timer.h

#include <chrono>

class Timer {
 public:
  Timer() { start_ = std::chrono::high_resolution_clock::now(); }
  ~Timer() = default;

  template <typename T>
  uint64_t elapsed() {
    auto now = std::chrono::high_resolution_clock::now();
    return std::chrono::duration_cast<T>(now - start_).count();
  }
  uint64_t elapsed_us() { return elapsed<std::chrono::microseconds>(); }
  uint64_t elapsed_ms() { return elapsed<std::chrono::milliseconds>(); }

 private:
  std::chrono::time_point<std::chrono::high_resolution_clock> start_;
};