ffc team mailing list archive

[Jed Brown <fenics@xxxxxxxx>]

On 20 Sep 2007, k.b.oelgaard@xxxxxxxxxx wrote:

> Quoting Jed Brown <fenics@xxxxxxxx>:
>
>> The issue with general powers ought to be pretty easy to rectify.  The
>> inability to take roots or inverses of a sum might be deeper, but it is
>> essential for me to use FFC.  Any tips about how to go about this?
> 
> Just substitute your sum with one function, and compute the sum elsewhere.

Can I do it within this form?  I can't take derivatives from within
Dolfin, but I guess I could outsource that job to another form?  Clumsy
but workable.

>> To avoid the massive hit for computation, I should be able to use
>> quadrature.  Presumably the tensor-based code is more efficient, I
>> could use quadrature for development and only generate the tensor
>> code for production.  Alternatively, I should be able to compile the
>> form into its own object file and then just link to it.  This doesn't
>> help for when I edit the form, but that shouldn't happen too often.
>
> This should be fixed now.

Quadrature works now (FFC still takes a few minutes) and generates code
that is less than 1 MiB (instead of 16 MiB) for the Newton case.  The
Newton case without quadrature generates 16 MiB of code and I killed the
build job after 5 hours with my CPU pegged and 600 MiB memory usage.
The code explosion is confusing to me because there is basically nothing
to do.  There are no test/trial functions involved in defining D2 (or
eta).

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