Anders Logg wrote: > 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. >
Try accessing the underlying data type directly and operate on it. It will avoid the overhead of virtual function call and more inlining is possible. Garth _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
