dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

kent-and@xxxxxxxxx wrote:
> > Anders Logg wrote:
> > > On Wed, Aug 20, 2008 at 04:17:11PM +0200, kent-and@xxxxxxxxx wrote:
> > > > > kent-and@xxxxxxxxx wrote:
> > > > > > > Can Assembler::assemble_system be easily generalised to an Array of
> > > > > > > DirichletBC,
> > > > > > >
> > > > > > >    Array<DirichletBC*> bcs
> > > > > > >
> > > > > > > so that vector equations can be handled?
> > > > > > >
> > > > > > > Garth
> > > > > > Good point, I'll have a look.
> > > > > OK, I'm taking a look at the moment with a view to generalising
> > > > > Assembler::assemble_system for nonlinear problems (Newton solve).
> > > > >
> > > > > Garth
> > > > OK, in the present implementation, the matrix does not have 1 on the
> > > > diagonal
> > > > associated with bcs. It will be 1 times the number of elements (or
> > > > faces)
> > > > associated
> > > > with it.
> > > >
> > > > This weighting can be stored but it is not presently done.
> > > >
> > > > Kent
> > > I amazed you even managed to implement that code. It's huge. We should
> > > try to break it up so we can reuse as much as possible between that
> > > and the standard assemble() function.
> > I was impressed :).
> >
> > Now that what's needed is clear, it can be broken up. It looks to me
> > like a number of the existing functions can be extended slightly and
> > then re-used. The actual code for applying the bcs is not very long.
> >
> > Garth
>
> It is a mess,  way to large and should be broken up.
> It is also a bit "difficult" to break up. For instance, the
> coefficents may or may not need to be computed depending
> on whether it has been computed earlier ie. after computing coefficients
> for a macro element it should not be needed when computing the cell integral.
> The same applies to dof_maps. 

Is there so much overhead involved in this? We're probably recomputing 
these things in the other assembly functions. Perhaps there is 
noticeable overhead, and that's why assemble_system is faster?

Hence it is hard to group everything associated
> with eg a cell integral together in a function. Or maybe it can be done
> with a set
> of bools that contains the state of the various structures.

I'm testing now whether an Array of boundary condition can be applied as 
simply as I think. If that works, assemble_system should be fully 
functional and we can try breaking it up.

Garth


> Kent