[Gmsh] mesh element sizes

[Peter Metaxas]

Hi.

Troubled by some results on a more complex geo file (I noticed that using mesh element sizes of 2.5 and 3 generated identically sized .msh files) I did a test of meshing on a single line with a length of 10 (ie. 1D meshing only). In both cases (actual and test cases), I specify "desired mesh element sizes at the geometrical points of the model" using the point command.

Here's my test geo file:

length=10.0;
disc=1.0;

Point(1)={length/2.0,0.0,0.0,disc};
Point(2)={-length/2.0,0.0,0.0,disc};
Line(1)={1,2};

I expected that using a mesh element size of 1 (specified using "disc") would give me 10 elements along my line. It however only gives me 9 (8 nodes along the line). The results are shown below:

disc=1                   9 elements
disc=0.9                11 elements
disc=0.9999         10 elements

The same general type of effect seems to hold for other desired element sizes: disc=2.5 yields 3 elements (rather than the expected 4 elements which can be obtained using disc=2.4).

I couldn't find information on such effects - apologies if it has been discussed previously though. Is this maybe a known effect of rounding, precision or the meshing algorithm itself?

Thanks in advance.

Best regards, Peter.
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