CPU and GPU timing code

timer.h

#pragma once

namespace util {

  struct gpu_timer {
  #ifdef __CUDACC__
    gpu_timer() {
      cudaEventCreate(&m_start);
      cudaEventCreate(&m_end);
      cudaEventRecord(m_start, 0);
    }

    float milliseconds_elapsed() {
      float elapsed_time;
      cudaEventRecord(m_end, 0);
      cudaEventSynchronize(m_end);
      cudaEventElapsedTime(&elapsed_time, m_start, m_end);
      return elapsed_time;
    }

    float seconds_elapsed() {
      return milliseconds_elapsed() / 1000.0;
    }

  protected:
    cudaEvent_t m_start, m_end;
  #endif // __CUDACC__
  };

  struct cpu_timer {
    public:
      cpu_timer() {
        t1 = ClockGetTime();
      }

      double nanoseconds_elapsed() {
        t2 = ClockGetTime();
        return diff(t1, t2).tv_sec * 1000000000LL + diff(t1, t2).tv_nsec;
      }
      
      double microseconds_elapsed() {
        return nanoseconds_elapsed() / 1000.0;
      }

      double milliseconds_elapsed() {
        return microseconds_elapsed() / 1000.0;
      }

      double seconds_elapsed() {
        return milliseconds_elapsed() / 1000.0;
      }

    protected:
      timespec diff(timespec start, timespec end) {
        timespec temp;
        if ((end.tv_nsec-start.tv_nsec)<0) {
          temp.tv_sec = end.tv_sec-start.tv_sec-1;
          temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
        } else {
          temp.tv_sec = end.tv_sec-start.tv_sec;
          temp.tv_nsec = end.tv_nsec-start.tv_nsec;
        }
        return temp;
      }

      // Nano second precision CPU clock
      timespec ClockGetTime() {
        timespec ts;
        clock_gettime(CLOCK_REALTIME, &ts);
        return ts; //(uint64_t)ts.tv_sec * 1000000000LL + (uint64_t)ts.tv_nsec;
      }

    protected:
      timespec t1, t2;
  };
} // namespace util