Hi Pat, Thanks for the report and the test case. For some reason the smaller step size we introduced in Gmsh 4 in the finite difference approximation of the derivative of curve parametrizations leads to some numerical instability. I have reverted the value back to the one used in Gmsh 3: the next snapshot will contain the change.
@all : let us know if you see any adverse side effects from this change on other cases. (It will only affect geometries built with the "built-in" CAD kernel.) Christophe > On 15 Oct 2018, at 17:09, Pat Prodanovic <[email protected]> wrote: > > 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 > > <mesh.geo>_______________________________________________ > gmsh mailing list > [email protected] > http://onelab.info/mailman/listinfo/gmsh — Prof. Christophe Geuzaine University of Liege, Electrical Engineering and Computer Science http://www.montefiore.ulg.ac.be/~geuzaine Free software: http://gmsh.info | http://getdp.info | http://onelab.info _______________________________________________ gmsh mailing list [email protected] http://onelab.info/mailman/listinfo/gmsh
