Newsgroups: comp.parallel.mpi From: Erik Demaine Subject: Re: Timing problem Organization: University of Waterloo Date: Wed, 5 Mar 1997 13:32:14 GMT Message-ID: Eric Salo wrote: : > Is the time returned by MPI_Wtime() the cpu-time used by the program : > or is only the time elapsed since some time in the past ? : It measures wall-clock time, starting from some implementation-defined : starting point. Unless you are timing serial programs, wall-clock time is the only time that makes sense. Otherwise, message passing is timed completely incorrectly. Unfortunately, this depends on machine load. If you *really* want CPU time (serial application), you can use getrusage() or clock() or other facility of your OS. Cheers! Erik -- Erik Demaine () e-mail: eddemain@daisy.uwaterloo.ca Dept. of Computer Science || URL: http://daisy.uwaterloo.ca/~eddemain/ University of Waterloo || PGP key: finger me. "Maturity is switching Waterloo, ON Canada N2L 3G1 () from passive voice to active voice" -P. Alder