dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sat, Jun 28, 2008 at 08:55:44PM +0200, Johan Hake wrote:
> Hello!
> 
> I tried to compile an advection diffusion form using Streamline Upwind Petrow 
> Galerkin stabilazing method, similar to the one introduced in DOLFIN 0.6.4. 
> Using 3 dimensional and first degree Lagrange elements, FFC/g++ chokes when 
> the produced code is compiling. It wont finish compile... Is this a known 
> problem and a limitation of FFC/g++?

Try compiling with the -r quadrature option. I guess this is not
supported in the JIT compiler yet, but could easily be added. There
should be an option

  dolfin_set("form representation", "quadrature");

in the same way as there is an option "optimize". See if you can
figure it out and send a patch, or else file a bug report.

Options are added in DefaultParameters.h in DOLFIN and the JIT
compiler is in jit.py in FFC.

Possible options for "form representation" are "tensor", "quadrature"
and (unsupported at the moment) "symbolic" (for SyFi).

The quadrature representation generates much less code than the tensor
representation.

> In PyCC I use DOLFIN to assemble the same system matrix, but instead of using 
> one form for the whole system I split the form into at least 4 different 
> forms. These compiles smoothly and after I have assembled the matrices I just 
> add them together. 
> 
> This approach is not possible using the present DOLFIN linear algebra 
> interface, as sum of matrices is not supported. Is this something we want for 
> the future? 

I think so.

-- 
Anders

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