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<H1 id="MPI_Isend">MPI_Isend</H1>
Begins a nonblocking send
<H2>Synopsis</H2>
<PRE>
int MPI_Isend(const void *buf, int count, MPI_Datatype datatype, int dest, int tag,
MPI_Comm comm, MPI_Request * request)
</PRE>
<H2>Input Parameters</H2>
<DL>
<DT><B>buf </B> <DD> initial address of send buffer (choice)
<DT><B>count </B> <DD> number of elements in send buffer (integer)
<DT><B>datatype </B> <DD> datatype of each send buffer element (handle)
<DT><B>dest </B> <DD> rank of destination (integer)
<DT><B>tag </B> <DD> message tag (integer)
<DT><B>comm </B> <DD> communicator (handle)
</DL>
<P>
<H2>Output Parameters</H2>
<DL>
<DT><B>request </B> <DD> communication request (handle)
</DL>
<P>
<H2>Notes for Fortran</H2>
All MPI routines in Fortran (except for <tt>MPI_WTIME</tt> and <tt>MPI_WTICK</tt>) have
an additional argument <tt>ierr</tt> at the end of the argument list. <tt>ierr
</tt>is an integer and has the same meaning as the return value of the routine
in C. In Fortran, MPI routines are subroutines, and are invoked with the
<tt>call</tt> statement.
<P>
All MPI objects (e.g., <tt>MPI_Datatype</tt>, <tt>MPI_Comm</tt>) are of type <tt>INTEGER
</tt>in Fortran.
<P>
<H2>Errors</H2>
<P>
All MPI routines (except <tt>MPI_Wtime</tt> and <tt>MPI_Wtick</tt>) return an error value;
C routines as the value of the function and Fortran routines in the last
argument. Before the value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job. The error handler
may be changed with <tt>MPI_Comm_set_errhandler</tt> (for communicators),
<tt>MPI_File_set_errhandler</tt> (for files), and <tt>MPI_Win_set_errhandler</tt> (for
RMA windows). The MPI-1 routine <tt>MPI_Errhandler_set</tt> may be used but
its use is deprecated. The predefined error handler
<tt>MPI_ERRORS_RETURN</tt> may be used to cause error values to be returned.
Note that MPI does <em>not</em> guarentee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
possible.
<P>
<DL>
<DT><B>MPI_SUCCESS </B> <DD> No error; MPI routine completed successfully.
</DL>
<DL>
<DT><B>MPI_ERR_COMM </B> <DD> Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in <tt>MPI_Comm_rank</tt>).
</DL>
<DL>
<DT><B>MPI_ERR_COUNT </B> <DD> Invalid count argument. Count arguments must be
non-negative; a count of zero is often valid.
</DL>
<DL>
<DT><B>MPI_ERR_TYPE </B> <DD> Invalid datatype argument. Additionally, this error can
occur if an uncommitted MPI_Datatype (see <tt>MPI_Type_commit</tt>) is used
in a communication call.
</DL>
<DL>
<DT><B>MPI_ERR_TAG </B> <DD> Invalid tag argument. Tags must be non-negative; tags
in a receive (<tt>MPI_Recv</tt>, <tt>MPI_Irecv</tt>, <tt>MPI_Sendrecv</tt>, etc.) may
also be <tt>MPI_ANY_TAG</tt>. The largest tag value is available through the
the attribute <tt>MPI_TAG_UB</tt>.
</DL>
<DL>
<DT><B>MPI_ERR_RANK </B> <DD> Invalid source or destination rank. Ranks must be between
zero and the size of the communicator minus one; ranks in a receive
(<tt>MPI_Recv</tt>, <tt>MPI_Irecv</tt>, <tt>MPI_Sendrecv</tt>, etc.) may also be <tt>MPI_ANY_SOURCE</tt>.
</DL>
<DL>
<DT><B>MPI_ERR_INTERN </B> <DD> This error is returned when some part of the MPICH
implementation is unable to acquire memory.
</DL>
<P>
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