dolfin team mailing list archive

[Shawn Walker <walker@xxxxxxxxxxxxxxx>]

Actually, I have a question about this.  I may have asked this before, so 
forgive me if I repeat.

Suppose my exact solution is sin(2*pi*x).  I would like to compute the 
exact error against this function.  Is this doable?  I know you can 
resample it with a higher order function, but that is lame!  Can't FFC 
treat it like a linear form and use quadrature to evaluate it?  I know it 
isn't really a linear form, but FFC wouldn't know the difference!  :) 
Maybe I am missing something...

- Shawn

On Wed, 10 Jun 2009, Martin Sandve Alnæs wrote:

> The norm definitions should use "inner" instead of "dot" to handle
> tensor fields as well.
>
> Martin
>
>
>
> On Wed, Jun 10, 2009 at 6:14 PM, 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
> > > >
> > > >
> > > > -----BEGIN PGP SIGNATURE-----
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> > > >
> > > > iEYEARECAAYFAkovWqUACgkQTuwUCDsYZdGb3gCfa2gWnzealWzkjPoRj8hf3cr/
> > > > 0EUAoJh4mpaIzRU9eCnnC+XWlupu6SV0
> > > > =so4c
> > > > -----END PGP SIGNATURE-----
> > > >
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> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v1.4.9 (GNU/Linux)
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> > =a7iu
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> >
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