56 lines
2.1 KiB
Groff
56 lines
2.1 KiB
Groff
.\" -*- nroff -*-
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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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.\" $COPYRIGHT$
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.TH MPI_Comm_rank 3 "Mar 26, 2019" "4.0.1" "Open MPI"
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.SH NAME
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\fBMPI_Comm_rank\fP \- Determines the rank of the calling process in the communicator.
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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_Comm_rank(MPI_Comm \fIcomm\fP, int\fI *rank\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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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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rank
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Rank of the calling process in group of comm (integer).
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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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This function gives the rank of the process in the
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particular communicator's group. It is equivalent to accessing the
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communicator's group with MPI_Comm_group, computing the rank using MPI_Group_rank, and then freeing the temporary group via MPI_Group_free.
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.sp
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Many programs will be written with the master-slave model, where one process (such as the rank-zero process) will play a supervisory role, and the other processes will serve as compute nodes. In this framework, MPI_Comm_size and MPI_Comm_rank are useful for determining the roles of the various processes of a communicator.
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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_Comm_group
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MPI_Comm_size
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MPI_Comm_compare
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