Attaches a user-defined buffer for sending


#include "mpi.h"
int MPI_Buffer_attach( buffer, size )
void *buffer;
int  size;

Input Parameters

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 thatyou intend to have, plus a few hundred bytes 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 thanthe 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 inthe buffer for use by the BSEND routines in using the buffer. This valueis in mpi.h (for C) and mpif.h (for Fortran).

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) havean additional argument ierr at the end of the argument list. ierris an integer and has the same meaning as the return value of the routinein C. In Fortran, MPI routines are subroutines, and are invoked with thecall statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGERin Fortran.


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 lastargument. Before the value is returned, the current MPI error handler iscalled. By default, this error handler aborts the MPI job. The error handlermay be changed with MPI_Errhandler_set; the predefined error handlerMPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue pastan error.

No error; MPI routine completed successfully.
Invalid buffer pointer. Usually a null buffer where one is not valid.
An internal error has been detected. This is fatal. Please send a bug report to

See Also

MPI_Buffer_detach, MPI_Bsend