Comment 16 for bug 1083720

I had to revert the change I did yesterday, we cannot make test/trial
functions with different counts than -1/-2 without breaking a lot of code.
In particular, it won't work with test/trial functions in different spaces.
So we're back to square one, and the conclusion is that these fixed counts
are evil, but that can't be fixed with more index trickery.

On 29 November 2012 13:22, Johan Hake <email address hidden> wrote:

> On 11/28/2012 08:58 PM, Joachim Haga wrote:
> >>> Will the circular references "functionspace <->
> >>> testfunction" be a problem for garbage collection?
> >>
> >> Yes.
> >
> > I am not familiar with the particulars here, but the circular
> > references are only a problem if the objects have custom deleters
> > (__del__ methods). Swig likes to generate (empty) __del__ methods, but
> > they can be disabled by the should-have-been-default flag
> > --noproxydel.
>
> Ok, nice to know. Also see:
>
> http://stackoverflow.com/questions/2428301/should-i-worry-about-
> circular-references-in-python
>
> for some nice references.
>
> It also seems like none of the classes implements __del__ so in theory
> we should be fine. The thread above do mention possible slowness in
> performance in these type of garbage collections, but I guess that would
> be for larger chain of circular references?
>
> You could also use weak refs I guess, or just implement the test/trial
> count discussed later in the thread.
>
> Johan
>
> > -j.
> >
> > On 28 November 2012 20:03, Johan Hake <email address hidden>
> wrote:
> >> On 11/28/2012 07:15 PM, Martin Sandve Alnæs wrote:
> >>> I fixed this permanently by constructing both test and trial function
> >>> simultaneously on demand using Argument(V) and storing them to
> >>> V._argument_functions. Will the circular references "functionspace <->
> >>> testfunction" be a problem for garbage collection?
> >>
> >> Yes.
> >>
> >> I wonder how this can be implemented without some error prone
> >> heuristics. A robust, but quite intrusive way, would be to always
> >> instantiate a TestFunction together with a TrialFunction whenever one
> >> need the latter.
> >>
> >> Or one could introduce a trial and test space specific counter.
> >> Something like:
> >>
> >> class Argument(.):
> >> _test_and_trial_counters = [dict(test=False, trial=False)]
> >> ...
> >>
> >> class TestFunction(.):
> >> def __init__(.):
> >> .
> >> counters = Argument._test_and_trial_counters
> >> if counters[-1]["test"]:
> >> counters.append(dict(test=False, trial=False))
> >> counters[-1]["test"] = True
> >> Argument(self, ., count=len(counters)*2)
> >>
> >> class TrialFunction(.):
> >> def __init__(.):
> >> .
> >> counters = Argument._test_and_trial_counters
> >> if counters[-1]["trial"]:
> >> counters.append(dict(test=False, trial=False))
> >> counters[-1]["trial"] = True
> >> Argument(self, ., count=len(counters)*2-1)
> >>
> >> Johan
> >>
> >> --
> >> You received this bug notification because you are a member of DOLFIN
> >> Team, which is subscribed to DOLFIN.
> >> https://bugs.launchpad.net/bugs/1083720
> >>
> >> Title:
> >> replace() fails if the new function spaces have a different mesh
> >>
> >> Status in DOLFIN:
> >> Fix Committed
> >>
> >> Bug description:
> >> I submit this bug report following Marie's suggestions on the related
> >> DOLFIN question
> >> (https://answers.launchpad.net/dolfin/+question/215120)
> >>
> >> DOLFIN crashes in the solve() routine after using replace() to replace
> >> the function spaces of a form.
> >>
> >> While the solve succeeds if replaced function spaces have:
> >> - a different polynomial degree or
> >> - a different polynomial degree and a different mesh,
> >> it does not work if the new function spaces is based on a new mesh
> only.
> >>
> >> This is the error message I get:
> >> ***
> -------------------------------------------------------------------------
> >> *** Error: Unable to define linear variational problem a(u, v) = L(v)
> for all v.
> >> *** Reason: Expecting the solution variable u to be a member of the
> trial space.
> >> *** Where: This error was encountered inside
> LinearVariationalProblem.cpp.
> >> ***
> ------------------------------------------------------------------------
> >>
> >> The attached file demonstrates the problem.
> >>
> >> To manage notifications about this bug go to:
> >> https://bugs.launchpad.net/dolfin/+bug/1083720/+subscriptions
> >
>
> --
> You received this bug notification because you are a member of DOLFIN
> Core Team, which is subscribed to DOLFIN.
> https://bugs.launchpad.net/bugs/1083720
>
> Title:
> replace() fails if the new function spaces have a different mesh
>
> Status in DOLFIN:
> Fix Committed
>
> Bug description:
> I submit this bug report following Marie's suggestions on the related
> DOLFIN question
> (https://answers.launchpad.net/dolfin/+question/215120)
>
> DOLFIN crashes in the solve() routine after using replace() to replace
> the function spaces of a form.
>
> While the solve succeeds if replaced function spaces have:
> - a different polynomial degree or
> - a different polynomial degree and a different mesh,
> it does not work if the new function spaces is based on a new mesh only.
>
> This is the error message I get:
> ***
> -------------------------------------------------------------------------
> *** Error: Unable to define linear variational problem a(u, v) = L(v)
> for all v.
> *** Reason: Expecting the solution variable u to be a member of the
> trial space.
> *** Where: This error was encountered inside
> LinearVariationalProblem.cpp.
> ***
> ------------------------------------------------------------------------
>
> The attached file demonstrates the problem.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/dolfin/+bug/1083720/+subscriptions
>