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#ifndef MO2_THREAD_UTILS_H
#define MO2_THREAD_UTILS_H
#include <mutex>
#include <thread>
namespace MOShared {
/**
* @brief Apply the given callable to each element between the two given iterators
* in a parallel way.
*
* The callable should be independent, or properly synchronized, and the source of
* the range should not change during this call.
*
* @param start Beginning of the range.
* @param end End of the range.
* @param callable Callable to apply to every element of the range. See std::invoke
* requirements. Must be copiable.
* @param nThreads Number of threads to use.
*
*/
template <class It, class Callable>
void parallelMap(It begin, It end, Callable callable, std::size_t nThreads)
{
std::mutex m;
std::vector<std::thread> threads(nThreads);
// Create the thread:
// - The mutex is only used to fetch/increment the iterator.
// - The callable is copied in each thread to avoid conflicts.
for (auto &thread: threads) {
thread = std::thread([&m, &begin, end, callable]() {
while (true) {
decltype(begin) it;
{
std::scoped_lock lock(m);
if (begin == end) {
break;
}
it = begin++;
}
if (it != end) {
std::invoke(callable, *it);
}
}
});
}
// Join everything:
for (auto& t : threads) {
t.join();
}
}
}
#endif
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