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MPI_Get_count - Gets the number of top-level elements received.
#include <mpi.h>
int MPI_Get_count(MPI_Status *status, MPI_Datatype datatype,
int *count)
INCLUDE ’mpif.h’
MPI_GET_COUNT(STATUS, DATATYPE, COUNT, IERROR)
INTEGER STATUS(MPI_STATUS_SIZE), DATATYPE, COUNT, IERROR
#include <mpi.h>
int Status::Get_count(const Datatype& datatype) const
- status
- Return status of receive operation (status).
- datatype
- Datatype of each receive buffer element (handle).
- count
- Number of received elements (integer).
- IERROR
- Fortran only: Error status
(integer).
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.
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.
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.
MPI_Get_elements
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