On Tue, 30 Mar 2010, Derek Gaston wrote:
On Mar 30, 2010, at 12:09 PM, Roy Stogner wrote:
Yeah, and I'm starting to wonder if I did it right. While I was
preparing this patch I think I noticed a bug that would kill the
convergence rates for hp refinement on C0 elements in 2D/3D - a
situation in which I never did get exponential convergence.
No point in attempting a fix now, though, since I won't have time to
test it. The app code I'm working on now is LAGRANGE-only and so for
us is p-refinement-incompatible; and without that I've got no excuse
to spend as much time as it would take to get hp working well by
myself. I'd try and conscript Vikram, but he's got a tough enough
problem with h refinement alone on some of these non-conforming QoIs.
I don't even know if Taylor-Hood elements are LBB-stable under
adaptive hp refinement.
Just for catloguing the problem... can you give a small description? Maybe
someone else can fix it...
To handle p-refinement, in that snippet of system_projection.C that
Lorenzo and I just fixed, we assume that the basis is p-hierarchic,
which assumptions allows us to either ignore the highest indexed DoF
(when lowering p) or set it equal to 0 (when raising p).
But to handle h-refinement on arbitrary elements, we have a more
complicated system on hanging nodes: vertex DoFs are indexed in
ascending order from 0 up, but edge/face DoFs on hanging nodes are
indexed in descending order from n_dofs_at_node-1 down.
This means that the current project_vector() code is definitely buggy
for the hp case, and it's possible that the constraint generation code
(which uses the same p-hierarchic assumption) has the same problem.
---
Roy
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