dolfin team mailing list archive

[Johan Jansson <johanjan@xxxxxxxxxxxxxxxx>]

On Thu, Jul 13, 2006 at 01:02:29PM +0200, Garth N. Wells wrote:

...

> Johan, any news on wrapping the uBlas functions? It would be good to
> sort this out before proceeding too far with the linear algebra clean
> up. We could change uBlasMatrix to look like
> 
>   template<class Mat>
>   class uBlasMatrix : public Variable, public GenericMatrix, 
>                       public uBlasKrylovMatrix
>   {
>     public:
>       .
>       .
> 
>     private:
>       Mat* mat;
>   }
> 
> Would this work with Swig?

This is the same situation as before, i.e. SWIG needs to know about
Mat to be able to instantiate uBlasMatrix.

> If we make this change, we should consider to what extent the
> limitations of Swig should affect the future development of DOLFIN. 
> 
> Another possibility is to consider Boost.python. This came up on the
> DOLFIN mailing list last year when PyDOLFIN started. It seems to offer
> better compatibility with C++. After a quick look on the web, I saw that
> the guys at Simula have experience with both Swig and Boost.python, so
> they could be a very useful resource. There is a oldish presentation
> comparing different tools at
> http://people.web.psi.ch/geus/talks/europython2004_geus.pdf .
> 

It's not that this is impossible to solve with SWIG, it's that it
requires extra code to solve (i.e. it's not fully automatic). And the
more code we have, the harder it is to maintain DOLFIN, so we should
keep the code as small as possible.

But the example you posted with a manual wrapping of uBlas gives me an idea:

http://www2.laas.fr/~tlemaire/viewsvn_jafar/?do=view&project=jafarModules&path=/trunk/jmath/include/jmath/ublasMatrix.i

Perhaps we can redefine the uBlas classes for SWIG in a minimal way,
since we're not interested in exporting the entire uBlas interface at
this point. I'll try that. If it's just a matter of essentially just
defining class names, then that's an ok solution.

I should also take a look at Boost.Python and Pyste (automated
interface generator), I haven't spent any time experimenting with that
yet. It does have advantages.

I don't think the limitations of SWIG (or other automatic interface
generators) should affect the design of the DOLFIN interface. But I
think it's also true that if we design the DOLFIN interface well, then
it won't be hard to wrap it (and the interface should then also be
small).

But I'm not saying the templated uBlasMatrix is a bad design, it uses
templates to minimize code size, which is what we want. Let's try to
make it work.

  Johan