93 lines
4.0 KiB
HTML
93 lines
4.0 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
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<META NAME="GENERATOR" CONTENT="DOCTEXT">
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<TITLE>MPI_Alltoallv</TITLE>
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<BODY BGCOLOR="FFFFFF">
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<A NAME="MPI_Alltoallv"><H1>MPI_Alltoallv</H1></A>
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Sends data from all to all processes; each process may send a different amount of data and provide displacements for the input and output data.
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<H2>Synopsis</H2>
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<PRE>
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int MPI_Alltoallv(const void *sendbuf, const int *sendcounts,
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const int *sdispls, MPI_Datatype sendtype, void *recvbuf,
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const int *recvcounts, const int *rdispls, MPI_Datatype recvtype, MPI_Comm comm)
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</PRE>
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<H2>Input Parameters</H2>
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<DL>
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<DT><B>sendbuf </B><DD>starting address of send buffer (choice)
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<DT><B>sendcounts </B><DD>integer array equal to the group size
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specifying the number of elements to send to each processor
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<DT><B>sdispls </B><DD>integer array (of length group size). Entry
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<TT>j</TT> specifies the displacement (relative to sendbuf from
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which to take the outgoing data destined for process <TT>j
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</TT>
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<DT><B>sendtype </B><DD>data type of send buffer elements (handle)
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<DT><B>recvcounts </B><DD>integer array equal to the group size
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specifying the maximum number of elements that can be received from
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each processor
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<DT><B>rdispls </B><DD>integer array (of length group size). Entry
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<TT>i</TT> specifies the displacement (relative to recvbuf at
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which to place the incoming data from process <TT>i
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</TT>
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<DT><B>recvtype </B><DD>data type of receive buffer elements (handle)
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<DT><B>comm </B><DD>communicator (handle)
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</DL>
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<P>
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<H2>Output Parameters</H2>
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<DL><DT><B>recvbuf </B> <DD> address of receive buffer (choice)
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</DL>
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<P>
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<H2>Thread and Interrupt Safety</H2>
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<P>
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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 <TT>malloc
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</TT>or other non-MPICH runtime routines that are themselves not interrupt-safe.
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<P>
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<H2>Notes for Fortran</H2>
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All MPI routines in Fortran (except for <TT>MPI_WTIME</TT> and <TT>MPI_WTICK</TT>) have
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an additional argument <TT>ierr</TT> at the end of the argument list. <TT>ierr
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</TT>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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<TT>call</TT> statement.
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<P>
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All MPI objects (e.g., <TT>MPI_Datatype</TT>, <TT>MPI_Comm</TT>) are of type <TT>INTEGER
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</TT>in Fortran.
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<P>
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<H2>Errors</H2>
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<P>
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All MPI routines (except <TT>MPI_Wtime</TT> and <TT>MPI_Wtick</TT>) 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 <TT>MPI_Comm_set_errhandler</TT> (for communicators),
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<TT>MPI_File_set_errhandler</TT> (for files), and <TT>MPI_Win_set_errhandler</TT> (for
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RMA windows). The MPI-1 routine <TT>MPI_Errhandler_set</TT> may be used but
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its use is deprecated. The predefined error handler
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<TT>MPI_ERRORS_RETURN</TT> may be used to cause error values to be returned.
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Note that MPI does <EM>not</EM> 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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<P>
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<DL><DT><B>MPI_ERR_COMM </B> <DD> Invalid communicator. A common error is to use a null
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communicator in a call (not even allowed in <TT>MPI_Comm_rank</TT>).
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</DL>
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<DL><DT><B>MPI_ERR_COUNT </B> <DD> Invalid count argument. Count arguments must be
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non-negative; a count of zero is often valid.
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</DL>
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<DL><DT><B>MPI_ERR_TYPE </B> <DD> Invalid datatype argument. Additionally, this error can
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occur if an uncommitted MPI_Datatype (see <TT>MPI_Type_commit</TT>) is used
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in a communication call.
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</DL>
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<DL><DT><B>MPI_ERR_BUFFER </B> <DD> Invalid buffer pointer. Usually a null buffer where
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one is not valid.
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</DL>
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