This manual page is for Mac OS X version 10.6

Reading manual pages

MPI_Buffer_detach(3OpenMPI)                                                      MPI_Buffer_detach(3OpenMPI)



NAME
       MPI_Buffer_detach - Removes an existing buffer (for use in MPI_Bsend, etc.)


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Buffer_detach(void *buf, int *size)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_BUFFER_DETACH(BUF, SIZE, IERROR)
            <type>    BUF(*)
            INTEGER   SIZE, IERROR


C++ Syntax
       #include <mpi.h>
       int Detach_buffer(void*& buffer)


OUTPUT PARAMETERS
       buf       Initial buffer address (choice).

       size      Buffer size, in bytes (integer).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       Detach  the  buffer  currently  associated with MPI. The call returns the address and the size of the
       detached buffer. This operation will block until all messages  currently  in  the  buffer  have  been
       transmitted.  Upon  return  of this function, the user may reuse or deallocate the space taken by the
       buffer.

       Example: Calls to attach and detach buffers.

           #define BUFFSIZE 10000
           int size
           char *buff;
           MPI_Buffer_attach( malloc(BUFFSIZE), BUFFSIZE);
           /* a buffer of 10000 bytes can now be used by MPI_Bsend */
           MPI_Buffer_detach( &buff, &size);
           /* Buffer size reduced to zero */
           MPI_Buffer_attach( buff, size);
           /* Buffer of 10000 bytes available again */


NOTES
       The reason that MPI_Buffer_detach returns the address and size of the buffer  being  detached  is  to
       allow nested libraries to replace and restore the buffer. For example, consider

           int size, mysize, idummy;
           void *ptr, *myptr, *dummy;
           MPI_Buffer_detach( &ptr, &size );
           MPI_Buffer_attach( myptr, mysize );
           ...
           ... library code ...
           ...
           MPI_Buffer_detach( &dummy, &idummy );
           MPI_Buffer_attach( ptr, size );

       This  is much like the action of the UNIX signal routine and has the same strengths (it's simple) and
       weaknesses (it only works for nested usages).

       For Fortran: The Fortran binding for this routine is different. Because Fortran does not have  point-ers, pointers,
       ers, it is impossible to provide a way to use the output of this routine to exchange buffers. In this
       case, only the size field is set.

       For C: Even though the buf argument is declared as void, it is really the address of a void  pointer.
       See Rationale, below, for more details.

       Even  though  the  C  functions MPI_Buffer_attach and MPI_Buffer_detach both have a first argument of
       type  void*,  these  arguments  are  used  differently:  A  pointer  to  the  buffer  is  passed   to
       MPI_Buffer_attach;  the  address of the pointer is passed to MPI_Buffer_detach, so that this call can
       return the pointer value.


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. If the default error handler is
       set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to  throw
       an MPI:Exception object.

       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_Buffer_attach
       MPI_Bsend



Open MPI 1.2                                   September 2006                    MPI_Buffer_detach(3OpenMPI)