[Gmsh] Point xxxx is identical with point yyyy. -- what does this mean?

Steve Talent talent at analograils.com
Sat Jun 5 03:10:43 CEST 2010

I'm running a series electrostatics solutions on different
configurations of an integrated circuit device called a "fringe
capacitor". I'm using several different tools to go from the IC layout
software to a PDE solver (Elmer).

I'm using Gmsh for 3D meshing because it's easy to create a volume
surrounding the capacitor "plates". Each plate looks like a comb with
very long teeth and the teeth of those plates are interdigitated.

I'm using netgen to mesh the surfaces and export ".stl" for input into
Gmsh. Initially, all dimension are integer valued and represent
nanometers. The smallest dimension is ~200 nm and the largest is ~60000
nm. When the larger dimension is less than about ~60000, I have no
problems. Above that, I start seeing messages like...

"Warning:  Point 6527 is identical with point 6373."

... and gmsh never completes.

Does "identical" mean exactly identical, or just very close?

Are there any run-time parameters I can set to resolve this problem?

> cat gmsh.geo
Merge "boxng.stl";
Merge "x0ng.stl";
Merge "x1ng.stl";
Surface Loop (3) = { 1 };
Surface Loop (4) = { 2 };
Surface Loop (5) = { 3 };
Volume (6) = { 3, 4, 5 };
Physical Surface(1)={1};
Physical Surface(2)={2};
Physical Surface(3)={3};
Physical Volume(1)={6};

> gmsh gmsh.geo 
Constructing Delaunay tetrahedralization.
Warning:  Point 6527 is identical with point 6373.
Warning:  Point 2771 is identical with point 5682.
Warning:  Point 8527 is identical with point 8337.
Warning:  Point 2780 is identical with point 5692.
Warning:  Point 6528 is identical with point 6678.
Warning:  Point 4564 is identical with point 4566.
Warning:  Point 8895 is identical with point 9063.
Warning:  Point 6211 is identical with point 6043.
Warning:  Point 6215 is identical with point 6375.
Warning:  Point 9065 is identical with point 8896.
Delaunay seconds:  1.75
Creating surface mesh.
Perturbing vertices.
Delaunizing segments.
Constraining facets.
Segment and facet seconds:  3.27
Removing unwanted tetrahedra.
Hole seconds:  0.04
Repairing mesh.
Repair seconds:  0.07
Jettisoning redundants points.

Writing nodes.
Writing elements.
Writing faces.
Writing edges.

Output seconds:  0.05
Total running seconds:  5.19


  Input points: 27161
  Input facets: 54266
  Input segments: 81399
  Input holes: 0
  Input regions: 0

  Mesh points: 44823
  Mesh tetrahedra: 256688
  Mesh triangles: 523370
  Mesh subfaces: 89610
  Mesh subsegments: 36291