NAME¶
MPI_Finalize - Terminates MPI execution environment.
SYNTAX¶
C Syntax¶
#include <mpi.h>
int MPI_Finalize()
Fortran Syntax¶
INCLUDE 'mpif.h'
MPI_FINALIZE( IERROR)
INTEGER IERROR
C++ Syntax¶
#include <mpi.h>
void Finalize()
OUTPUT PARAMETER¶
- IERROR
- Fortran only: Error status (integer).
DESCRIPTION¶
This 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.
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.
NOTES¶
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 completed.
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.
ERRORS¶
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.