#include <iostream>
#include <syncstream>
#include <thread>

int main()
{
    std::jthread jthreads[std::thread::hardware_concurrency()];

    for (auto &t: jthreads)
        t = std::jthread([]
        {
            for (std::size_t i = 0; i < 10000; ++i)
                std::osyncstream(std::cout)
                    << "hola, soy " << std::this_thread::get_id() << '\n';
        });
}