Difference between concurrency and parallelism with Golang code examples

In this post, I will explain the differences between concurrency and parallelism. After that, I will give code examples using Golang.

Concurrency and parallelism are related concepts in computer science but they have different meanings.

Concurrency refers to the concept of executing multiple tasks at the same time, where jobs are interleaved in an overlapping manner in order to give an illusion of simultaneous execution.

Parallelism, on the other hand, refers to the execution of multiple tasks simultaneously using multiple processors or cores in a computer system. The tasks in parallelism run simultaneously, side by side, on different processors, unlike in concurrency where tasks are interleaved.

From the above, you can know that concurrency is about managing lots of things at once. parallelism is about doing lots of things at once.

That’s the key difference between concurrency and parallelism.

In simple terms, the first and most essential difference is that concurrency is about dealing with lots of things at once, while parallelism is about doing lots of things at the same time. The other important difference is that concurrency runs on the same processor, and parallelism runs on at least two processors.

Now, we understand the differences between concurrency and parallelism. But how about implementing them in Golang? Let’s make hard dirty.

I will give four examples. In the first two examples, the results don’t show differences clearly. In the second two examples, you will see a clear difference. All codes you can paste in your local directly.

First, the two examples’ differences are not clear

Concurrency

The following code uses Golang to implement the concurrency example.

package main

import (
 "fmt"
 "sync"
 "time"
)

func printNumbersConcurrently(wg *sync.WaitGroup) {
   for i := 1; i <= 10; i++ {
      time.Sleep(100 * time.Millisecond)…