On Tue, Apr 22, 2008 at 09:21:48PM +0200, Dag Lindbo wrote: > Anders Logg wrote: > > On Mon, Apr 21, 2008 at 09:35:30PM +0200, Dag Lindbo wrote: > >>>> Why do I care? I'm looking at the current state of the LinearPDE class. > >>>> Here, the solution vector is a member function, and the solution > >>>> Function is initialized with a reference to this vector. I.e. the > >>>> LinearPDE (not the DiscreteFunction) owns the solution vector. This is > >>>> of course a problem if the LinearPDE goes out of scope before the > >>>> solution function (bug 24). It is also a bit counter-intuitive. > >>>> > >>>> If it was possible to do an initialization like above, then the solve() > >>>> method would simply do > >>>> u.init(mesh, form, 1); > >>>> GenericVector& x = u.vector(); > >>>> <solve> > >>> There is a member local_vector in DiscreteFunction that could be used > >>> for this. If this is nonzero, then the DiscreteFunction owns its data. > >>> > >>> See if you can figure out a good way for the DiscreteFunction to know > >>> that it should take responsibility for the vector here. > >>> > >> Right... I don't see how to do this without breaking the encapsulation of > >> both Function and DiscreteFunction (making LinearPDE friend in both). > >> Bundle attached. > >> > >> Garth, does this look OK? > >> > >> In essence, the member x is removed from the LinearPDE class. in > >> LinearPDE::solve I do > >> > >> (...) > >> Vector b; > >> Vector* x = new Vector(); > >> (... call solver etc) > >> > >> u.init(mesh, *x, a, 1); > >> DiscreteFunction& uu = dynamic_cast<DiscreteFunction&>(*u.f); > >> uu.local_vector = x; > >> > >> /Dag > > > > Looks like a good temporary solution to me. > > > > I expect when we're done and happy with the linear algebra classes > > (which should be soon), we will have a similar party with the function > > classes... :-) > > > > The fact that the pointer to x goes out of scope and trusts the > DiscreteFunction to clean up the vector makes me a bit queasy (this can > probably break in the future, causing a big leak). You should probably > verify independently that nothing broke because of this revised > LinearPDE (but for me it has been working nicely today). > > On a more general note, I'm pretty happy with the state of the LA now > that op[] is back and the down_cast<Foo> mechanism has been explained. > > As a benchmark I ran a Inc. Navier-Stokes solver (based on the old > module, which uses a lot of 'manual' LA) and got a modest slowdown: > (tip yesterday) 53.071u 6.708s > (0.7.2) 50.803u 1.700s > It may also be worth mentioning that I got the same numerical values > (for some residual norm) even after hundreds of time steps. > > /Dag
ok. It might be possible to find some optimizations when things have stabilized. -- Anders _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
