131 lines
5.5 KiB
HTML
131 lines
5.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
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<HEAD>
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<META NAME="GENERATOR" CONTENT="DOCTEXT">
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<TITLE>MPI_Waitsome</TITLE>
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</HEAD>
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<BODY BGCOLOR="FFFFFF">
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<H1 id="MPI_Waitsome">MPI_Waitsome</H1>
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Waits for some given MPI Requests to complete
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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_Waitsome(int incount, MPI_Request array_of_requests[], int *outcount,
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int array_of_indices[], MPI_Status *array_of_statuses)
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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>incount </B> <DD> length of array_of_requests (non-negative integer)
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</DL>
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<P>
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<H2>Input/Output Parameters</H2>
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<DL>
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<DT><B>array_of_requests </B> <DD> array of requests (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>outcount </B> <DD> number of completed requests (integer)
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<DT><B>array_of_indices </B> <DD> array of indices of operations that completed (integer)
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<DT><B>array_of_statuses </B> <DD> array of status objects for operations that completed (Status)
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</DL>
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<P>
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<H2>Notes</H2>
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The array of indices are in the range <tt>0</tt> to <tt>incount - 1</tt> for C and
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in the range <tt>1</tt> to <tt>incount</tt> for Fortran.
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<P>
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Null requests are ignored; if all requests are null, then the routine
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returns with <tt>outcount</tt> set to <tt>MPI_UNDEFINED</tt>.
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<P>
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While it is possible to list a request handle more than once in the
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array_of_requests, such an action is considered erroneous and may cause the
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program to unexecpectedly terminate or produce incorrect results.
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<P>
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<tt>MPI_Waitsome</tt> provides an interface much like the Unix <tt>select</tt> or <tt>poll
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</tt>calls and, in a high qualilty implementation, indicates all of the requests
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that have completed when <tt>MPI_Waitsome</tt> is called.
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However, <tt>MPI_Waitsome</tt> only guarantees that at least one
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request has completed; there is no guarantee that <em>all</em> completed requests
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will be returned, or that the entries in <tt>array_of_indices</tt> will be in
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increasing order. Also, requests that are completed while <tt>MPI_Waitsome</tt> is
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executing may or may not be returned, depending on the timing of the
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completion of the message.
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<P>
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<H2>Notes on the MPI_Status argument</H2>
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<P>
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The <tt>MPI_ERROR</tt> field of the status return is only set if
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the return from the MPI routine is <tt>MPI_ERR_IN_STATUS</tt>. That error class
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is only returned by the routines that take an array of status arguments
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(<tt>MPI_Testall</tt>, <tt>MPI_Testsome</tt>, <tt>MPI_Waitall</tt>, and <tt>MPI_Waitsome</tt>). In
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all other cases, the value of the <tt>MPI_ERROR</tt> field in the status is
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unchanged. See section 3.2.5 in the MPI-1.1 specification for the
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exact text.
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<P>
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For send operations, the only use of status is for <tt>MPI_Test_cancelled</tt> or
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in the case that there is an error in one of the four routines that
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may return the error class <tt>MPI_ERR_IN_STATUS</tt>, in which case the
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<tt>MPI_ERROR</tt> field of status will be set. In that case, the value
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will be set to <tt>MPI_SUCCESS</tt> for any send or receive operation that completed
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successfully, or <tt>MPI_ERR_PENDING</tt> for any operation which has neither
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failed nor completed.
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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_ARG </B> <DD> Invalid argument. Some argument is invalid and is not
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identified by a specific error class (e.g., <tt>MPI_ERR_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_REQUEST </B> <DD> Invalid <tt>MPI_Request</tt>. Either null or, in the case of a
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<tt>MPI_Start</tt> or <tt>MPI_Startall</tt>, not a persistent request.
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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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