111 строки
4.1 KiB
Plaintext
111 строки
4.1 KiB
Plaintext
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.\" Copyright 2013 Los Alamos National Security, LLC. All rights reserved.
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.\" Copyright 2010 Cisco Systems, Inc. All rights reserved.
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.\" Copyright 2006-2008 Sun Microsystems, Inc.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.TH MPI_Neighbor_allgather 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.SH NAME
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\fBMPI_Neighbor_allgather\fP \- Gathers and distributes data from and to all neighbors
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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_Neighbor_allgather(void\fI *sendbuf\fP, int \fI sendcount\fP,
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MPI_Datatype\fI sendtype\fP, void\fI *recvbuf\fP, int\fI recvcount\fP,
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MPI_Datatype\fI recvtype\fP, MPI_Comm\fI comm\fP)
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.fi
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.SH Fortran Syntax
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.nf
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INCLUDE 'mpif.h'
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MPI_ALLGATHER(\fISENDBUF\fP,\fI SENDCOUNT\fP,\fI SENDTYPE\fP,\fI RECVBUF\fP,\fI RECVCOUNT\fP,\fI
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RECVTYPE\fP,\fI COMM\fP,\fI IERROR\fP)
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<type> \fISENDBUF\fP (*), \fIRECVBUF\fP (*)
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INTEGER \fISENDCOUNT\fP,\fI SENDTYPE\fP,\fI RECVCOUNT\fP,\fI RECVTYPE\fP,\fI COMM\fP,
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INTEGER \fIIERROR\fP
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.fi
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.SH INPUT PARAMETERS
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.ft R
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.TP 1i
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sendbuf
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Starting address of send buffer (choice).
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.TP 1i
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sendcount
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Number of elements in send buffer (integer).
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.TP 1i
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sendtype
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Datatype of send buffer elements (handle).
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.TP 1i
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recvbuf
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Starting address of recv buffer (choice).
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.TP 1i
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recvcount
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Number of elements received from any process (integer).
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.TP 1i
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recvtype
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Datatype of receive buffer elements (handle).
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.TP 1i
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comm
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Communicator (handle).
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.SH OUTPUT PARAMETERS
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.ft R
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.TP 1i
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recvbuf
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Address of receive buffer (choice).
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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_Neighbor_allgather is similar to MPI_Allgather, except that only the neighboring processes receive the result, instead of all processes. The neighbors and buffer layout is determined by the topology of \fIcomm\fP.
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.sp
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The type signature associated with sendcount, sendtype at a process must be equal to the type signature associated with recvcount, recvtype at any other process.
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.fi
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.sp
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.SH NEIGHBOR ORDERING
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For a distributed graph topology, created with MPI_Dist_graph_create, the sequence of neighbors
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in the send and receive buffers at each process is defined as the sequence returned by MPI_Dist_graph_neighbors
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for destinations and sources, respectively. For a general graph topology, created with MPI_Graph_create, the order of
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neighbors in the send and receive buffers is defined as the sequence of neighbors as returned by MPI_Graph_neighbors.
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Note that general graph topologies should generally be replaced by the distributed graph topologies.
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For a Cartesian topology, created with MPI_Cart_create, the sequence of neighbors in the send and receive
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buffers at each process is defined by order of the dimensions, first the neighbor in the negative direction
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and then in the positive direction with displacement 1. The numbers of sources and destinations in the
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communication routines are 2*ndims with ndims defined in MPI_Cart_create. If a neighbor does not exist, i.e., at
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the border of a Cartesian topology in the case of a non-periodic virtual grid dimension (i.e.,
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periods[...]==false), then this neighbor is defined to be MPI_PROC_NULL.
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If a neighbor in any of the functions is MPI_PROC_NULL, then the neighborhood collective communication behaves
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like a point-to-point communication with MPI_PROC_NULL in this direction. That is, the buffer is still part of
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the sequence of neighbors but it is neither communicated nor updated.
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.SH NOTES
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.sp
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The MPI_IN_PLACE option for \fIsendbuf\fP is not meaningful for this operation.
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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.
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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
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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_Neighbor_allgatherv
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MPI_Cart_create
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MPI_Garph_create
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MPI_Dist_graph_create
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.br
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MPI_Gather
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