Explore the atomicity characteristics of Golang variable assignment

Exploring the atomicity of variable assignment in Golang

Introduction:
In concurrent programming, it is very important to ensure the atomicity of data. Atomicity refers to The operations on the same data are indivisible, either all of them are executed successfully, or none of them are executed. Golang provides some atomic operations, such as the atomic operation function in the atomic package, which can be used to ensure the atomicity of variable assignment operations.
This article will explore the atomicity of variable assignment in Golang, and demonstrate and verify it through specific code examples.

1. Atomic operation functions in Golang
Golang’s atomic package provides a series of atomic operation functions, the most commonly used ones are the following:

1. atomic.AddInt32 (&var, val): Atomically adds val to the value of var and returns the new value.
2. atomic.AddInt64(&var, val): Atomically adds val to the value of var and returns the new value.
3. atomic.AddUint32(&var, val): Atomically adds val to the value of var and returns the new value.
4. atomic.AddUint64(&var, val): Atomically adds val to the value of var and returns the new value.
5. atomic.LoadInt32(&var): Get the value of var atomically and return it.
6. atomic.LoadInt64(&var): Get the value of var atomically and return it.
7. atomic.LoadUint32(&var): Get the value of var atomically and return it.
8. atomic.LoadUint64(&var): Get the value of var atomically and return it.
9. atomic.StoreInt32(&var, val): Store val to var atomically.
10. atomic.StoreInt64(&var, val): Store val to var atomically.
11. atomic.StoreUint32(&var, val): Store val to var atomically.
12. atomic.StoreUint64(&var, val): Store val to var atomically.

2. Example of atomicity of variable assignment
The following uses a specific example to illustrate the atomicity of variable assignment.

package main

import (
    "fmt"
    "sync"
    "sync/atomic"
)

var (
    count int32
    wg    sync.WaitGroup
)

func increaseCount() {
    for i := 0; i < 10000; i++ {
        atomic.AddInt32(&count, 1)
    }
    wg.Done()
}

func main() {
    wg.Add(2)
    go increaseCount()
    go increaseCount()
    wg.Wait()
    fmt.Println("Count: ", count)
}

In the above code, a global variable count and a waiting group wg are defined. The increaseCount function implements the auto-increment operation on the count variable by using the atomic.AddInt32 function, increasing by 1 each time. In the main function, two goroutines are started to execute the increaseCount function. Each goroutine increments 10,000 times, and finally outputs the count value through fmt.Println.

Run the above code, the results are as follows:

Count: 20000

As you can see, due to the use of the atomic operation function atomic.AddInt32, the atomicity of the auto-increment operation on the count variable is guaranteed, and finally we get Correct result.

3. Example without atomicity guarantee
Let’s look at an example without atomicity guarantee.

package main

import (
    "fmt"
    "sync"
)

var (
    count int32
    wg    sync.WaitGroup
)

func increaseCount() {
    for i := 0; i < 10000; i++ {
        count += 1  // count的自增操作不是原子性的
    }
    wg.Done()
}

func main() {
    wg.Add(2)
    go increaseCount()
    go increaseCount()
    wg.Wait()
    fmt.Println("Count: ", count)
}

In the above code, the count = 1 operation in the increaseCount function is not atomic, so race conditions may occur during concurrent execution, resulting in incorrect results.

Run the above code, the results may appear as follows (the results may be different each time):

Count:  15923

As you can see, since the atomicity of the count auto-increment operation is not guaranteed, the final result is The result is wrong.

4. Conclusion
Through the above code examples, we can draw the following conclusions:

1. The atomic package in Golang provides some atomic operation functions that can be used to ensure Atomicity of variable assignment operations.
2. In concurrent programming, using atomic operation functions can avoid race conditions and ensure the correctness of data.

Summary:
When writing concurrent programs, in order to ensure the atomicity of data operations, we can use the atomic operation function in the atomic package provided by Golang. These functions can ensure that operations on shared variables are atomic, thereby avoiding the occurrence of race conditions and ensuring the correctness of data. Through the example code demonstration in this article, readers can have a deeper understanding of the atomicity of variable assignment in Golang, and rationally use atomic operation functions in actual development to improve the stability and performance of the program.

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