[Gmsh] Problem with 2D meshes

Min Yan miya at kth.se
Mon Feb 12 23:27:24 CET 2007

Hi Christophe,

I used only second-order *line* and *triangle* elements in a 2D mesh. And I
have turned the "incomplete" option off, but that didn't help.

Now after reading the "Useless nodes" thread, I'm somehow convinced the
problem is caused by these extra nodes. My program pre-sets the global
sparse matrix dimensions according to the number of nodes. The filling of
the global matrices are done by examining each triangles. Now, the existence
of some extra nodes will leave the global matrix with zero-valued diagonal
elements! And that leads to NaN solutions. I wonder if there is any way to
discard, or to identify these extra nodes?

BTW, please also confirm in v2.0 if the nodes are re-ordered by default.

Thanks for the nice package.

Min Yan

On 2/12/07, Christophe Geuzaine <cgeuzaine at ulg.ac.be> wrote:
> The default behavior in Gmsh 2.0 is to use "incomplete" second order
> elements (8-node quads, 20-node hexas, etc.). Maybe that's causing some
> trouble in your code?
> You can revert to using "complete" second order elements by unselecting
> "Use imcomplete second order elements" in Options->Mesh->General.

> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine<http://www.montefiore.ulg.ac.be/%7Egeuzaine>
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