Time in seconds since an arbitrary time in the past.
.SH DESCRIPTION
.ft R
MPI_Wtime returns a floating-point number of seconds, representing elapsed wall-clock time since some time in the past.
.PP
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.
.PP
This function is portable (it returns seconds, not "ticks"), it allows high resolution, and carries no unnecessary baggage. One would use it like this:
.sp
.nf
{
double starttime, endtime;
starttime = MPI_Wtime();
\&.... stuff to be timed \&...
endtime = MPI_Wtime();
printf("That took %f seconds\\n",endtime-starttime);
}
.fi
.PP
The times returned are local to the node that called them. There is no requirement that different nodes return the "same" time.
.SH 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.
