On Fri, Aug 31, 2012 at 1:04 PM, Chris Eldred <[email protected]>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 [email protected]

-- 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