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[Anders Logg <logg@xxxxxxxxx>]

Dirichlet BC would need to be added in/after each multiplication and
it should be possible to build it into the mult() operator and make it
efficient.

We can add a class to handle this after the release. Any suggestions
for a good name? ActionMatrix? Action? ActionKrylovMatrix?

-- 
Anders


On Sun, Apr 05, 2009 at 08:31:58AM -0500, Robert Kirby wrote:
> Anders, Martin:
> Dirichlet Boundary conditions?
> 
> 
> On Sun, Apr 5, 2009 at 5:58 AM, Martin Sandve Aln s <martinal@xxxxxxxxx> wrote:
> 
>     UFL defines action so you don't have to rewrite/duplicate your form:
> 
>     a = u*v*dx
>     b = action(a, f) # == f*v*dx
> 
>     Martin
> 
> 
> 
>     On Sun, Apr 5, 2009 at 10:34 AM, Anders Logg <logg@xxxxxxxxx> wrote:
>     > On Sat, Apr 04, 2009 at 08:30:39PM -0500, Robert Kirby wrote:
>     >> Thanks, I'll take a look next week.
>     >>
>     >> One thought that would take a little work but might be worth exploring
>     from the
>     >> ffc end would be
>     >> to define matrix actions in the form compiler that map to KrylovMatrix
>     rather
>     >> than Matrix.
>     >> For example, one can take the Poisson code, replacing the TrialFunction
>     with
>     >> Function, so that
>     >>
>     >> v = TestFunction(V)
>     >> u = Function(V)
>     >> a = dot(grad(v), grad(u))*dx
>     >>
>     >> and then generate code for a KrylovMatrix subclass.  Anders and I
>     experimented
>     >> with the effects of ferari-optimization and found that they were most
>     profound
>     >> in this context.  It also removes the assembly bottleneck since you
>     don't have
>     >> to beat on a sparse matrix.  On the other hand, you don't have the
>     matrix to
>     >> feed to algebraic preconditioners.  No free lunch.
>     >>
>     >> Rob
>     >
>     > This wouldn't require anything on the FFC end. It would just require a
>     > new C++ class which subclasses either of the Krylov matrices (or maybe
>     > a new GenericKrylovMatrix) that takes a linear form (like your 'a'
>     > above) to the constructor and calls assemble() in the overloaded mult().
>     >
>     > This should be easy to add.
>     >
>     >
>     >
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