229 lines
6.5 KiB
Groff
229 lines
6.5 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "MPI_BUFFER_DETACH" "3" "Feb 14, 2025" "" "Open MPI"
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.in \\n[rst2man-indent\\n[rst2man-indent-level]]u
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..
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.sp
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\fI\%MPI_Buffer_detach\fP — Removes an existing buffer (for use in in \fI\%MPI_Bsend\fP,
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etc.)
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.SH SYNTAX
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.SS C Syntax
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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#include <mpi.h>
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int MPI_Buffer_detach(void *buf, int *size)
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SS Fortran Syntax
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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USE MPI
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! or the older form: INCLUDE \(aqmpif.h\(aq
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MPI_BUFFER_DETACH(BUF, SIZE, IERROR)
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<type> BUF(*)
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INTEGER SIZE, IERROR
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SS Fortran 2008 Syntax
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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USE mpi_f08
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MPI_Buffer_detach(buffer_addr, size, ierror)
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USE, INTRINSIC :: ISO_C_BINDING, ONLY
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TYPE(C_PTR), INTENT(OUT) :: buffer_addr
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INTEGER, INTENT(OUT) :: size
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INTEGER, OPTIONAL, INTENT(OUT) :: ierror
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SH OUTPUT PARAMETERS
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.INDENT 0.0
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.IP \(bu 2
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\fBbuf\fP : Initial buffer address (choice).
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.IP \(bu 2
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\fBsize\fP : Buffer size, in bytes (integer).
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.IP \(bu 2
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\fBierror\fP : Fortran only: Error status (integer).
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.UNINDENT
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.SH DESCRIPTION
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.sp
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Detach the buffer currently associated with MPI. The call returns the
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address and the size of the detached buffer. This operation will block
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until all messages currently in the buffer have been transmitted. Upon
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return of this function, the user may reuse or deallocate the space
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taken by the buffer.
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.sp
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Example: Calls to attach and detach buffers.
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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#define BUFFSIZE 10000
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int size char *buff;
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MPI_Buffer_attach( malloc(BUFFSIZE), BUFFSIZE);
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// a buffer of 10000 bytes can now be used by MPI_Bsend
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MPI_Buffer_detach( &buff, &size); // Buffer size reduced to zero
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MPI_Buffer_attach( buff, size); // Buffer of 10000 bytes available again
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SH NOTES
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.sp
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The reason that \fI\%MPI_Buffer_detach\fP returns the address and size of the
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buffer being detached is to allow nested libraries to replace and
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restore the buffer. For example, consider
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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int size, mysize, idummy;
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void *ptr, *myptr, *dummy;
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MPI_Buffer_detach( &ptr, &size );
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MPI_Buffer_attach( myptr, mysize );
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/* ... library code ... */
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MPI_Buffer_detach( &dummy, &idummy );
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MPI_Buffer_attach( ptr, size );
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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This is much like the action of the UNIX signal routine and has the same
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strengths (it’s simple) and weak‐nesses (it only works for nested
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usages).
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.sp
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For Fortran: The Fortran binding for this routine is different. Because
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Fortran does not have pointers, it is impossible to provide a way to use
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the output of this routine to exchange buffers. In this case, only the
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size field is set.
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.sp
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For C: Even though the buf argument is declared as void, it is really
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the address of a void pointer. See Rationale, below, for more details.
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.sp
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Even though the C functions \fI\%MPI_Buffer_attach\fP and \fI\%MPI_Buffer_detach\fP both
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have a first argument of type void*, these arguments are used
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differently: A pointer to the buffer is passed to \fI\%MPI_Buffer_attach\fP; the
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address of the pointer is passed to \fI\%MPI_Buffer_detach\fP, so that this call
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can return the pointer value.
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.SH ERRORS
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.sp
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Almost all MPI routines return an error value; C routines as the return result
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of the function and Fortran routines in the last argument.
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.sp
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Before the error value is returned, the current MPI error handler associated
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with the communication object (e.g., communicator, window, file) is called.
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If no communication object is associated with the MPI call, then the call is
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considered attached to MPI_COMM_SELF and will call the associated MPI error
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handler. When MPI_COMM_SELF is not initialized (i.e., before
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\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
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Model exclusively) the error raises the initial error handler. The initial
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error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
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MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
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argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
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If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
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error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error
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handler is called for all other MPI functions.
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.sp
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Open MPI includes three predefined error handlers that can be used:
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.INDENT 0.0
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.IP \(bu 2
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\fBMPI_ERRORS_ARE_FATAL\fP
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Causes the program to abort all connected MPI processes.
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.IP \(bu 2
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\fBMPI_ERRORS_ABORT\fP
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An error handler that can be invoked on a communicator,
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window, file, or session. When called on a communicator, it
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acts as if \fI\%MPI_Abort\fP was called on that communicator. If
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called on a window or file, acts as if \fI\%MPI_Abort\fP was called
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on a communicator containing the group of processes in the
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corresponding window or file. If called on a session,
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aborts only the local process.
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.IP \(bu 2
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\fBMPI_ERRORS_RETURN\fP
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Returns an error code to the application.
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.UNINDENT
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.sp
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MPI applications can also implement their own error handlers by calling:
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.INDENT 0.0
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.IP \(bu 2
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\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
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.IP \(bu 2
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\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
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.IP \(bu 2
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\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
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.IP \(bu 2
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\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
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.UNINDENT
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.sp
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Note that MPI does not guarantee that an MPI program can continue past
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an error.
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.sp
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See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
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.sp
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See the Error Handling section of the MPI\-3.1 standard for
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more information.
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.sp
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\fBSEE ALSO:\fP
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.INDENT 0.0
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.INDENT 3.5
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.INDENT 0.0
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.IP \(bu 2
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\fI\%MPI_Buffer_attach\fP
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.UNINDENT
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.UNINDENT
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.UNINDENT
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.SH COPYRIGHT
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2003-2025, The Open MPI Community
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.\" Generated by docutils manpage writer.
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.
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