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MPI_Buffer_attach(3) MPI MPI_Buffer_attach(3)
MPI_Buffer_attach - Attaches a user-provided buffer for sending
int MPI_Buffer_attach(void *buffer, int size)
buffer - initial buffer address (choice)
size - buffer size, in bytes (integer)
The size given should be the sum of the sizes of all outstanding Bsends
that you intend to have, plus MPI_BSEND_OVERHEAD for each Bsend that
you do. For the purposes of calculating size, you should use
In other words, in the code
MPI_Buffer_attach( buffer, size );
MPI_Bsend( ..., count=20, datatype=type1, ... );
MPI_Bsend( ..., count=40, datatype=type2, ... );
the value of size in the MPI_Buffer_attach call should be greater than
the value computed by
MPI_Pack_size( 20, type1, comm, &s1 );
MPI_Pack_size( 40, type2, comm, &s2 );
size = s1 + s2 + 2 * MPI_BSEND_OVERHEAD;
The MPI_BSEND_OVERHEAD gives the maximum amount of space that may be
used in the buffer for use by the BSEND routines in using the buffer.
This value is in mpi.h (for C) and mpif.h (for Fortran).
THREAD AND INTERRUPT SAFETY
The user is responsible for ensuring that multiple threads do not try
to update the same MPI object from different threads. This routine
should not be used from within a signal handler.
The MPI standard defined a thread-safe interface but this does not mean
that all routines may be called without any thread locks. For example,
two threads must not attempt to change the contents of the same
MPI_Info object concurrently. The user is responsible in this case for
using some mechanism, such as thread locks, to ensure that only one
thread at a time makes use of this routine. Because the buffer for
buffered sends (e.g., MPI_Bsend ) is shared by all threads in a
process, the user is responsible for ensuring that only one thread at a
time calls this routine or MPI_Buffer_detach .
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 call statement.
All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
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 possible.
- No error; MPI routine completed successfully.
- Invalid buffer pointer. Usually a null buffer where one is
- An internal error has been detected. This is fatal. Please
send a bug report to firstname.lastname@example.org .