Rank of the calling process in group, or MPI_UNDEFINED if the process is not a member (integer).
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.TP 1i
IERROR
Fortran only: Error status (integer).
.SH DESCRIPTION
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MPI_Group_rank returns as the output parameter \fIrank\fP the rank of the calling process in group. If the process is not a member of group then MPI_UNDEFINED is returned.
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.