[Gmsh] too slow coherence function

andrew armitatz at gmail.com
Sun Aug 21 17:33:59 CEST 2016


Thank you for the response. The file I submitted was a small one and the
problem was not so obvious. I am attaching a 'real' file​ that I use on my
simulations. It has 3000 cuts in it. This takes 2 hours on a quad core and
1+ hour on a i7 @4ghz. I am using the version 2.13.1.

Kind regards

Andrew Tsiantis

2016-08-21 17:50 GMT+03:00 Christophe Geuzaine <cgeuzaine at ulg.ac.be>:

> > On 19 Aug 2016, at 21:34, andrew <armitatz at gmail.com> wrote:
> >
> > ​Hi,
> >
> > I try to create a 3d mesh from an extruded 2d mesh. The mesh is a simple
> box but with cuts in it of zero width. The geometry is created ok and the
> meshing even when I have 2000-3000 cuts is done in less than a few minutes.
> However when I convert the mesh for use with openfoam I was getting errors.
> By adding the command 'Coherence mesh;' after the creation of the mesh, the
> mesh is converted correctly for use with openfoam by using the ultility
> 'gmshToFoam'.
> Indeed, it's a limitation of our extrusion algorithm with embedded curves
> ("Line In Surface"): it currently creates duplicate vertices. The real fix
> is thus for us to enhance extrusion of embedded curves, but it's not
> trivial due to the way extruded meshes are generated.
> > The problem is in the use of the 'Coherence Mesh'. It takes almost two
> hours to execute while the meshing takes a few minutes. Is there a way to
> improve the Coherence command or to make the same geometry without the
> duplicate nodes that need so much time to be removed?
> >
> > I attached a file that needs 2.5 minutes on a quad core for meshing and
> more than ten minutes to remove 1600 duplicates.
> > I have to create thousands of these meshes so a speedup would be
> welcomed.
> >
> That seems a bit slow: on my laptop meshing and duplicate removal take
> about the same time (2 minutes each). Which version of Gmsh do you use?
> > kind regards
> >
> > Andrew tsiantis
> >
> > <se.geo>_______________________________________________
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> --
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine
> Tetrahedron V, July 4-5 2016: http://tetrahedron.montefiore.ulg.ac.be
> Free software: http://gmsh.info | http://getdp.info | http://onelab.info
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