dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

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.

-- 
Anders

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