Floating-Point Comparisons without Tolerance in mesh_triangle_holes.C

[miaoyinb]

The find_intersection() function in mesh_triangle_holes.C contains a number of floating-point comparisons without tolerance. The function is used by MOOSE's XYDelaunayGenerator through libMesh::TriangulatorInterface::Hole::find_ray_intersections() to verify the holes/boundary geometry. And these floating-point comparisons without tolerance sometimes cause "false positive error" in such verification.