[dune-pdelab] question about slow routines in pdelab!!!

[Jö Fahlke]

Am Thu, 27. Oct 2011, 16:42:42 +0200 schrieb Nagaiah Chamakuri:
> test has been done using Pk3DLocalFiniteElementMap.
> thank you

> > Am Thu, 27. Oct 2011, 15:03:11 +0200 schrieb Nagaiah Chamakuri:
> > > Last week, I have written in my previous mail(to dune mailing list) that
> > > ALUGRID is slower than UG grid.
> > > http://lists.dune-project.org/pipermail/dune/2011-October/009320.html
> > > To check this, I was doing some simple test using UG and ALU grids. And
> > > realized
> > > found that some FE routines are taking long time for ALUGRId comparing
> > with
> > > UG grid.
> > > Specifically, "*const typename Traits::FiniteElementType &fe =
> > > pfem->find(*it);*"
> > > For me it is hard to understand  that why does "*FE type* (pfem->find)"
> > > takes longer for ALUGRID.
> > > I would expect that UG and ALU should take same (or comparable) time.

Here is the only code in that function that may have a grid-dependent
execution time (from [1]):

  // get the vertex indices
  unsigned int vertexmap[4];
  for (unsigned int i = 0; i < 4; ++i)
      vertexmap[i] = is.subIndex(e,i,3);

It is known that _global_ ID's are slow for ALUGrid[2].  However, in this
instance an IndexSet is used, and as far as I know that should be pretty
quick.  Maybe it is because the index of a subentity of an element is
requested instead of the index of a full entity?

I doubt anyone on the PDELab list can tell you anything definite, so you have
to go back to the Dune list with the information you collected.

Bye,
Jö.

[1] https://svn.dune-project.org/svn/dune-pdelab/trunk/dune/pdelab/finiteelementmap/pk3dfem.hh

[2] Usually there is a way to avoid using global ID's, so this isn't an issue
    most of the time.
-- 
Jorrit (Jö) Fahlke, Interdisciplinary Center for Scientific Computing,
Heidelberg University, Im Neuenheimer Feld 368, D-69120 Heidelberg
Tel: +49 6221 54 8890 Fax: +49 6221 54 8884

featured product: Debian GNU/Linux - http://www.debian.org
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 828 bytes
Desc: Digital signature
URL: <https://lists.dune-project.org/pipermail/dune-pdelab/attachments/20111027/78b1d845/attachment.sig>