On Fri, Aug 31, 2012 at 3:52 PM, Chris Eldred <chris.eldred at gmail.com>wrote:
> Ok- so if I have a multicomponent field, I should define the number of > dofs at a point for that field to be the total number of dofs I want > for that field. Ex a 2 component field with 2 dofs per component > should have 4 dofs defined, not 2. Num components just serves to give > additional info about the field but it is not used in defining or > manipulating the PetscSection. Yes. Matt > On Fri, Aug 31, 2012 at 2:29 PM, Matthew Knepley <knepley at gmail.com> > wrote: > > On Fri, Aug 31, 2012 at 1:04 PM, Chris Eldred <chris.eldred at gmail.com> > > wrote: > >> > >> I was wondering how components were treated in PetscSection- my > >> understanding is that a field with multiple components and multiple > >> dofs would have those dofs duplicated for each component, but that > >> does not appear to be the case. For example, let's say I have a field > >> with 2 components and 2 dofs that covers 10 points. I expected that it > >> would have size 40: 4 dofs per point x 10 points. Instead, it appears > >> to have size 20: 2 dofs x 10 pts. > > > > > > Yep, that is not the case. What if the components are discretized with > > different numbers of dofs on different points? This definitely happens. > > > >> > >> What then are components in PetscSection- is it just a way of telling > >> the code that the dofs associated with a field at a point are really > >> split across multiple components (ie for my example, I should define 4 > >> dofs at each pt instead of 2)? How does that then interact with the > >> re-ordering done in DMComplexVecGetClosure? > > > > > > The idea of components is to give you an idea what kind of field you are > > dealing with. I know I don't go so far as to tell you its a vector, or a > > pseudo-vector, etc. I am not sure where to draw the line yet. Within > > GetClosure(), the dofs for reversed points are separately reversed per > > component. > > > > Matt > > > >> > >> > >> -- > >> Chris Eldred > >> DOE Computational Science Graduate Fellow > >> Graduate Student, Atmospheric Science, Colorado State University > >> B.S. Applied Computational Physics, Carnegie Mellon University, 2009 > >> chris.eldred at gmail.com > > > > > > > > > > -- > > What most experimenters take for granted before they begin their > experiments > > is infinitely more interesting than any results to which their > experiments > > lead. > > -- Norbert Wiener > > > > -- > Chris Eldred > DOE Computational Science Graduate Fellow > Graduate Student, Atmospheric Science, Colorado State University > B.S. Applied Computational Physics, Carnegie Mellon University, 2009 > chris.eldred at gmail.com > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120831/e6d0c74a/attachment.html>
