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.TH MPI_Neighbor_allgather 3 "11/12/2019" " " "MPI"
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.SH NAME
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MPI_Neighbor_allgather \- In this function, each process i gathers data items from each process j if an edge (j,i) exists in the topology graph, and each process i sends the same data items to all processes j where an edge (i,j) exists. The send buffer is sent to each neighboring process and the l-th block in the receive buffer is received from the l-th neighbor.
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.SH SYNOPSIS
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.nf
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int MPI_Neighbor_allgather(const void *sendbuf, int sendcount, MPI_Datatype sendtype, void *recvbuf,
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int recvcount, MPI_Datatype recvtype, MPI_Comm comm)
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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 sendbuf
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- starting address of the send buffer (choice)
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.PD 1
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.PD 0
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.TP
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.B sendcount
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- number of elements sent to each neighbor (non-negative integer)
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.PD 1
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.PD 0
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.TP
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.B sendtype
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- data type of send buffer elements (handle)
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.PD 1
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.PD 0
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.TP
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.B recvcount
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- number of elements received from each neighbor (non-negative integer)
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.PD 1
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.PD 0
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.TP
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.B recvtype
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- data type of receive buffer elements (handle)
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.PD 1
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.PD 0
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.TP
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.B comm
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- communicator (handle)
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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 recvbuf
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- starting address of the receive buffer (choice)
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.PD 1
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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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guarentee 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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