Concurrency implementation in golang language

Golang is a programming language developed by Google for server-side applications. It has the characteristics of powerful concurrency performance, so it has been increasingly widely used in distributed systems and large-scale high-concurrency application development. This article mainly introduces the implementation of concurrency in Golang language.

1. Concurrency and Parallelism

Before talking about Golang’s concurrency implementation, we need to understand the two concepts of concurrency and parallelism. Concurrency refers to the ability to perform multiple tasks at the same time, possibly within the same program. Parallelism refers to the ability to perform multiple tasks simultaneously. The realization of concurrency requires the help of threads, processes and other mechanisms of the operating system, while parallelism requires the help of hardware capabilities such as multi-core CPUs. Simply put, Golang's concurrency is implemented in a single thread, and parallelism is implemented in multiple threads.

2. Golang’s concurrency model

Golang’s concurrency model is based on the two concepts of Goroutine and Channel. Goroutine is a lightweight thread provided by Golang, which is implemented based on coroutine. Compared with threads, the overhead of creating and destroying Goroutines is very small, and the overhead of switching between Goroutines is also very small. Therefore, a large number of Goroutines can be opened to perform tasks, thereby improving the concurrency performance of the application.

As important as Goroutine is Channel. Channel is a thread-safe communication mechanism provided by Golang. Through Channel, Goroutines can communicate and coordinate execution to achieve data sharing and collaborative work, while also avoiding problems such as competition that may occur when multi-threads are concurrent.

3. How to create and call Goroutine

Goroutine can be created and called using the go keyword. The following is a simple example:

func main() {
    go func() {
        fmt.Println("This is a Goroutine!")
    }()
    fmt.Println("This is the main function!")
    time.Sleep(time.Second)
}

In the above example, we used the go keyword to create a Goroutine. Functions in Goroutine are implemented using anonymous functions. Before outputting the string "This is a Goroutine!", the program will first output the string "This is the main function!". Since Goroutine is executed asynchronously, the application does not wait for the execution of Goroutine, but exits directly. We can use the Sleep function in the time package to make the thread wait for a certain period of time so that Goroutine has time to execute.

4. The use of Channel

Channel is a thread-safe communication mechanism provided by Golang. It can be used to synchronize information and share data between Goroutines to prevent competition issues between multiple Goroutines.

Using Channel is very simple. First we need to create a Channel. Creating a Channel requires specifying the type of elements in the Channel. The following is an example of creating a Channel:

ch := make(chan int)

In this example, we use the make function to create a Channel with int type elements.

To send data to the Channel, you can call the send method of the Channel (using the <-operator), as shown below:

ch <- 10

In this example, we send an int type to the Channel Data 10. If the Channel is full, the operation is blocked until there is space in the Channel.

To receive data from Channel, you can call Channel's receive method (using <-operator), as shown below:

n := <-ch

In this example, we received an int type from Channel Data n. If the Channel is empty, the operation will also be blocked until there is data in the Channel.

Channel also has other operations, such as the close method to close the Channel, the len function to get the number of elements in the Channel, etc.

5. Golang Concurrent Programming Example

Below we use a simple example to demonstrate Golang’s concurrency implementation.

Suppose we need to calculate the average of all elements in an array. Due to the large number of elements in the array, the calculation may be time-consuming. We can use Golang's concurrency mechanism to speed up calculations.

First, we define an array a containing 100 elements of type int. Then we create 10 Goroutines to calculate the value of each element in an array, and finally add the sum of all elements and divide by the number of elements to get the average.

func main() {
    a := make([]int, 100)
    for i := 0; i < len(a); i++ {
        a[i] = i
    }

    count := 10
    resultChan := make(chan int, count)
    chunkSize := len(a) / count

    for i := 0; i < count; i++ {
        startIndex := i * chunkSize
        endIndex := (i + 1) * chunkSize
        if i == count-1 {
            endIndex = len(a)
        }
        go sumChunk(a[startIndex:endIndex], resultChan)
    }

    total := 0
    for i := 0; i < count; i++ {
        total += <-resultChan
    }

    fmt.Println("Average value of array is: ", float32(total)/float32(len(a)))
}

func sumChunk(chunk []int, resultChan chan int) {
    sum := 0
    for _, v := range chunk {
        sum += v
    }
    resultChan <- sum
}

In this example, we define an int type array a with a length of 100. For an array a of length len(a), we create count (here 10) Goroutines to calculate the sum of all elements in the array a. Each Goroutine calculates the sum of a subsequence of array a and sends its result to resultChan. Finally, we receive the results of each Goroutine from resultChan and add them together to get the sum of all elements and calculate the average of all elements.

In practice, we usually set the number of Goroutines according to calculation needs. If multiple cores of the CPU can be utilized, we can set the number of Goroutines to the number of CPU cores. Otherwise, we need to set the number of Goroutines as needed to use CPU resources reasonably. When there are too many Goroutines, the system may have problems such as context switching, resulting in performance degradation.

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