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<TITLE>MPI_Testsome</TITLE>
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MPI_Testsome
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Tests for some given requests to complete
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Synopsis
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int MPI_Testsome(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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Input Parameters
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incount length of array_of_requests (integer)
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array_of_requests array of requests (array of handles)
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Output Parameters
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outcount number of completed requests (integer)
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array_of_indices array of indices of operations that
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completed (array of integers)
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array_of_statuses array of status objects for
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operations that completed (array of Status). May be <tt>MPI_STATUSES_IGNORE</tt>.
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Notes
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While it is possible to list a request handle more than once in the
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<tt>array_of_requests</tt>, 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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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 <tt>malloc
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</tt>or other non-MPICH runtime routines that are themselves not interrupt-safe.
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Notes on the MPI_Status argument
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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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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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Notes for Fortran
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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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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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Errors
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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 not 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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MPI_SUCCESS No error; MPI routine completed successfully.
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MPI_ERR_IN_STATUS The actual error value is in the <tt>MPI_Status</tt> argument.
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This error class is returned only from the multiple-completion routines
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(<tt>MPI_Testall</tt>, <tt>MPI_Testany</tt>, <tt>MPI_Testsome</tt>, <tt>MPI_Waitall</tt>, <tt>MPI_Waitany</tt>,
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and <tt>MPI_Waitsome</tt>). The field <tt>MPI_ERROR</tt> in the status argument
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contains the error value or <tt>MPI_SUCCESS</tt> (no error and complete) or
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<tt>MPI_ERR_PENDING</tt> to indicate that the request has not completed.
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The MPI Standard does not specify what the result of the multiple
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completion routines is when an error occurs. For example, in an
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<tt>MPI_WAITALL</tt>, does the routine wait for all requests to either fail or
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complete, or does it return immediately (with the MPI definition of
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immediately, which means independent of actions of other MPI processes)?
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MPICH has chosen to make the return immediate (alternately, local in MPI
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terms), and to use the error class <tt>MPI_ERR_PENDING</tt> (introduced in MPI 1.1)
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to indicate which requests have not completed. In most cases, only
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one request with an error will be detected in each call to an MPI routine
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that tests multiple requests. The requests that have not been processed
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(because an error occured in one of the requests) will have their
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<tt>MPI_ERROR</tt> field marked with <tt>MPI_ERR_PENDING</tt>.
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