Improve clipping code performance

[gunney1]

Summary

• This PR is a feature. It does the following:

  • Adds geometry-specific optimizations for the mesh clipping.
  • Extends the MeshClipper test with the new geometries.

• The following new classes implement the MeshClipperStrategy interface:

  • PlaneClipper for a plane geometry
  • TetClipper for a tetrahedron
  • HexClipper for a hexahedron
  • SphereClipper for a sphere
  • FSorClipper for a surface of revolution where the discrete curve r(z) is a function. Although the curve may have vertical segments, it may not double back in z. It can support stepped geometries but not hollow geometries. Cones and cylinders are supported by this implementation.
  • SorClipper for surface of revolution where the r(z) curve can double back on itself, for example to make a bowl.
  • TetMeshClipper for a general geometry described by a tetrahedral mesh.

• New code are in namespace experimental, because this is still a work in progress.

Dependencies

The mesh clipping refactor includes multiple PRs. Please review these before this one.

• Fix crash querying whether an exec space uses an allocator id. #1661
• Extend primal geometries for clipping re-factor #1662
• Feature/gunney/extend klee geometry #1666
• Initial clipping code re-factor #1667

Image of geometries supported (excluding the plane clipper)

Performance comparison

This is a comparison of clipping times for the IntersectionShaper and the MeshClipper, showing the wall time it took to clip a sample of geometries. It uses the quest_shape_in_memory example for the IntersectionShaper and the quest_mesh_clipper test for the MeshClipper. The tests are run on the CPU on rzwhippet and on the GPU on rzadams. The mesh is 30^3 for the CPU and 100^3 for the GPU. Most of the geometries occupy about 1/16 of the mesh. Note that performance is highly configuration dependent, so this data does not tell the whole story. Furthermore, the amortization of shared costs in the new code was not used.

rzwhippet + seq, 30³ mesh

Code	plane	tet	tetmesh	hex	sphere	cyl	cone	sor
IntersectionShaper	5.66	0.74	0.88	1.19	6.43	26.4	21.5	8.76
MeshClipper	0.02	0.08	0.33	0.30	0.76	3.93	4.69	6.20

rzadams + hip, 100³ mesh

Code	plane	tet	tetmesh	hex	sphere	cyl	cone	sor
IntersectionShaper	.90	.48	.48	.53	.93	3.31	2.65	1.29
MeshClipper	.10	.33	.38	.37	.66	.50	.58	.62