dolfin team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

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.
>
> --
> Anders
>
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.9 (GNU/Linux)
>
> iEYEARECAAYFAknYbQkACgkQTuwUCDsYZdHiCgCeOk8lUh47at3BIt9E7/Xkinw1
> 3KEAniQRFbDbirrEOgNznCFdPaLfKD9E
> =YC3r
> -----END PGP SIGNATURE-----
>
> _______________________________________________
> DOLFIN-dev mailing list
> DOLFIN-dev@xxxxxxxxxx
> http://www.fenics.org/mailman/listinfo/dolfin-dev
>
>