76 строки
2.9 KiB
Plaintext
76 строки
2.9 KiB
Plaintext
.\" -*- nroff -*-
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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_Cart_sub 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.SH NAME
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\fBMPI_Cart_sub \fP \- Partitions a communicator into subgroups, which form lower-dimensional Cartesian subgrids.
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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_Cart_sub(MPI_Comm \fIcomm\fP, const int\fI remain_dims\fP[], MPI_Comm\fI *comm_new\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_CART_SUB(\fICOMM, REMAIN_DIMS, COMM_NEW, IERROR\fP)
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INTEGER \fICOMM, COMM_NEW, IERROR\fP
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LOGICAL \fIREMAIN_DIMS\fP(*)
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.fi
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.SH C++ Syntax
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.nf
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#include <mpi.h>
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Cartcomm Cartcomm::Sub(const bool \fIremain_dims\fP[]) const
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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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comm
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Communicator with Cartesian structure (handle).
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.TP 1i
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remain_dims
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The ith entry of remain_dims specifies whether the ith dimension is kept in the subgrid (true) or is dropped (false) (logical vector).
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.SH OUTPUT PARAMETERS
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.ft R
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.TP 1i
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comm_new
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Communicator containing the subgrid that includes the calling process (handle).
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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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If a Cartesian topology has been created with MPI_Cart_create, the function MPI_Cart_sub can be used to partition the communicator group into subgroups that form lower-dimensional Cartesian subgrids, and to build for each subgroup a communicator with the associated subgrid Cartesian topology. (This function is closely related to MPI_Comm_split.)
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.sp
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\fBExample:\fP Assume that MPI_Cart_create( \&..., comm) has defined a (2 x 3 x 4) grid. Let remain_dims = (true, false, true). Then a call to
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.sp
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.nf
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MPI_Cart_sub(comm, remain_dims, comm_new)
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.fi
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.sp
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will create three communicators, each with eight processes in a 2 x 4 Cartesian topology. If remain_dims = (false, false, true) then the call to MPI_Cart_sub(comm, remain_dims, comm_new) will create six nonoverlapping communicators, each with four processes, in a one-dimensional Cartesian topology.
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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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.nf
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MPI_Cart_create
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MPI_Comm_split
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