dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Thu, Dec 04, 2008 at 10:44:27AM +0100, Martin Sandve Alnæs wrote:
> 2008/12/3 Anders Logg <logg@xxxxxxxxx>:
> > On Wed, Dec 03, 2008 at 05:04:37PM +0100, Martin Sandve Alnæs wrote:
> >> 2008/12/3 Garth N. Wells <gnw20@xxxxxxxxx>:
> >> >
> >> >
> >> > Martin Sandve Alnæs wrote:
> >> >>
> >> >> There is a signature:
> >> >>
> >> >>  // Create form on given function space(s) with given coefficient(s)
> >> >> (shared data)
> >> >>  PoissonLinearForm(std::tr1::shared_ptr<const dolfin::FunctionSpace>
> >> >> V0, dolfin::Function& w0) : dolfin::Form(), f(*this)
> >> >>
> >> >> but no signature where both the function spaces and functions are
> >> >> shared pointers. For an application with full use of shared pointers,
> >> >> we need that.
> >> >>
> >> >
> >> > I don't think that it's required. I brought this point up a while ago,
> >> >
> >> >  http://www.fenics.org/pipermail/ffc-dev/2008-November/001923.html
> >>
> >> Quoting this:
> >> """
> >> On Thu, Nov 06, 2008 at 08:14:47PM +0000, Garth N. Wells wrote:
> >> > For the 'shared' versions, shouldn't the coefficients also be shared
> >> > pointers?
> >>
> >> It's not necessary since these arguments will not be stored as
> >> data. They will just be assigned to the coefficients.
> >> """
> >>
> >> That's just plain wrong. Through Coefficient::attach, the Form will
> >> store shared pointers to them with NoDeleters, and these pointers
> >> won't share the reference count of an eventual shared pointer I
> >> have in my application.
> >
> > Yes, that seems to be wrong.
> >
> > Do you need shared_ptr only in the constructors or do you also want
> > shared_ptr for the assignment operator?
> 
> An additional assignment operator would be nice.

ok, just add it (see below).

> > Is it possible to reuse the DOLFIN-wrappers from dolfinformat.py in
> > FFC? It would be practical if we could reuse the same code since it's
> > a bit messy to generate with all the different combinations of
> > constructors with and without shared_ptr etc. It would also increase
> > the chances for generating compatible code.
> 
> > Perhaps it can be placed in UFC, say under src/utils/python/dolfin?
> > It could be a single function that gets the form name(s) as input, the
> > list of coefficient names etc so it would be independent of the
> > form-compiler.
> 
> I'm not reusing that code because it uses some ffc specific
> assumptions and there are things I don't find flexible enough.
> In particular, I don't want to duplicate element code.
> I'll keep my code with no dependencies, and then we
> can see whether we can agree on how to reuse it.

Sounds good. If you find a good solution, I'll be happy to reuse it
for FFC, including the additional constructors.

-- 
Anders

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