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<TITLE>MPI_Request_free</TITLE>
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MPI_Request_free
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Frees a communication request object
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Synopsis
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int MPI_Request_free(MPI_Request * request)
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Input Parameters
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request communication request (handle)
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Notes
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This routine is normally used to free inactive persistent requests created with
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either <tt>MPI_Recv_init</tt> or <tt>MPI_Send_init</tt> and friends. It is also
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permissible to free an active request. However, once freed, the request can no
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longer be used in a wait or test routine (e.g., <tt>MPI_Wait</tt>) to determine
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completion.
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This routine may also be used to free a non-persistent requests such as those
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created with <tt>MPI_Irecv</tt> or <tt>MPI_Isend</tt> and friends. Like active persistent
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requests, once freed, the request can no longer be used with test/wait routines
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to determine completion.
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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 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_REQUEST 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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MPI_ERR_ARG 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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See Also
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also: MPI_Isend, MPI_Irecv, MPI_Issend, MPI_Ibsend, MPI_Irsend,
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MPI_Recv_init, MPI_Send_init, MPI_Ssend_init, MPI_Rsend_init, MPI_Wait,
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MPI_Test, MPI_Waitall, MPI_Waitany, MPI_Waitsome, MPI_Testall, MPI_Testany,
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MPI_Testsome
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