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MPI_Finalize - Terminates MPI execution environment.
routine cleans up all MPI states. Once this routine is called, no MPI routine
(not even MPI_Init) may be called, except for MPI_Get_version, MPI_Initialized,
and MPI_Finalized. Unless there has been a call to MPI_Abort, you must ensure
that all pending communications involving a process are complete before
the process calls MPI_Finalize. If the call returns, each process may either
continue local computations or exit without participating in further communication
with other processes. At the moment when the last process calls MPI_Finalize,
all pending sends must be matched by a receive, and all pending receives
must be matched by a send.
- Fortran only: Error status (integer).
MPI_Finalize is collective over all connected
processes. If no processes were spawned, accepted, or connected, then this
means it is collective over MPI_COMM_WORLD. Otherwise, it is collective
over the union of all processes that have been and continue to be connected.
All processes must call this routine before exiting. All processes
will still exist but may not make any further MPI calls. MPI_Finalize guarantees
that all local actions required by communications the user has completed
will, in fact, occur before it returns. However, MPI_Finalize guarantees
nothing about pending communications that have not been completed; completion
is ensured only by MPI_Wait, MPI_Test, or MPI_Request_free combined with
some other verification of completion.
For example, a successful return
from a blocking communication operation or from MPI_Wait or MPI_Test means
that the communication is completed by the user and the buffer can be reused,
but does not guarantee that the local process has no more work to do. Similarly,
a successful return from MPI_Request_free with a request handle generated
by an MPI_Isend nullifies the handle but does not guarantee that the operation
has completed. The MPI_Isend is complete only when a matching receive has
If you would like to cause actions to happen when a process finishes,
attach an attribute to MPI_COMM_SELF with a callback function. Then, when
MPI_Finalize is called, it will first execute the equivalent of an MPI_Comm_free
on MPI_COMM_SELF. This will cause the delete callback function to be executed
on all keys associated with MPI_COMM_SELF in an arbitrary order. If no key
has been attached to MPI_COMM_SELF, then no callback is invoked. This freeing
of MPI_COMM_SELF happens before any other parts of MPI are affected. Calling
MPI_Finalized will thus return "false" in any of these callback functions.
Once you have done this with MPI_COMM_SELF, the results of MPI_Finalize
are not specified.
Almost all MPI routines return an error value;
C routines as the value of the function and Fortran routines in the last
argument. C++ functions do not return errors. If the default error handler
is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception
mechanism will be used to throw an MPI::Exception object.
Before the error
value is returned, the current MPI error handler is called. By default,
this error handler aborts the MPI job, except for I/O function errors. The
error handler may be changed with MPI_Comm_set_errhandler; the predefined
error handler MPI_ERRORS_RETURN may be used to cause error values to be
returned. Note that MPI does not guarantee that an MPI program can continue
past an error.
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