[Gmsh] [FORGED] Re: Windows, Ubuntu give different meshes

[Gib Bogle]

I'm interested in knowing how the differences arise.  I can understand how different machines, compilers can give numerical results that differ at the limits of the selected precision, but it's not obvious how this leads to the generation of different meshes.


Gib

________________________________
From: gmsh <gmsh-bounces at ace20.montefiore.ulg.ac.be> on behalf of moritz braun <moritz.braun at gmail.com>
Sent: Monday, 1 July 2019 10:28 p.m.
To: Christophe Geuzaine
Cc: gmsh at onelab.info; gmsh at geuz.org
Subject: [FORGED] Re: [Gmsh] Windows, Ubuntu give different meshes

Dear Christophe

I assume  identical  geometries leading to different meshes
between different versions of  redhat 7.4 to 7.6
can be expected.
I was quite surprised because my self consitent code behaved differently depending
on the redhat version and now I understand!

Regards

Moritz


On Fri, Jun 28, 2019 at 8:04 AM Christophe Geuzaine <cgeuzaine at uliege.be<mailto:cgeuzaine at uliege.be>> wrote:


> On 27 Jun 2019, at 03:33, Gib Bogle <g.bogle at auckland.ac.nz<mailto:g.bogle at auckland.ac.nz>> wrote:
>
> I have been testing with the demo file cube.geo:
>
> lc = 0.3;
> Point(1) = {0.0,0.0,0.0,lc};
> Point(2) = {1,0.0,0.0,lc};
> Point(3) = {1,1,0.0,lc};
> Point(4) = {0,1,0.0,lc};
> Line(1) = {4,3};
> Line(2) = {3,2};
> Line(3) = {2,1};
> Line(4) = {1,4};
> Line Loop(5) = {2,3,4,1};
> Plane Surface(6) = {5};
> tmp[] = Extrude {0,0.0,1} {
>   Surface{6};
> };
> Physical Volume(1) = tmp[1];
>
> I generate the mesh file at the command line like this:
>
> gmsh -3 cube.geo
>
> on a Windows 7 machine and on Ubuntu 16.04.  The gmsh version is 4.3.0.
>
> I find that the meshes created on the two systems are a bit different.  On Windows the mesh has 137 nodes and 372 elements, while on Ubuntu it has 136 nodes and 373 elements.
>
> Should I be concerned about this?

No, on the same machine the meshes should be identical, but across OSes (and different compilers) small variations are normal.

Christophe


>
> Thanks
> Gib
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-
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine




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