ffc team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

On 04/09/10 17:20, Johan Hake wrote:
> On Saturday September 4 2010 08:55:42 Anders Logg wrote:
> > On Sat, Sep 04, 2010 at 08:49:43AM -0700, Johan Hake wrote:
> > > On Saturday September 4 2010 05:03:04 Anders Logg wrote:
> > > > All of the problems seem to come from the Python tests and demos with
> > > > std::bad_cast. Perhaps something with the SWIG layer?
> > >
> > > Yes I have noitced this before. Not sure why but I have not been able to
> > > compile the wrapper code with -O3
> >
> > Isn't it just that the wrapper code (like the form files) can be very
> > large (very many lines of code in a single function or file) so the
> > compiler runs out of memory or takes a very long time to compute the
> > optimizations?
>
> It might be that the dolfin wrapper file it too large. But I have tried
> compiling the a much smaller wrapper code and it also bailed out for -O3.

I've never had a problem with -O3 when using the quadrature 
representation. It can be a problem for the tensor contraction, but by 
the time you run into this limitation the quadrature code is much faster 
anyway. Why I am seeing now for a particular problem is that Kristian's 
FFC optimisations so good that -O3 and -O0 make no difference because 
insertion is dominating.

The tensor contraction would be more compiler friendly (and most likely 
efficient) if it didn't unroll loops, but used fixed size loops and let 
the compiler do tricks on those.

Garth

> Johan
>
> > I changed to -O2 for the same reason in the Dorsal PETSc package
> > file. I think -O3 is ok for PETSc but I think of -O2 as optimize and
> > -O3 as try even harder.
> >
> > --
> > Anders