[Gmsh] meshing partitions

[Christophe Geuzaine]

> On 9 May 2020, at 18:09, Hansjoerg Seybold <hansjoerg at fisica.ufc.br> wrote:
> 
> Hello,
> I am trying to mesh a model consisting of several physical groups each
> group at a time and then merge the meshes for the different physical
> groups afterwards. The reason why I am trying to perform this "domain
> decomposition" is that the meshing of the full model takes over 5 days
> and exceeds the runtime limit of the queuing system.
> 
> However I could not find a simple way to apply the  "Mesh 2" to a
> specific physical group. Gmsh always tries to mesh the whole model.
> 

You could either delete the parts you don't want to mesh; or hide the parts you don't want to mesh (cf. the `Show` and `Hide` commands in .geo script, or `setVisibility()` in the api) and use the `Mesh.MeshOnlyVisible` option.

> My question would be if anybody has a hint how to perform this meshing
> in parts and how to combine the resulting meshes into a single final
> model.
> 

That's trickier as each mesh will be independent. The development snapshot allows you to set the starting node/element tag (Mesh.FirstNodeTag, Mesh.FirstElementTag), which will help. Removing duplicate nodes when you merge things together can be done with Coherence Mesh (in .geo files) or removeDuplicateNodes() in the api.

PS: 5 days to perform a 2D mesh ? Anything special in the geometry/size field? If you don't do this already at least recompile Gmsh with OpenMP enabled, and mesh in parallel?

Christophe

> Thank you very much.
> 
> Best,
> hansjoerg
> 
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine