dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sun, Jun 29, 2008 at 09:03:07PM +0200, Dag Lindbo 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++?
> 
> I worked a bit with this kind of form and also had impossibly long
> compilation times (back in the 0.6.4 day). The solution then was to
> compile the implementation of the form into a separate object. In order to
> do this I made a patch for FFC so that it emit the implementation in a
> separate file from the declarations. Then the form could be compiled once
> (often over lunch) instead of each time I tweaked the solver code. Also, I
> had then the option to build the form implementation with less
> optimization (which made a huge difference). However, my patch for FFC was
> never taken in. No hard feelings over this, but I still think it is a
> worthwhile option.

I don't remember this. I must have just forgotten about the
patch. Send it again.

There is support in UFC (utils) for generating separate .cpp and
header files.

-- 
Anders


> Another C++ approach to this compile-form-once problem is to wrap it in a
> "factory" class and build that one with less optimization. Form
> compilation times have improved though :)
> 
> /Dag
> 
> >
> > 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?
> >
> > Johan
> > _______________________________________________
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> >
> 
> 
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