- 42

Read from a channel:

value = <- myChannel  Channels can be used with select statements in Go. Here is an example: select {      case v1 := <- myChannel:            fmt.Printf(“%v from myChannel\n”, v1)      case v2 := <-c2:            fmt.Printf(“received %v from yourChannel \n”, v1)      case c3 <- 23:            fmt.Printf(“Sending data using select”, 23)      default:            fmt.Printf(“None of the channels were ready\n”)     } Here is a cool working example from http://play.golang.org/p/9U22NfrXeq // A concurrent prime sieve package main // Send the sequence 2, 3, 4, … to channel ‘ch’.func Generate(ch chan<- int) {       for i := 2; ; i++ {             ch <- i // Send ‘i’ to channel ‘ch’.       }} // Copy the values from channel ‘in’ to channel ‘out’,// removing those divisible by ‘prime’.func Filter(in <-chan int, out chan<- int, prime int) {       for {             i := <-in // Receive value from ‘in’.             if i%prime != 0 {                    out <- i // Send ‘i’ to ‘out’.             }       }}// The prime sieve: Daisy-chain Filter processes.func main() {       ch := make(chan int) // Create a new channel.       go Generate(ch)     // Launch Generate goroutine.       for i := 0; i < 10; i++ {             prime := <-ch             print(prime, “\n”)             ch1 := make(chan int)             go Filter(ch, ch1, prime)             ch = ch1       }}

Take a look and nuances here to really grasp some of the beauty of the Go programming language. See if you can figure out how this program works. I will discuss this further in upcoming articles. If you have any questions about Go, this program or this article drop me an email at etm8@njit.edu.







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Tom Maciejewski

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