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MPI_Wtime(3OpenMPI)                                                                      MPI_Wtime(3OpenMPI)



NAME
       MPI_Wtime - Returns an elapsed time on the calling processor.


SYNTAX
C Syntax
       #include <mpi.h>
       double MPI_Wtime()


Fortran Syntax
       INCLUDE 'mpif.h'
       DOUBLE PRECISION MPI_WTIME()


C++ Syntax
       #include <mpi.h>
       double Wtime()


RETURN VALUE
       Time in seconds since an arbitrary time in the past.


DESCRIPTION
       MPI_Wtime returns a floating-point number of seconds, representing elapsed wall-clock time since some
       time in the past.

       The "time in the past" is guaranteed not to change during the  life  of  the  process.  The  user  is
       responsible for converting large numbers of seconds to other units if they are preferred.

       This  function  is portable (it returns seconds, not "ticks"), it allows high resolution, and carries
       no unnecessary baggage. One would use it like this:

           {
              double starttime, endtime;
              starttime = MPI_Wtime();
               ....  stuff to be timed  ...
              endtime   = MPI_Wtime();
              printf("That took %f seconds\n",endtime-starttime);
           }

       The times returned are local to the node that called them. There is  no  requirement  that  different
       nodes return the "same" time.

NOTES
       The  boolean  variable  MPI_WTIME_IS_GLOBAL, a predefined attribute key that indicates whether clocks
       are synchronized, does not have a valid value in Open MPI, as the clocks are  not  guaranteed  to  be
       synchronized.


       This  is  intended  to  be a high-resolution, elapsed (or wall) clock. See MPI_Wtick to determine the
       resolution of MPI_Wtime.

       This function does not return an error value. Consequently, the result of calling it before  MPI_Init
       or after MPI_Finalize is undefined.


SEE ALSO
       MPI_Wtick




Open MPI 1.2                                   September 2006                            MPI_Wtime(3OpenMPI)