Comparison of coroutines and threads in Go language

In the Go language, Goroutine and Thread are both mechanisms used to run concurrent code. Although their functions are similar, there are some differences in their implementation and use. This article will explore the difference between coroutines and threads in the Go language through specific code examples, and help readers better understand the differences between them.

1. The concepts of coroutines and threads

Coroutines are lightweight concurrency units in the Go language and can be regarded as a lightweight thread. . Coroutines are managed by the Go runtime and have small stack space and low creation and destruction overhead, allowing a large number of coroutines to be created for concurrent execution without worrying about waste of resources.

Threads are concurrent execution units at the operating system level and are managed by the operating system kernel. Each thread has its own stack space and registers. The creation and destruction of threads is expensive, so it is impossible to create a large number of concurrently executing threads like coroutines.

2. Example of using coroutine

The following is a simple example code of using coroutine:

package main

import (
    "fmt"
    "time"
)

func printNumbers() {
    for i := 1; i <= 5; i++ {
        fmt.Println(i)
    }
}

func main() {
    go printNumbers()
    
    time.Sleep(1 * time.Second)
    fmt.Println("Main goroutine exits")
}

In the above code, printNumbersThe function is started as a coroutine, which prints the numbers 1 to 5. In the main function, use the go keyword to start the printNumbers coroutine, and let the main function wait for 1 second through the time.Sleep function to ensure that the coroutine Enough time to execute. Finally, the main function outputs "Main goroutine exits".

3. Example of using threads

The following is a simple example code of using threads:

package main

import (
    "fmt"
    "sync"
)

var wg sync.WaitGroup

func printNumbers() {
    defer wg.Done()

    for i := 1; i <= 5; i++ {
        fmt.Println(i)
    }
}

func main() {
    wg.Add(1)
    go printNumbers()

    wg.Wait()
    fmt.Println("Main thread exits")
}

In the above code, ## The #printNumbers function is started as a thread and uses sync.WaitGroup to wait for the end of the thread. In the main function, add a waiting thread through wg.Add, and then start the printNumbers thread through the go keyword. Finally, wait for the thread to end through the wg.Wait function and output "Main thread exits".

4. Difference and summary

go keyword, and does not You need to explicitly wait for the coroutine to end; and when using threads, you need to use some synchronization mechanism (such as sync.WaitGroup) to wait for the thread to end. In addition, the creation and destruction overhead of coroutines is smaller and a large number of concurrent coroutines can be created; while the creation and destruction overhead of threads is greater and cannot be created on a large scale.

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