77 строки
2.6 KiB
Groff
77 строки
2.6 KiB
Groff
.\"Copyright 2006, Sun Microsystems, Inc.
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.\"Copyright (c) 1996 Thinking Machines
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.TH MPI_Buffer_attach 3OpenMPI "September 2006" "Open MPI 1.2" " "
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.SH NAME
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\fBMPI_Buffer_attach\fP \- Attaches a user-defined buffer for sending.
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.SH SYNTAX
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.ft R
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.SH C Syntax
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.nf
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#include <mpi.h>
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int MPI_Buffer_attach(void \fI*buf\fP, int\fI size\fP)
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.SH Fortran Syntax
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.nf
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INCLUDE 'mpif.h'
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MPI_BUFFER_ATTACH(\fIBUF\fP,\fI SIZE\fP, \fIIERROR\fP)
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<type> \fIBUF\fP(\fI*\fP)
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INTEGER \fISIZE\fP,\fI IERROR \fP
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.SH C++ Syntax
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.nf
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#include <mpi.h>
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void Attach_buffer(void* \fIbuffer\fP, int \fIsize\fP)
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.SH INPUT PARAMETERS
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.ft R
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.TP 1i
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buf
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Initial buffer address (choice).
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.TP 1i
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size
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Buffer size, in bytes (integer).
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.SH OUTPUT PARAMETER
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.ft R
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.TP 1i
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IERROR
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Fortran only: Error status (integer).
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.SH DESCRIPTION
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.ft R
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Provides to MPI a buffer in the user's memory to be used for buffering outgoing messages. The buffer is used only by messages sent in buffered mode. Only one buffer can be attached to a process at a time.
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.SH NOTES
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.ft R
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The size given should be the sum of the sizes of all outstanding Bsends that you intend to have, plus MPI_BSEND_OVERHEAD 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
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.sp
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.nf
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MPI_Buffer_attach( buf, size );
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MPI_Bsend( \&..., count=20, datatype=type1, \&... );
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\&...
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MPI_Bsend( \&..., count=40, datatype=type2, \&... );
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.fi
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.sp
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the value of size in the MPI_Buffer_attach call should be greater than the value computed by
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.sp
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.nf
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MPI_Pack_size( 20, type1, comm, &s1 );
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MPI_Pack_size( 40, type2, comm, &s2 );
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size = s1 + s2 + 2 * MPI_BSEND_OVERHEAD;
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.fi
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.sp
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MPI_BSEND_OVERHEAD gives the maximum amount of buffer space that may be used by the Bsend routines. This value is in mpi.h for C and mpif.h for Fortran.
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.SH ERRORS
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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.
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.sp
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Before the error value is returned, the current MPI error handler is
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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.
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.SH SEE ALSO
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.ft R
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.sp
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MPI_Buffer_detach
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