135 lines
4.7 KiB
HTML
135 lines
4.7 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="DOCTEXT">
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<TITLE>MPI_Allgatherv</TITLE>
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</HEAD>
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<BODY BGCOLOR="FFFFFF">
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<H1 id="MPI_Allgatherv">MPI_Allgatherv</H1>
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Gathers data from all tasks and deliver the combined data to all tasks
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<H2>Synopsis</H2>
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<PRE>
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</PRE>
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<PRE>
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int MPI_Allgatherv(const void *sendbuf, int sendcount, MPI_Datatype sendtype,
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void *recvbuf, const int recvcounts[], const int displs[],
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MPI_Datatype recvtype, MPI_Comm comm)
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</PRE>
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<PRE>
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int MPI_Allgatherv_c(const void *sendbuf, MPI_Count sendcount,
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MPI_Datatype sendtype, void *recvbuf,
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const MPI_Count recvcounts[], const MPI_Aint displs[],
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MPI_Datatype recvtype, MPI_Comm comm)
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</PRE>
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<P>
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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>sendcount </B> <DD> number of elements in send buffer (non-negative integer)
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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> non-negative integer array (of length group size) containing the number of elements that are received from each process (non-negative integer)
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<DT><B>displs </B> <DD> integer array (of length group size). Entry i specifies the displacement (relative to recvbuf) at which to place the incoming data from process i (integer)
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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>
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<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>Notes</H2>
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The MPI standard (1.0 and 1.1) says that
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<br>
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<P>
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<br>
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<P>
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The jth block of data sent from
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each process is received by every process and placed in the jth block of the
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buffer <tt>recvbuf</tt>.
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<br>
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<P>
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<br>
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<P>
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This is misleading; a better description is
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<br>
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<P>
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<br>
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<P>
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The block of data sent from the jth process is received by every
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process and placed in the jth block of the buffer <tt>recvbuf</tt>.
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<br>
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<P>
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<br>
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<P>
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This text was suggested by Rajeev Thakur, and has been adopted as a
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clarification to the MPI standard by the MPI-Forum.
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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> 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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<P>
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<DL>
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<DT><B>MPI_SUCCESS </B> <DD> No error; MPI routine completed successfully.
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</DL>
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<DL>
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<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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<DL>
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<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>
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<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>
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<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>
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<DT><B>MPI_ERR_OTHER </B> <DD> Other error; use <tt>MPI_Error_string</tt> to get more information
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about this error code.
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</DL>
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<P>
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</BODY></HTML>
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