187 lines
3.9 KiB
Groff
187 lines
3.9 KiB
Groff
.TH MPI_Intercomm_create 3 "2/3/2025" " " "MPI"
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.SH NAME
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MPI_Intercomm_create \- Creates an intercommuncator from two intracommunicators
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.SH SYNOPSIS
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.nf
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.fi
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.nf
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int MPI_Intercomm_create(MPI_Comm local_comm, int local_leader,
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MPI_Comm peer_comm, int remote_leader, int tag,
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MPI_Comm *newintercomm)
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.fi
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.SH INPUT PARAMETERS
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.PD 0
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.TP
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.B local_comm
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- local intra-communicator (handle)
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.PD 1
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.PD 0
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.TP
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.B local_leader
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- rank of local group leader in local_comm (integer)
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.PD 1
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.PD 0
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.TP
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.B peer_comm
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- `peer communicator; significant only at the local_leader (handle)
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.PD 1
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.PD 0
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.TP
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.B remote_leader
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- rank of remote group leader in peer_comm; significant only at the local_leader (integer)
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.PD 1
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.PD 0
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.TP
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.B tag
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- tag (integer)
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.PD 1
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.SH OUTPUT PARAMETERS
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.PD 0
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.TP
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.B newintercomm
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- new inter-communicator (handle)
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.PD 1
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.SH NOTES
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.I peer_comm
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is significant only for the process designated the
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.I local_leader
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in the
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.I local_comm
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\&.
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The MPI 1.1 Standard contains two mutually exclusive comments on the
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input intercommunicators. One says that their respective groups must be
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disjoint; the other that the leaders can be the same process. After
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some discussion by the MPI Forum, it has been decided that the groups must
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be disjoint. Note that the
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.B reason
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given for this in the standard is
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.B not
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the reason for this choice; rather, the
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.B other
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operations on
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intercommunicators (like
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.I MPI_Intercomm_merge
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) do not make sense if the
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groups are not disjoint.
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.SH THREAD AND INTERRUPT SAFETY
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This routine is thread-safe. This means that this routine may be
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safely used by multiple threads without the need for any user-provided
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thread locks. However, the routine is not interrupt safe. Typically,
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this is due to the use of memory allocation routines such as
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.I malloc
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or other non-MPICH runtime routines that are themselves not interrupt-safe.
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.SH NOTES FOR FORTRAN
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All MPI routines in Fortran (except for
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.I MPI_WTIME
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and
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.I MPI_WTICK
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) have
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an additional argument
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.I ierr
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at the end of the argument list.
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.I ierr
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is an integer and has the same meaning as the return value of the routine
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in C. In Fortran, MPI routines are subroutines, and are invoked with the
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.I call
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statement.
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All MPI objects (e.g.,
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.I MPI_Datatype
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,
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.I MPI_Comm
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) are of type
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.I INTEGER
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in Fortran.
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.SH ERRORS
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All MPI routines (except
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.I MPI_Wtime
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and
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.I MPI_Wtick
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) return an error value;
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C routines as the value of the function and Fortran routines in the last
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argument. Before the value is returned, the current MPI error handler is
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called. By default, this error handler aborts the MPI job. The error handler
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may be changed with
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.I MPI_Comm_set_errhandler
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(for communicators),
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.I MPI_File_set_errhandler
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(for files), and
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.I MPI_Win_set_errhandler
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(for
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RMA windows). The MPI-1 routine
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.I MPI_Errhandler_set
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may be used but
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its use is deprecated. The predefined error handler
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.I MPI_ERRORS_RETURN
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may be used to cause error values to be returned.
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Note that MPI does
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.B not
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guarantee that an MPI program can continue past
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an error; however, MPI implementations will attempt to continue whenever
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possible.
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.PD 0
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.TP
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.B MPI_SUCCESS
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- No error; MPI routine completed successfully.
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.PD 1
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.PD 0
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.TP
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.B MPI_ERR_ARG
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- Invalid argument. Some argument is invalid and is not
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identified by a specific error class (e.g.,
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.I MPI_ERR_RANK
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).
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.PD 1
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.PD 0
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.TP
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.B MPI_ERR_COMM
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- Invalid communicator. A common error is to use a null
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communicator in a call (not even allowed in
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.I MPI_Comm_rank
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).
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.PD 1
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.PD 0
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.TP
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.B MPI_ERR_TAG
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- Invalid tag argument. Tags must be non-negative; tags
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in a receive (
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.I MPI_Recv
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,
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.I MPI_Irecv
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,
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.I MPI_Sendrecv
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, etc.) may
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also be
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.I MPI_ANY_TAG
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\&.
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The largest tag value is available through the
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the attribute
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.I MPI_TAG_UB
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\&.
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.PD 1
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.PD 0
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.TP
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.B MPI_ERR_OTHER
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- Other error; use
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.I MPI_Error_string
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to get more information
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about this error code.
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.PD 1
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.SH SEE ALSO
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MPI_Intercomm_merge, MPI_Comm_free, MPI_Comm_remote_group, MPI_Comm_remote_size
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.br
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