MPI_Wtime(3) MPI MPI_Wtime(3)NAME
MPI_Wtime - Returns an elapsed time on the calling processor
SYNOPSIS
double MPI_Wtime( void )
RETURN VALUE
Time in seconds since an arbitrary time in the past.
NOTES
This is intended to be a high-resolution, elapsed (or wall) clock. See MPI_WTICK to determine the resolution of MPI_WTIME .
If the attribute MPI_WTIME_IS_GLOBAL is defined and true, then the value is synchronized across all processes in MPI_COMM_WORLD .
NOTES FOR FORTRAN
This is a function, declared as DOUBLE PRECISION MPI_WTIME() in Fortran.
SEE ALSO
also: MPI_Wtick, MPI_Comm_get_attr, MPI_Attr_get
LOCATION
wtime.c
11/6/2008 MPI_Wtime(3)
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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
",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)
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