BRepGProp.SurfaceProperties is the hottest kernel call the app makes — 94 % of
face_candidate_anchors, 0.99 s of 1.05 s for 690 faces — not because the kernel
is slow but because it is reached once per face from Python, so a rebuild pays
the round-trip hundreds of times per feature over a growing shape.
face_surface_props(shape, *, parallel=True, eps=None) runs the whole scan
C++-side with the GIL released, optionally over OSD_Parallel, and returns
(areas[F], centroids[F,3]) in MapShapes(FACE) order — the face identity the
topology layer already keys on, so a caller indexes straight into it. A face
OCCT cannot integrate reports zeros, matching what the app's own try/except
substitutes.
Tested against the same stock-recorded per-face reference the Inc 1 gate uses,
and against the one-call-per-face loop it replaces. Parallel and serial are
compared with array_equal rather than approx: the parallel path shares one
TopoDS_Shape across threads, so an exact match is the evidence that nothing
reachable from it gets mutated while measuring.
Backend adoption comes after the cutover, so this changes nothing yet.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DfriM8XUkn7uYf5Dwe2xo6
Builds n3xd-ocp end to end and publishes 7.9.3.1.dev1 to the Gitea registry,
where it installs anonymously and passes its suite.
- occt/Dockerfile: OCCT 7.9.3 compiled once into a manylinux_2_28 builder
image (base digest + tarball sha256 pinned), Draw/VTK/Tk/Xlib/OpenGL off,
FreeType on, -O2 without fast-math or march=native. A final layer asserts
TKService/TKV3d exist with no libGL/libX11 DT_NEEDED, which is what lets the
app image drop libgl1/libx11-6. Mounted into, never built FROM.
- scikit-build-core + nanobind STABLE_ABI -> one cp312-abi3 extension that
registers every OCP.* submodule via PyImport_AddModule, so `import
OCP.TopoDS` needs no shim and cls.__module__ is right. Version <occt>.N is
asserted against the OCCT found, keeping occt_version() truthful.
- occt_handle.h: type caster for opencascade::handle<T> over OCCT's intrusive
refcount. Wrappers are non-owning instances holding exactly one handle in
their keep-alive list, reusing an existing wrapper so identity survives a
round trip. Transient constructors go through ocp_new (never nb::init<>,
which would let OCCT delete nanobind's storage); the caster refuses a
refcount-0 object rather than corrupt the heap. Verified under ASAN with no
memory-safety errors, plus an RSS bound over 50k create/destroy cycles.
- Sub-shapes are returned by value everywhere, making the TShape lifetime class
that segfaulted a process-global face memo unrepresentable.
- Standard_Failure derives RuntimeError, with ~20 concrete types dispatched on
the dynamic OCCT type (cad_pool marshals failures home by type name).
- Inc 0 surface: gp subset, TopAbs, TopoDS (+ downcasts), TopExp, TopLoc,
TopTools, BRep, BinTools, Poly, Standard. 34 of the app's 139 symbols.
- n3xd_ocp: additive APIs kept out of the OCP namespace so parity testing stays
meaningful. bintools (shape <-> bytes, GIL-free, byte-identical) and _debug.
Two findings worth the record, both verified against the stock wheel rather
than assumed: upstream binds __hash__ but leaves __eq__ at identity, which is
exactly what geom_memo.py's hash-bucket + IsSame scan is built around, so we
match it instead of "fixing" it; and BinTools can release the GIL after all, by
slurping the file-like object instead of bridging a streambuf that would call
back into Python.
Gate: BREP round-trips are byte-identical to cadquery-ocp-novtk across six
fixtures (the generator asserts stock idempotency first). That matters beyond
IPC — derive.py content-addresses BREP payloads by sha256 and stores the ref.
