#include <iostream>
#include <thread>
#include <vector>
#include <numeric>
#include <future>
#include <algorithm>
 
int sum(const int * a, const int * b)
{
        std::cout << std::this_thread::get_id() << '\n';
 
        auto distance = b-a;
        if(distance < 5) // willkuerliche Grenze
                return std::accumulate(a,b,0);
 
        const int * half = a + distance/2;
 
        auto fut_left = std::async(sum, a, half);
        auto right = sum(half, b);
 
        return fut_left.get() + right;
}
 
int main()
{
        std::vector<int> vec(256);
        std::iota(vec.begin(), vec.end(), 0);
        std::cout << sum(vec.data(), vec.data()+256) << '\n';
}
 

I2luY2x1ZGUgPGlvc3RyZWFtPgojaW5jbHVkZSA8dGhyZWFkPgojaW5jbHVkZSA8dmVjdG9yPgojaW5jbHVkZSA8bnVtZXJpYz4KI2luY2x1ZGUgPGZ1dHVyZT4KI2luY2x1ZGUgPGFsZ29yaXRobT4KCmludCBzdW0oY29uc3QgaW50ICogYSwgY29uc3QgaW50ICogYikKewogICAgICAgIHN0ZDo6Y291dCA8PCBzdGQ6OnRoaXNfdGhyZWFkOjpnZXRfaWQoKSA8PCAnXG4nOwoKICAgICAgICBhdXRvIGRpc3RhbmNlID0gYi1hOwogICAgICAgIGlmKGRpc3RhbmNlIDwgNSkgLy8gd2lsbGt1ZXJsaWNoZSBHcmVuemUKICAgICAgICAgICAgICAgIHJldHVybiBzdGQ6OmFjY3VtdWxhdGUoYSxiLDApOwoKICAgICAgICBjb25zdCBpbnQgKiBoYWxmID0gYSArIGRpc3RhbmNlLzI7CgogICAgICAgIGF1dG8gZnV0X2xlZnQgPSBzdGQ6OmFzeW5jKHN1bSwgYSwgaGFsZik7CiAgICAgICAgYXV0byByaWdodCA9IHN1bShoYWxmLCBiKTsKCiAgICAgICAgcmV0dXJuIGZ1dF9sZWZ0LmdldCgpICsgcmlnaHQ7Cn0KCmludCBtYWluKCkKewogICAgICAgIHN0ZDo6dmVjdG9yPGludD4gdmVjKDI1Nik7CiAgICAgICAgc3RkOjppb3RhKHZlYy5iZWdpbigpLCB2ZWMuZW5kKCksIDApOwogICAgICAgIHN0ZDo6Y291dCA8PCBzdW0odmVjLmRhdGEoKSwgdmVjLmRhdGEoKSsyNTYpIDw8ICdcbic7Cn0K