Add General.NumThreads = CPU core count setting to Gmsh

settings file to enable multi-threaded meshing (much faster
for larger models)

src/Mod/Fem/femmesh/gmshtools.py

@@ -733,6 +733,13 @@ class GmshTools():
         geo = open(self.temp_file_geo, "w")
         geo.write("// geo file for meshing with Gmsh meshing software created by FreeCAD\n")
         geo.write("\n")
+
+        cpu_count = os.cpu_count()
+        if cpu_count != None and cpu_count > 1:
+            geo.write("// enable multi-core processing\n")
+            geo.write(f"General.NumThreads = {cpu_count};\n")
+            geo.write("\n")
+
         geo.write("// open brep geometry\n")
         # explicit use double quotes in geo file
         geo.write('Merge "{}";\n'.format(self.temp_file_geometry))

src/Mod/Fem/femtest/app/support_utils.py

@@ -228,17 +228,21 @@ def compare_files(
     file1 = open(file_name1, "r")
     f1 = file1.readlines()
     file1.close()
+
+    # TODO: add support for variable values in the reference file
+    # instead of using this workaround
+
     # workaround to compare geos of elmer test and temporary file path
     # (not only names change, path changes with operating system)
     lf1 = [l for l in f1 if not (
-        l.startswith('Merge "') or l.startswith('Save "') or l.startswith("// ")
+        l.startswith('Merge "') or l.startswith('Save "') or l.startswith("// ") or l.startswith("General.NumThreads")
     )]
     lf1 = force_unix_line_ends(lf1)
     file2 = open(file_name2, "r")
     f2 = file2.readlines()
     file2.close()
     lf2 = [l for l in f2 if not (
-        l.startswith('Merge "') or l.startswith('Save "') or l.startswith("// ")
+        l.startswith('Merge "') or l.startswith('Save "') or l.startswith("// ") or l.startswith("General.NumThreads")
     )]
     lf2 = force_unix_line_ends(lf2)
     import difflib

src/Mod/Fem/femtest/data/elmer/group_mesh.geo

@@ -1,5 +1,8 @@
 // geo file for meshing with Gmsh meshing software created by FreeCAD
 
+// enable multi-core processing
+General.NumThreads = X;
+
 // open brep geometry
 Merge "/tmp/tmp0TVZbM.brep";