Synopsis

int MPI_Buffer_attach(void *buffer, int size)
int MPI_Buffer_attach_c(void *buffer, MPI_Count size)

Input Parameters

buffer

initial buffer address (choice)

size

buffer size, in bytes (non-negative integer)

Notes

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 MPI_Pack_size. 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).

NotThreadSafe

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 Fortran.

Errors

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 guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

  • MPI_SUCCESS - No error; MPI routine completed successfully.

  • MPI_ERR_ARG - Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., 'MPI_ERR_RANK').

  • MPI_ERR_OTHER - Other error; use 'MPI_Error_string' to get more information about this error code.

See also

MPI_Buffer_detach(3) MPI_Bsend(3)