File: MPI_Buffer_attach.3

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.TH MPI_Buffer_attach 3 "1/6/1997" " " "MPI"
.SH NAME
MPI_Buffer_attach \-  Attaches a user-defined buffer for sending 
.SH SYNOPSIS
.nf
#include "mpi.h"
int MPI_Buffer_attach( buffer, size )
void *buffer;
int  size;
.fi
.SH INPUT PARAMETERS
.PD 0
.TP
.B buffer 
- initial buffer address (choice) 
.PD 1
.PD 0
.TP
.B size 
- buffer size, in bytes (integer) 
.PD 1

.SH NOTES
The size given should be the sum of the sizes of all outstanding Bsends that
you intend to have, plus a few hundred bytes for each Bsend that you do.
For the purposes of calculating size, you should use 
.I MPI_Pack_size
.
In other words, in the code
.nf
MPI_Buffer_attach( buffer, size );
MPI_Bsend( ..., count=20, datatype=type1,  ... );
...
MPI_Bsend( ..., count=40, datatype=type2, ... );
.fi
the value of 
.I size
in the MPI_Buffer_attach call should be greater than
the value computed by
.nf
MPI_Pack_size( 20, type1, comm, &s1 );
MPI_Pack_size( 40, type2, comm, &s2 );
size = s1 + s2 + 2 * MPI_BSEND_OVERHEAD;
.fi
The 
.I 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 
.I mpi.h
(for C) and 
.I mpif.h
(for Fortran).

.SH NOTES FOR FORTRAN
All MPI routines in Fortran (except for 
.I MPI_WTIME
and 
.I MPI_WTICK
) have
an additional argument 
.I ierr
at the end of the argument list.  
.I 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
.I call
statement.

All MPI objects (e.g., 
.I MPI_Datatype
, 
.I MPI_Comm
) are of type 
.I INTEGER
in Fortran.

.SH ERRORS

All MPI routines (except 
.I MPI_Wtime
and 
.I 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 
.I MPI_Errhandler_set
; the predefined error handler
.I MPI_ERRORS_RETURN
may be used to cause error values to be returned.
Note that MPI does 
.B not
guarentee that an MPI program can continue past
an error.

.PD 0
.TP
.B MPI_SUCCESS 
- No error; MPI routine completed successfully.
.PD 1
.PD 0
.TP
.B MPI_ERR_BUFFER 
- Invalid buffer pointer.  Usually a null buffer where
one is not valid.
.PD 1
.PD 0
.TP
.B MPI_ERR_INTERN 
- An internal error has been detected.  This is fatal.
Please send a bug report to 
.I mpi-bugs@mcs.anl.gov
.
.PD 1

.SH SEE ALSO
MPI_Buffer_detach, MPI_Bsend
.br
.SH LOCATION
bufattach.c