Test for reading 2nd-order gmsh meshes into PETSc

quadratic-disc-test.py

import subprocess
from petsc4py import PETSc

geo_text = """
Point(1) = {0, 0, 0, 1.0};
Point(2) = {-0.5, -0, 0, 1.0};
Point(3) = {0, -0.5, 0, 1.0};
Point(4) = {0, 0.5, 0, 1.0};
Point(5) = {0.5, -0, 0, 1.0};
Characteristic Length { 1,2,3,4,5 } = 0.25;

Circle(1) = {2, 1, 3};
Circle(2) = {3, 1, 5};
Circle(3) = {5, 1, 4};
Circle(4) = {4, 1, 2};
Line Loop(5) = {4, 1, 2, 3};
Plane Surface(6) = {5};

Physical Surface("MyDisk") = {6};
Physical Line("Bdry") = {4, 1, 2, 3};
"""

with open("disc.geo", "w") as geo_file:
    geo_file.write(geo_text)

command = "gmsh -2 -order 2 -v 0 -o disc.msh disc.geo"
subprocess.run(command.split())

viewer = PETSc.Viewer().create()
viewer.setType("ascii")
viewer.setFileMode("r")
viewer.setFileName("disc.msh")
plex = PETSc.DMPlex().createGmsh(viewer)
dm = plex.getCoordinateDM()
section = dm.getSection()
print(f"Depth strata: {[plex.getDepthStratum(k) for k in [0, 1, 2]]}\n")
section.view()