Apprendre Thread Pools and std::async | Advanced Concurrency Techniques

Definition

Thread Pool is a collection of pre-created threads that can execute multiple tasks efficiently without repeatedly creating and destroying threads. It improves performance by reusing threads and managing system resources effectively.

Thread pools are a foundational pattern in concurrent programming. Instead of spawning a new thread for each task—which is costly—a thread pool keeps a fixed number of threads alive and reuses them to handle incoming work. This approach reduces overhead, improves CPU utilization, and prevents excessive thread creation.

C++ simplifies asynchronous programming with std::async, which automatically handles task execution. Depending on the launch policy, it may run a task in a new thread or defer it until needed. While not a true thread pool, std::async provides a simple and effective way to run multiple tasks concurrently and collect their results using std::future.

main.cpp


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#include <iostream>
#include <future>
#include <vector>
#include <chrono>

// Simulate a time-consuming computation
int compute_square(int x)
{
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
    return x * x;
}

int main()
{
    std::vector<std::future<int>> futures;

    // Launch several asynchronous tasks
    for (int i = 1; i <= 5; ++i)
        futures.push_back(std::async(std::launch::async, compute_square, i));

    // Retrieve and print results
    for (int i = 0; i < futures.size(); ++i)
    {
        int result = futures[i].get();
        std::cout << "Square of " << (i + 1) << " is " << result << std::endl;
    }
}

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Section 3. Chapitre 1

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Definition

main.cpp


              123456789101112131415161718192021222324252627
            
#include <iostream>
#include <future>
#include <vector>
#include <chrono>

// Simulate a time-consuming computation
int compute_square(int x)
{
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
    return x * x;
}

int main()
{
    std::vector<std::future<int>> futures;

    // Launch several asynchronous tasks
    for (int i = 1; i <= 5; ++i)
        futures.push_back(std::async(std::launch::async, compute_square, i));

    // Retrieve and print results
    for (int i = 0; i < futures.size(); ++i)
    {
        int result = futures[i].get();
        std::cout << "Square of " << (i + 1) << " is " << result << std::endl;
    }
}

Tout était clair ?

Merci pour vos commentaires !

Section 3. Chapitre 1