dolfin team mailing list archive

[Jehanzeb Hameed <jhameed2@xxxxxxxxxxxx>]

I cant figure out how to generate a form file for norm, in C++. The
problem is that the form is quadratic in its arguments, and so isn't a
valid form according to ffc user manual. I tried it anyway, making a
file like this (just for testing):.

vecElement = VectorElement("Lagrange", "triangle", 1,3)
u = Function(vecElement)
L2 = dot(u,u)*dx

ffc doesnt make .h file, and exits with the following message:

"No forms or elements specified, nothing to do."

I tried compiling by "ffc -r quadrature l2norm.form", and again got
the same message.

Can someome please help amd point out what I can do?

Thanks,
-Jehanzeb

On Wed, Jun 10, 2009 at 11:14 AM, Anders Logg<logg@xxxxxxxxx> wrote:
> On Wed, Jun 10, 2009 at 09:58:20AM -0500, Jehanzeb Hameed wrote:
>> Thanks. So I guess that means no such facility is available in C/C++ ?
>
> No, since the computation depends on the space the functions are in
> and so the code needs to be generated. In C++, you need to define a
> form file for the norm. Look at
>
>  site-packages/dolfin/norm.py
>
> for how to define the norms.
>
> --
> Anders
>
>
>> On Wed, Jun 10, 2009 at 2:03 AM, Anders Logg<logg@xxxxxxxxx> wrote:
>> > On Tue, Jun 09, 2009 at 05:11:48PM -0500, Jehanzeb Hameed wrote:
>> >> Hello,
>> >>
>> >> Is there a builtin function in dolfin to compute L^2 or H_1 norms? If
>> >> so, can you please point it out. If not, are there support functions
>> >> (e.g. a Gauss Quadrature table, computation of Jacobians, etc) which
>> >> can help in this?
>> >
>> > Yes, this is available in the DOLFIN Python interface:
>> >
>> >  norm(v)
>> >
>> > The default computes the L^2 norm. Several options are available:
>> >
>> >  L^2:     norm(v, 'L2')
>> >  H^1:     norm(v, 'H1')      includes L^2 term
>> >  H^1_0:   norm(v, 'H10')     does not include L^2 term
>> >  H(div):  norm(v, 'Hdiv')    includes L^2 term
>> >  H(div):  norm(v, 'Hdiv0')   does not include L^2 term
>> >  H(curl): norm(v, 'Hcurl')   includes L^2 term
>> >  H(curl): norm(v, 'Hcurl0')  does not include L^2 term
>> >
>> >
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>> > =so4c
>> > -----END PGP SIGNATURE-----
>> >
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