[petsc-dev] components in PetscSection

[Chris Eldred]

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.

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?

-- 
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