Concurrent partition

main.cpp

// Given
const auto size = ...;
auto begin = ...;

std::list<std::future<void>> futures;
const auto concurrency = std::thread::hardware_concurrency();
const auto partition = std::imaxdiv(size, concurrency);
for (int i{}; i < concurrency; ++i) {
  const auto end = begin + partition.quot + (i < partition.rem);
  futures.emplace_back(std::async([this, begin, end]() {
    for (auto i = begin; i != end; ++i) {
      // Do something with i
    }
  }));
  begin = end;
}