In-depth analysis of the similarities and differences between concurrency and parallelism in Go language

As an advanced programming language, Go language’s concurrency and parallel features are one of its greatest advantages. However, many people are not very clear about the concepts and differences between concurrency and parallelism in the Go language. This article will deeply analyze the similarities and differences between concurrency and parallelism in the Go language, and give specific code examples to illustrate.

1. The difference between concurrency and parallelism

1. Concurrency:

In the Go language, concurrency means that one program can process multiple Task. These tasks are not necessarily executed at the same time, but they can be called in time to improve the efficiency and performance of the program. In Go language, concurrency is achieved through goroutine. Goroutine is a lightweight thread in Go language that can execute tasks concurrently.

2. Parallel:

In the Go language, parallelism refers to truly executing multiple tasks simultaneously. These tasks are executed simultaneously on multiple processors to take full advantage of multi-core processors. In the Go language, parallelism is achieved by assigning multiple goroutines to different processors for execution.

2. Implementation of concurrency and parallelism

1. Concurrency implementation:

In Go language, use the keyword "go" to create goroutine, Thus achieving concurrency. The following is a simple concurrency example:

package main

import (
    "fmt"
    "time"
)

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

func main() {
    go printNumbers()
    
    for i := 1; i <= 5; i++ {
        fmt.Println("Main goroutine:", i)
        time.Sleep(1 * time.Second)
    }
}

In the above example, the printNumbers() function is put into a goroutine for concurrent execution. At the same time, the tasks in the main function are also executed in the main goroutine. Two tasks Can be done simultaneously.

2. Parallel implementation:

In the Go language, you can specify the number of goroutines executed in parallel by setting the GOMAXPROCS environment variable. The following is a simple parallel example:

package main

import (
    "fmt"
    "runtime"
    "time"
)

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

func main() {
    runtime.GOMAXPROCS(2) // 设置并行执行的goroutine数目为2

    go printNumbers()
    
    for i := 1; i <= 5; i++ {
        fmt.Println("Main goroutine:", i)
        time.Sleep(1 * time.Second)
    }
}

In the above example, by setting GOMAXPROCS to 2, two goroutines can be executed in parallel on two processors.

3. Summary

Through the above analysis and examples, we can see that the implementation of concurrency and parallelism in Go language is very simple and flexible. Concurrency is achieved through goroutine, which can execute multiple tasks simultaneously on a single processor; parallelism is achieved by setting the GOMAXPROCS environment variable, which can execute multiple tasks simultaneously on multiple processors. At the same time, concurrency and parallelism can be combined with each other to jointly improve the efficiency and performance of the program.

By deeply understanding the concepts and implementation of concurrency and parallelism in Go language, you can better utilize the features of Go language and improve program performance and efficiency. I hope this article will help readers understand concurrency and parallelism in the Go language.

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