[Gmsh] Trouble with 1D meshing in gmsh-4.0.2

[Pat Prodanovic]

Hello,
 
I am having a bit of trouble with 1D meshing using gmsh-4.0.2. It seems like there is a new 1D meshing algorithm that is much slower than what was available in previous versions. Allow me to illustrate:

Consider a rectangle, 700 m by 1200 m whose edges are resampled to a 10 m spacing. The example also has a line embedded in a surface, with an edge spacing of 25 m. This simple *.geo file is attached.

Then I carry out mesh generation using gmsh, which consists of 1D meshing, following by 2D meshing:

gmsh-4.0.2: 1D meshing task takes 31.04 sec, and 2D meshing task takes 0.196 sec.
gmsh-3.0.6: 1D meshing task takes 0.28 sec, and 2d meshing task takes 0.276 sec.
 
Please realize this is a trivial example only to illustrate the differences between the two versions.
 
On real life examples where mesh boundary consists of thousands of nodes (in my examples of highly irregular coastlines), I have not been able to use gmsh-4.0.2 to produce 2D meshes at all. This is because the 1D meshing task takes simple too long to complete.
 
Has something changed in how gmsh-4.0.2 carries out 1D meshing? Perhaps there is a command to recover the previous 1D meshing algorithm?
 
I look forward to any comments and insights into the above,
 
Pat Prodanovic
 
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