[Gmsh] Scale dependent FATAL error, multiple times in surface mesh

[Anthony Costa]

Hi All,

My geo file is as follows:
lc = 0.000001;

ctm = 0.001;

negx = 0.495*ctm;
negy = 0.48*ctm;
negz = -0.008*ctm;
posx = 0.545*ctm;
posy = 0.496*ctm;
posz = 0.030*ctm;

Point(1) = {negx, negy, negz, lc};
Point(2) = {posx, negy, negz, lc};
Point(3) = {posx, posy, negz, lc};
Point(4) = {negx, posy, negz, lc};
Point(5) = {negx, negy, posz, lc};
Point(6) = {posx, negy, posz, lc};
Point(7) = {posx, posy, posz, lc};
Point(8) = {negx, posy, posz, lc};
Line(1) = {4,3};
Line(2) = {3,7};
Line(3) = {7,8};
Line(4) = {8,4};
Line(5) = {4,1};
Line(6) = {1,5};
Line(7) = {5,8};
Line(8) = {5,6};
Line(9) = {6,2};
Line(10) = {2,1};
Line(11) = {2,3};
Line(12) = {7,6};
Line Loop(13) = {3,4,1,2};
Plane Surface(14) = {13};
Line Loop(15) = {5,6,7,4};
Plane Surface(16) = {15};
Line Loop(17) = {10,6,8,9};
Plane Surface(18) = {17};
Line Loop(19) = {12,9,11,2};
Plane Surface(20) = {19};
Line Loop(21) = {1,-11,10,-5};
Plane Surface(22) = {21};
Line Loop(23) = {8,-12,3,-7};
Plane Surface(24) = {23};
Surface Loop(25) = {24,18,22,14,16,20};
Volume(26) = {25};
Physical Volume(27) = {26};
Physical Surface(28) = {14};
Physical Surface(29) = {22};
Physical Surface(30) = {18};
Physical Surface(31) = {24};
Physical Surface(32) = {16};
Physical Surface(33) = {20};

It's a very small (on the order of microns) box to be meshed in 3D.
Compiling this mesh throws an error:
Fatal   : ERROR: Edge 4 - 9 multiple times in surface mesh
debug!
Aborted (core dumped)

Amazingly, if I scale the the mesh to be on the order of millimetres
and adjust the length characteristic accordingly (by changing the
variables 'lc' to 0.001 and 'ctm' to 1), the mesh compiles just fine.
Further, at very low characteristic length, the mesh compiles fine.
These mesh densities are nowhere near high enough for my problem, so
I'm quite concerned. I feel like running into a computational
precision boundary here is unlikely ... the mesh isn't THAT dense yet!

Thanks much,
Anthony

-- 
Anthony B. Costa
Purdue University
Department of Chemistry
560 Oval Drive, #365
West Lafayette, IN 47907