Comment 6 for bug 956979

On 16 March 2012 15:17, Anders Logg <email address hidden> wrote:
> On Fri, Mar 16, 2012 at 03:04:14PM -0000, Martin Sandve Alnæs wrote:
>> On 16 March 2012 15:49, Johan Hake <email address hidden> wrote:
>> > This is really a duplication of bug 897372, which compared FFc and SFC,
>> > as SFC compiles the attached form just fine. The generated code is much
>> > smaller. Talking with Martin, I get the impression that FFC does not use
>> > the information UFL provides about the internal structure of the
>> > different sub expressions. I got the impression that FFC lump the whole
>> > expression into a large string.
>>
>> ... for arguments to MathFunctions that is, according to earlier
>> comments from Kristian.
>>
>> Material models for biological tissue often have rather complex
>> arguments to e.g. exp.
>>

Which explode when linearised.

>> But Johan, did you try _with_ ffc optimization? I believe that may
>> improve the size of the generated code.
>
> I thought the issue was the number of quadrature points used by FFC
> trying to integrate the expression exactly. Does it not help to reduce
> the quadrature order?
>

This doesn't impact on the generation time, just the runtime.

The linearisation of complicated functions (fractions, etc) can really blow up.

Garth

> --
> Anders
>
>
>> Martin
>>
>>
>> > Subdividing this string is probably
>> > suboptimal compared to using the information already stored in UFL.
>> >
>> >
>> > Title:
>> >  FFC generate code which cannot be compiled
>> >
>> > Status in FEniCS Form Compiler:
>> >  New
>> >
>> > Bug description:
>> >  I have a viscoelastic biomechanics form which generate an .h file
>> >  which is 45M large, with a single line length of 44M characters long.
>> >  This wont compile with gcc. No optimization enabled at all.
>> >
>> > To manage notifications about this bug go to:
>> > https://bugs.launchpad.net/ffc/+bug/956979/+subscriptions
>>
>
> --
> You received this bug notification because you are a member of FFC Core
> Team, which is subscribed to FFC.
> https://bugs.launchpad.net/bugs/956979
>
> Title:
>  FFC generate code which cannot be compiled
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ffc/+bug/956979/+subscriptions

--
Garth N. Wells
Department of Engineering, University of Cambridge
http://www.eng.cam.ac.uk/~gnw20