2.6 KiB
Name
MPI_Get_count - Gets the number of top-level elements received.
Syntax
C Syntax
#include <mpi.h>
int MPI_Get_count(const MPI_Status *status, MPI_Datatype datatype,
int *count)
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_GET_COUNT(STATUS, DATATYPE, COUNT, IERROR)
INTEGER STATUS(MPI_STATUS_SIZE), DATATYPE, COUNT, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Get_count(status, datatype, count, ierror)
TYPE(MPI_Status), INTENT(IN) :: status
TYPE(MPI_Datatype), INTENT(IN) :: datatype
INTEGER, INTENT(OUT) :: count
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Input Parameters
status: Return status of receive operation (status).datatype: Datatype of each receive buffer element (handle).
Output Parameters
count: Number of received elements (integer).IERROR: Fortran only: Error status (integer).
Description
Returns the number of entries received. (We count entries, each of type
datatype, not bytes.) The datatype argument should match the argument
provided by the receive call that set the status variable. (As explained
in Section 3.12.5 in the MPI-1 Standard, "Use of General Datatypes in
Communication," MPI_Get_count may, in certain situations, return the
value MPI_UNDEFINED.)
The datatype argument is passed to MPI_Get_count to improve performance.
A message might be received without counting the number of elements it
contains, and the count value is often not needed. Also, this allows the
same function to be used after a call to MPI_Probe.
Notes
If the size of the datatype is zero, this routine will return a count of
zero. If the amount of data in status is not an exact multiple of the
size of datatype (so that count would not be integral), a count of
MPI_UNDEFINED is returned instead.
Errors
If the value to be returned is larger than can fit into the count
parameter, an MPI_ERR_TRUNCATE error is raised.
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.
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.