106 строки
3.2 KiB
Groff
106 строки
3.2 KiB
Groff
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.\"Copyright 2006, Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.TH MPI_Bsend 3OpenMPI "September 2006" "Open MPI 1.2" " "
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.SH NAME
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\fBMPI_Bsend\fP \- Basic send with user-specified buffering.
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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_Bsend(void \fI*buf\fP, int\fI count\fP, MPI_Datatype\fI datatype\fP,
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int\fI dest\fP, int\fI tag\fP, MPI_Comm\fI comm\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_BSEND(\fIBUF\fP,\fI COUNT\fP,\fIDATATYPE\fP,\fI DEST\fP,\fI TAG\fP,\fI COMM\fP,\fI IERROR\fP)
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<type> \fIBUF\fP(*)
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INTEGER \fICOUNT\fP,\fI DATATYPE\fP,\fI DEST\fP,\fI TAG\fP,\fI COMM\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 Comm::Bsend(const void* \fIbuf\fP, int \fIcount\fP, const
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Datatype& \fIdatatype\fP, int \fIdest\fP, int \fItag\fP) const
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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 address of send buffer (choice).
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.TP 1i
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count
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Number of entries in send buffer (nonnegative integer).
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.TP 1i
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datatype
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Datatype of each send buffer element (handle).
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.TP 1i
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dest
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Rank of destination (integer).
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.TP 1i
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tag
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Message tag (integer).
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.TP 1i
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comm
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Communicator (handle).
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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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MPI_Bsend performs a buffered-mode, blocking send.
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.SH NOTES
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.ft R
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This send is provided as a convenience function; it allows the user to send messages without worrying about where they are buffered (because the user must have provided buffer space with MPI_Buffer_attach).
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.sp
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In deciding how much buffer space to allocate, remember that the buffer space
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is not available for reuse by subsequent \fIMPI_Bsend\fPs unless you are certain
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that the message
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has been received (not just that it should have been received). For example,
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this code does not allocate enough buffer space:
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.nf
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MPI_Buffer_attach( b, n*sizeof(double) + MPI_BSEND_OVERHEAD );
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for (i=0; i<m; i++) {
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MPI_Bsend( buf, n, MPI_DOUBLE, ... );
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}
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.fi
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because only enough buffer space is provided for a single send, and the
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loop may start a second
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.I MPI_Bsend
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before the first is done making use of the
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buffer.
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In C, you can
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force the messages to be delivered by
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MPI_Buffer_detach( &b, &n );
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MPI_Buffer_attach( b, n );
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(The
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.I MPI_Buffer_detach
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will not complete until all buffered messages are
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delivered.)
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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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.nf
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MPI_Buffer_attach
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MPI_Ibsend
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MPI_Bsend_init
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' @(#)MPI_Bsend.3 1.20 06/03/09
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