template <typename I, typename Lambda>
void CoLoop(I begin, I end, const Lambda& lambda)
{
	size_t chunk = max(size_t((end - begin) / CPU_Cores()), (size_t)1);
	CoWork co;
	while(begin < end) {
		co & [=] {
			lambda(begin, begin + min(chunk, size_t(end - begin)));
		};
		begin += chunk;
	}
}

template <class I, class Better>
I CoBest(I begin, I end, const Better& better)
{
	I best = begin++;
	CoLoop(begin, end,
		[=, &best](I i, I e) {
			I b = i++;
			while(i < e) {
				if(better(*i, *b))
					b = i;
				i++;
			}
			CoWork::FinLock(); // better is shared across threads, needs a lock!
			if(better(*b, *best))
				best = b;
		}
	);
	return best;
}