How about this as a compromise solution: we add a close(), clear() or
destroy() function to each class that has a collective destructor. If a
user runs in parallel and has not manually cleaned up by calling
close/clear/destroy, we print a warning message from the destructor.
We can add options to turn the message off in parallel, or to turn it
on in serial (for users who want to check that their serial code is
ready to run in parallel), or to turn it on only from Python.
Garth
On Tue, 7 Oct, 2014 at 3:20 PM, Martin Sandve Alnæs
<[email protected]> wrote:
On 7 October 2014 15:58, Jed Brown <[email protected]> wrote:
>
> "Garth N. Wells" <[email protected]> writes:
> > I thought the issue we're discussing is that the above Python
pattern,
> > which is the natural way to do things, can break in parallel
because of
> > non-deterministic garbage collection and that we need an
alternative?
>
> The with statement (PEP 343) provides __exit__, which is
deterministic.
> That pattern is idiomatic and correct. Relying on garbage
collection
> when a variable falls out of scope is the problem.
Exactly. This includes the three patterns which are everywhere in
dolfin tests and demos:
File(...) << u
def f():
file = File(...)
file << u
def g():
file = File(...)
file << u
del file
(And as Jed said I was of course wrong about RAII providing exception
safety in the MPI context).
Martin
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