How to make boost::thread_group execute a fixed number of parallel threads

Question

This is the code to create a thread_group and execute all threads in parallel:

boost::thread_group group;
for (int i = 0; i < 15; ++i)
    group.create_th         


        

Answer 1

I have something like this:

    boost::mutex mutex_;
    boost::condition_variable condition_;
    const size_t throttle_;
    size_t size_;
    bool wait_;
    template 
    void eval_(const Env &env, const F &f) {
        {   
            boost::unique_lock lock(mutex_);
            size_ = std::min(size_+1, throttle_);
            while (throttle_ <= size_) condition_.wait(lock);
        }
        f.eval(env);
        {
            boost::lock_guard lock(mutex_);
            --size_; 
        }
        condition_.notify_one();
    }