MPI_BSEND(3)                       Open MPI                       MPI_BSEND(3)


MPI_Bsend -- Basic send with user-specified buffering.

SYNTAX
   C Syntax

          #include <mpi.h>

          int MPI_Bsend(const void *buf, int count, MPI_Datatype datatype,
             int dest, int tag, MPI_Comm comm)

   Fortran Syntax

          USE MPI
          ! or the older form: INCLUDE 'mpif.h'

          MPI_BSEND(BUF, COUNT,DATATYPE, DEST, TAG, COMM, IERROR)
              <type>  BUF(*)
              INTEGER COUNT, DATATYPE, DEST, TAG, COMM, IERROR

   Fortran 2008 Syntax

          USE mpi_f08
          MPI_Bsend(buf, count, datatype, dest, tag, comm, ierror)
              TYPE(*), DIMENSION(..), INTENT(IN) :: buf
              INTEGER, INTENT(IN) :: count, dest, tag
              TYPE(MPI_Datatype), INTENT(IN) :: datatype
              TYPE(MPI_Comm), INTENT(IN) :: comm
              INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

       o buf : Initial address of send buffer (choice).

       o count : Number of entries in send buffer (nonnegative integer).

       o datatype : Datatype of each send buffer element (handle).

       o dest : Rank of destination (integer).

       o tag : Message tag (integer).

       o comm : Communicator (handle).

OUTPUT PARAMETERS

       o ierror : Fortran only: Error status (integer).

DESCRIPTION
       MPI_Bsend performs a buffered-mode, blocking send.

NOTES
       This send is provided as a convenience function; it allows the user to
       send messages without worrying about where they are buffered (because
       the user must have provided buffer space with MPI_Buffer_attach).

       In deciding how much buffer space to allocate, remember that the buffer
       space is not available for reuse by subsequent MPI_Bsends unless you
       are certain that the message has been received (not just that it should
       have been received). For example, this code does not allocate enough
       buffer space:

          MPI_Buffer_attach( b, n*sizeof(double) + MPI_BSEND_OVERHEAD );
          for (i=0; i<m; i++) {
              MPI_Bsend( buf, n, MPI_DOUBLE, ... );
          }

       because only enough buffer space is provided for a single send, and the
       loop may start a second MPI_Bsend before the first is done making use
       of the buffer.

       In C, you can force the messages to be delivered by MPI_Buffer_detach(
       &b, &n ); MPI_Buffer_attach( b, n ); (The MPI_Buffer_detach will not
       complete until all buffered messages are delivered.)

ERRORS
       Almost all MPI routines return an error value; C routines as the return
       result of the function and Fortran routines in the last argument.

       Before the error value is returned, the current MPI error handler
       associated with the communication object (e.g., communicator, window,
       file) is called.  If no communication object is associated with the MPI
       call, then the call is considered attached to MPI_COMM_SELF and will
       call the associated MPI error handler. When MPI_COMM_SELF is not
       initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize,
       or when using the Sessions Model exclusively) the error raises the
       initial error handler. The initial error handler can be changed by
       calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World
       model, or the mpi_initial_errhandler CLI argument to mpiexec or info
       key to MPI_Comm_spawn/MPI_Comm_spawn_multiple.  If no other appropriate
       error handler has been set, then the MPI_ERRORS_RETURN error handler is
       called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is
       called for all other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       o MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI
         processes.

       o MPI_ERRORS_ABORT An error handler that can be invoked on a
         communicator, window, file, or session. When called on a
         communicator, it acts as if MPI_Abort was called on that
         communicator. If called on a window or file, acts as if MPI_Abort was
         called on a communicator containing the group of processes in the
         corresponding window or file. If called on a session, aborts only the
         local process.

       o MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by
       calling:

       o MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       o MPI_File_create_errhandler then MPI_File_set_errhandler

       o MPI_Session_create_errhandler then MPI_Session_set_errhandler or at
         MPI_Session_init

       o MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past
       an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more
       information.

COPYRIGHT
       2003-2024, The Open MPI Community

                                 April 8, 2024                    MPI_BSEND(3)