Go language multi-threaded operation implementation

introduction

Multithreading is a programming concept that allows the operating system to handle multiple tasks simultaneously. In a multi-threaded environment, each thread represents the execution process of a task. These threads can run simultaneously, allowing programs to make more efficient use of computing resources, especially in systems with multi-core processors.

1. How to implement multi-threading

1. Creation and management of threads:

The way threads are created and managed may vary in different programming languages. For example, in Java, it can be extended byThreadClass or implementationRunnableInterface to create threads. In Python, you can usethreadingModule to create threads.

2. Shared resources and synchronization:

A major challenge in multithreaded programs is managing access to shared resources. Race conditions may occur when multiple threads try to access the same resource at the same time (such as a variable or data structure).
To prevent this, synchronization mechanisms such as mutexes, semaphores, or other synchronization tools need to be used to ensure that only one thread can access specific resources at a time.

3. Inter-thread communication:

There is a need between threads to communicate and coordinate their work. This can be achieved through shared memory, events, message queues, etc.

4. Thread life cycle management:

The life cycle of a thread includes creation, execution, waiting (possible state, if the thread is waiting for certain resources or events) and terminating.
Effectively managing the life cycle of threads is crucial to prevent resource leakage and ensure program stability.

5. Thread safety:

When designing multithreaded programs, it is very important to ensure thread safety. This means that the code written is safe to execute in a multi-threaded environment without causing data corruption or inconsistency.

6. Consider concurrency issues:

In multi-threaded programming, special attention should be paid to concurrency problems, such as deadlock, hunger, live lock, etc. These issues often involve inappropriate synchronization between threads.

7. Performance and resource utilization:

Although multithreading can improve program performance, if used improperly, it can also lead to performance degradation. For example, too many threads may lead to too many context switches, which in turn reduces efficiency.

8. Tools and libraries for specific languages or frameworks:

Most modern programming languages provide rich libraries and frameworks to support multithreaded programming, such as Java'sPackage, Pythonasynciolibrary, etc.

2. Go language multi-threading

Go language has its own unique implementation and concept in terms of multi-threading, most importantly its "goroutine" and "channel". This approach from Go provides a lighter and easier to manage concurrency mechanism than traditional threads.

Goroutine

In Go, traditional threading models are not used directly, but concepts called "goroutine" are used. Goroutine is a lightweight thread managed by the Go runtime environment.

1. Lightweight:

Goroutines are lighter than traditional operating system threads, they take up less memory and start faster.
The Go runtime can schedule thousands of goroutines on very few operating system threads.

2. Dynamic stack:

Goroutines have dynamic stacks, which means their stack sizes can grow and shrink as needed, which is in contrast to fixed-size thread stacks.

3. Scheduling:

Goroutines are scheduled by the Go runtime scheduler, not directly scheduled by the operating system.
This scheduler runs in the user state and uses a technique called M:N scheduling (mapped multiple goroutines to fewer operating system threads).

Channel

Channel is the main way to communicate between goroutines in Go language. They provide a synchronization mechanism that allows goroutines to exchange data securely without explicit locks or conditional variables.

1. Data exchange:

Channels allows one goroutine to send data to another goroutine.

2. Synchronization:

Through the send and receive channels, goroutines can be synchronized.

3. Blocking and non-blocking:

Channels can be blocking or non-blocking. By default, send and receive operations block while waiting for the other end to be ready.

4. Buffered and non-buffered:

Channels can be non-buffered (unbuffered channel) or have a fixed-size buffer (buffered channel). The unbuffered channel ensures that there is a corresponding reception for each send.

Implementation principle

1. Goroutine scheduling:

Go uses a collaboration-based scheduling model, not preemptive. This means that the code actively "given out" control at certain points (such as I/O operations, channel operations, system calls, etc.).
The runtime maintains multiple threads (M) and multiplex goroutines (G) on these threads. It also uses a resource called P (processor) to maintain the local queue, which is used to schedule goroutines.

2. Work Stealing:

To balance the load, Go's scheduler uses the concept of work-stealing. The idle thread can steal goroutines from the busy thread to execute.

3. Creation and destruction of Goroutine:

Creating a goroutine is less expensive than creating a thread. When the goroutine is no longer needed, it will be automatically cleaned by the garbage collector.

4. The underlying implementation of Channel:

Channel implementation includes some synchronization primitives, such as mutexes and condition variables, as well as queues for storing data.

This concurrency model of Go is ideal for highly concurrency and network-intensive applications. It provides a relatively simple way to take advantage of the capabilities of multi-core processors while reducing the risk of complexity and errors when writing concurrent programs.

3. Use examples

Calculate the sum of integers using Goroutines and Channels

Suppose we want to calculate the sum of integers from 1 to 10. We divide this task into two parts, let the two goroutines calculate the sum of the part separately, and then pass the result back to the main goroutine for sum calculation.

package main

import (
    "fmt"
    "sync"
)

// Function that calculates the sum of partsfunc sum(numbers []int, ch chan int) {
    sum := 0
    for _, number := range numbers {
        sum += number
    }
    ch &lt;- sum // Send the result to the channel}

func main() {
    numbers := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
    
    // Create a channel for transferring results    ch := make(chan int)
    
    // Split the array and start two goroutines    go sum(numbers[:len(numbers)/2], ch)
    go sum(numbers[len(numbers)/2:], ch)
    
    // Read two results from the channel and calculate the sum    sum1, sum2 := &lt;-ch, &lt;-ch

    ("Total sum:", sum1 + sum2)
}

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