Blocking receive for a message
int MPI_Recv(void *buf, int count, MPI_Datatype datatype, int source, int tag,
MPI_Comm comm, MPI_Status * status)
- initial address of receive buffer (choice)
- status object (Status)
- maximum number of elements in receive buffer (integer)
- datatype of each receive buffer element (handle)
- rank of source (integer)
- message tag (integer)
- communicator (handle)
The count argument indicates the maximum length of a message; the actual
length of the message can be determined with MPI_Get_count.
Thread and Interrupt Safety
This routine is thread-safe. This means that this routine may be
safely used by multiple threads without the need for any user-provided
thread locks. However, the routine is not interrupt safe. Typically,
this is due to the use of memory allocation routines such as malloc
or other non-MPICH runtime routines that are themselves not interrupt-safe.
Notes for Fortran
All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have
an additional argument ierr at the end of the argument list. ierr
is an integer and has the same meaning as the return value of the routine
in C. In Fortran, MPI routines are subroutines, and are invoked with the
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER
The status argument must be declared as an array of size MPI_STATUS_SIZE,
as in integer status(MPI_STATUS_SIZE).
All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value;
C routines as the value of the function and Fortran routines in the last
argument. Before the value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job. The error handler
may be changed with MPI_Comm_set_errhandler (for communicators),
MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for
RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but
its use is deprecated. The predefined error handler
MPI_ERRORS_RETURN may be used to cause error values to be returned.
Note that MPI does not guarentee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
- No error; MPI routine completed successfully.
- Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in MPI_Comm_rank).
- Invalid datatype argument. Additionally, this error can
occur if an uncommitted MPI_Datatype (see MPI_Type_commit) is used
in a communication call.
- Invalid count argument. Count arguments must be
non-negative; a count of zero is often valid.
- Invalid tag argument. Tags must be non-negative; tags
in a receive (MPI_Recv, MPI_Irecv, MPI_Sendrecv, etc.) may
also be MPI_ANY_TAG. The largest tag value is available through the
the attribute MPI_TAG_UB.
- Invalid source or destination rank. Ranks must be between
zero and the size of the communicator minus one; ranks in a receive
(MPI_Recv, MPI_Irecv, MPI_Sendrecv, etc.) may also be MPI_ANY_SOURCE.