Parallel sort algorithm not used when calling with poolstl::par

Hello, Adam. Thank you for awesome library.

Maybe I'm something doing wrong... I've simple code, something like

#include <poolstl/poolstl.hpp>
#include <vector>
#include <cassert>

int main() {
    std::vector<int> v(40 * 1024 * 1024, 0);
    v.front() = 100;
    v.back() = -1;
    std::sort(poolstl::par, v.begin(), v.end(), std::less());
    assert(v.front() < v.back());
}

And it utilizes only one core.

Ubuntu 22.04, gcc 12.3.0