NAME

       MPI_Improbe - Non-blocking matched probe for a message.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Improbe(int source, int tag, MPI_Comm comm,
            int *flag, MPI_Message *message, MPI_Status *status)

Fortran Syntax

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_IMPROBE(SOURCE, TAG, COMM, FLAG, MESSAGE, STATUS, IERROR)
            LOGICAL   FLAG
            INTEGER   SOURCE, TAG, COMM, MESSAGE
            INTEGER   STATUS(MPI_STATUS_SIZE), IERROR

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Improbe(source, tag, comm, flag, message, status, ierror)
            INTEGER, INTENT(IN) :: source, tag
            TYPE(MPI_Comm), INTENT(IN) :: comm
            INTEGER, INTENT(OUT) :: flag
            TYPE(MPI_Message), INTENT(OUT) :: message
            TYPE(MPI_Status) :: status
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

       There is no C++ binding for this function.

INPUT PARAMETERS

       source    Source rank or MPI_ANY_SOURCE (integer).

       tag       Tag value or MPI_ANY_TAG (integer).

       comm      Communicator (handle).

OUTPUT PARAMETERS

       flag      Flag (logical).

       message   Message (handle).

       status    Status object (status).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       Like  MPI_Probe  and  MPI_Iprobe, the MPI_Mprobe and MPI_Improbe operations allow incoming messages to be
       queried without actually receiving them, except that MPI_Mprobe and MPI_Improbe provide  a  mechanism  to
       receive  the  specific  message  that  was  matched  regardless  of  other  intervening  probe or receive
       operations.  This gives the application an opportunity to decide how to receive the message, based on the
       information returned by the probe.  In particular, the application may allocate memory  for  the  receive
       buffer according to the length of the probed message.

       A matching probe with MPI_PROC_NULL as source returns flag = true, message = MPI_MESSAGE_NO_PROC, and the
       status object returns source = MPI_PROC_NULL, tag = MPI_ANY_TAG, and count = 0.

       MPI_Iprobe  returns a true value in flag if a message has been matched and can be received by passing the
       message handle to the MPI_Mrecv or MPI_Imrecv functions, provided the source was not MPI_PROC_NULL.

NOTE

       This is an MPI-3 function and has no C++ binding.

ERRORS

       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.

       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.

SEE ALSO

       MPI_Mprobe
       MPI_Probe
       MPI_Iprobe
       MPI_Mrecv
       MPI_Imrecv
       MPI_Cancel

4.1.6                                             Sep 30, 2023                                    MPI_Improbe(3)