dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Jun 15, 2009 at 01:09:43PM -0500, Jehanzeb Hameed wrote:
> Thanks. That works. I have a related question about forms.  Can the
> form be defined in python, and then compiled via ffc? For example, I
> did,
> 
> from dolfin import *
> mesh = Mesh("./mesh_2d.xml")
> V = VectorFunctionSpace(mesh, "Lagrange", 1,3)
> u = Function(V)
> M = dot(u,u)*dx
> 
> 
> and then called ffc on this form. This generated a header file. Are
> there any caveats here that I should be careful about?
> 
> -Jehanzeb

It's plain luck this works at all and the mesh will be completely
ignored so do I suggest you just write

  element = VectorElement("Lagrange", tetrahedron, 3)
  u = Function(element)
  M = dot(u, u)*dx

-- 
Anders


> > On Mon, Jun 15, 2009 at 10:09:11AM +0200, Patrick Riesen wrote:
> >> Hi,
> >>
> >> ffc looks for the variables a, L or M to generate a form, so you should
> >> use L  instead of L2, so that ffc notices it.
> >
> > Should be M unless you want to assemble a vector.
> >
> >
> >
> >> regards,
> >> patrick
> >>
> >> Jehanzeb Hameed wrote:
> >> > 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.
> >> >>
> >> >>
> >> >>
> >> >>> 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
> >> >>>>
> >> >>>>
> >> >>>> -----BEGIN PGP SIGNATURE-----
> >> >>>> Version: GnuPG v1.4.9 (GNU/Linux)
> >> >>>>
> >> >>>> iEYEARECAAYFAkovWqUACgkQTuwUCDsYZdGb3gCfa2gWnzealWzkjPoRj8hf3cr/
> >> >>>> 0EUAoJh4mpaIzRU9eCnnC+XWlupu6SV0
> >> >>>> =so4c
> >> >>>> -----END PGP SIGNATURE-----
> >> >>>>
> >> >>>> _______________________________________________
> >> >>>> DOLFIN-dev mailing list
> >> >>>> DOLFIN-dev@xxxxxxxxxx
> >> >>>> http://www.fenics.org/mailman/listinfo/dolfin-dev
> >> >>>>
> >> >>>>
> >> >>> _______________________________________________
> >> >>> DOLFIN-dev mailing list
> >> >>> DOLFIN-dev@xxxxxxxxxx
> >> >>> http://www.fenics.org/mailman/listinfo/dolfin-dev
> >> >> -----BEGIN PGP SIGNATURE-----
> >> >> Version: GnuPG v1.4.9 (GNU/Linux)
> >> >>
> >> >> iEYEARECAAYFAkov28sACgkQTuwUCDsYZdE8KQCdEI7wS27QaNw9knI2U9L+RVST
> >> >> xeUAnRdLrrhAVzsBn6nO1b6CLEpF64ey
> >> >> =a7iu
> >> >> -----END PGP SIGNATURE-----
> >> >>
> >> >> _______________________________________________
> >> >> DOLFIN-dev mailing list
> >> >> DOLFIN-dev@xxxxxxxxxx
> >> >> http://www.fenics.org/mailman/listinfo/dolfin-dev
> >> >>
> >> >>
> >> > _______________________________________________
> >> > DOLFIN-dev mailing list
> >> > DOLFIN-dev@xxxxxxxxxx
> >> > http://www.fenics.org/mailman/listinfo/dolfin-dev
> >>
> >> _______________________________________________
> >> DOLFIN-dev mailing list
> >> DOLFIN-dev@xxxxxxxxxx
> >> http://www.fenics.org/mailman/listinfo/dolfin-dev
> >
> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v1.4.9 (GNU/Linux)
> >
> > iEYEARECAAYFAko2BFQACgkQTuwUCDsYZdF7qACeJkPnmaCDwkc1ffLUsGyyEOtY
> > /kAAnidGRwRLBL7jksqEnf0KsUw4D7hb
> > =k8B2
> > -----END PGP SIGNATURE-----
> >
> > _______________________________________________
> > DOLFIN-dev mailing list
> > DOLFIN-dev@xxxxxxxxxx
> > http://www.fenics.org/mailman/listinfo/dolfin-dev
> >
> >
> _______________________________________________
> DOLFIN-dev mailing list
> DOLFIN-dev@xxxxxxxxxx
> http://www.fenics.org/mailman/listinfo/dolfin-dev

Attachment: signature.asc
Description: Digital signature