ThreadPool

Lightweight, Generic, Pure C++11 ThreadPool

Licensing

Public Domain. Use at your own risk for whatever you want. If your country doesn't have a public domain, feel free to say you found this on the side of the road.

Overview

ThreadPool is a super simple class that manages threads and jobs. threadCount threads are created at object instantiation time, and persist until the ThreadPool object is destroyed. You cannot change the thread count. Jobs are functions with no parameters or return values. This decision was to make it as generic as possible so it could be integrated into a variety of projects. If you can't get your job to work with those constraints, you're doing something wrong, or you need to roll your own ThreadPool. But you're probably making things overly complicated.

Below is a quick overview, but ThreadPool.h is documented, so just read that. It's less than 200 lines with comments.

class ThreadPool {
public:
    ThreadPool(int threadCount);
    ~ThreadPool();
    void AddJob(std::function<void(void)> job);
    void JoinAll();
    void WaitAll();
};

Examples

#include "ThreadPool.h"

#include <iostream>
#include <chrono>

int main() {
    ThreadPool pool(10); // Creates 10 threads.
    int JOB_COUNT = 100;
    
    for (int i = 0; i < JOB_COUNT; ++i)
        pool.AddJob([]() { 
            std::this_thread::sleep_for(std::chrono::seconds(1));
        });
    
    pool.JoinAll();
    std::cout << "Expected runtime: 10 seconds." << std::endl;
}

Convience Function for running a list of jobs in a pool, assuming the type being iterated is of std::function<void(void)>:

template <typename Iter>
void RunInPool(Iter begin, Iter end, int threadCount) {
    ThreadPool pool(threadCount);
    for( ; begin != end; begin = std::next(begin))
        pool.AddJob(*begin);
    pool.JoinAll();
}

It's worth nothing that pool.JoinAll(); is optional in this example, since JoinAll is invoked upon object deconstruction.