Timing

MPI defines a timer which is very convenient for performance debugging and which provides a portable timing facility.

MPI_WTIME()

Code            double MPI_Wtime(void)

MPI_WTIME returns a floating-point number of seconds, representing wall-clock time. To time a process, you can call MPI_WTIME just before the process starts, and again just after the process ends; then calculate the difference between the two times.