Nanobind migration discussion #101

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1. vincefn

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   issue type on Aug 12, 2026
2. vincefn

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3. sbillinge commented on Aug 13, 2026

   

   sbillinge

   on Aug 13, 2026

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   Thanks @vincefn this is super-helpful. We haven't formulated specific standards for this migration and so lessons learned and recommendations from you are super helpful. As a general issue, moving to pyproject.toml/cmake builds seems like it is taking us in the right direction. I don't think there is any downside for us to drop scons, but as I said, I don't have tons of experience with that. Also, getting rid of the extra layer of libobjcryst seems like a win, so I don't object to that at all.

   I will read the notes in detail with my c++ enabled folks and see if they have any feedback.
4. vincefn commented on Sep 1, 2026

   

   vincefn

   on Sep 1, 2026

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   nanobind branch update (September 2026)

   The nanobind_migration_test branch has been updated and is now based on the current main HEAD.

   What was done

   Submodule update

   • extern/objcryst updated from bfdcfda → 30fc8df (8 new upstream commits), adding GetRwHistory, minRwpVar, ReflectionProfilePseudoVoigtTCH, PowderPatternBackgroundHist, aniso PV constructor fix, etc.

   Translated from main branch commits (boost.python → nanobind):

   • PR makeNdArray: return pyarray directly instead of bp::incref  #108: makeNdArray memory fix — N/A for nanobind (no bp::incref)
   • PR Add lsq.GetVarianceCovarianceMap() #109: lsq.GetVarianceCovarianceMap() → dict keyed by (param_name, param_name) tuples
   • PR Fix EraseAllParamSet binding for compiled RefinableObj #110: EraseAllParamSet fix on compiled RefinableObj — already correct in nanobind via lambda; added test
   • PR Expose objcryst's anisotropic Pseudo-Voigt reflection profile #112: Expose ReflectionProfilePseudoVoigt and ReflectionProfilePseudoVoigtAnisotropic as constructible classes; add IsAnisotropic() to base
   • PR Expose PowderPatternDiffraction.X2XCorrPhase #114: PowderPatternDiffraction.X2XCorrPhase()

   Translated from open PRs (#107, #113, #115, #116):

   • PR Add method GetRwHistory to lsq #107: lsq.GetRwHistory() → list[float] of per-cycle Rw values
   • PR Add Rwp threshold minRwpVar for lsq.Refine() #113: minRwpVar argument added to lsq.Refine() and lsq.SafeRefine()
   • PR Add profile ReflectionProfilePseudoVoigtTCH with TCH instead of explicit Eta mixing #115: ReflectionProfilePseudoVoigtTCH (TCH implicit-eta profile) with 8-parameter SetProfilePar()
   • PR Make LSQ.PrepareRefParList silent by default via new verbose argument #116: verbose overload for LSQ.PrepareRefParList()

   Bug fixes in nanobind bindings:

   • Fixed pre-existing build error in nb_crystal.cpp: replaced non-existent nb::detail::keep_alive() free function (nanobind 3.x) with nb::keep_alive<1,2>() annotation
   • CMakeLists.txt: added homebrew include paths for Boost headers on macOS
   • Added SetProfile() to PowderPatternDiffraction (needed to install concrete profile objects)

   Tests: 171 tests, all passing.

   👍React with 👍1Reacted by Clemens Schmid
5. vincefn commented on Sep 24, 2026

   

   vincefn

   on Sep 24, 2026

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   Nanobind migration update:

   • Synced the migration branch with the latest main changes from Add method GetRwHistory to lsq #107, Add Rwp threshold minRwpVar for lsq.Refine() #113, Add profile ReflectionProfilePseudoVoigtTCH with TCH instead of explicit Eta mixing #115, and Make LSQ.PrepareRefParList silent by default via new verbose argument #116.
   • Ported and verified LSQ.GetRwHistory(), minRwpVar for Refine()/SafeRefine(), ReflectionProfilePseudoVoigtTCH, and silent-by-default PrepareRefParList(verbose=False) in the nanobind bindings.
   • Removed the libobjcryst and libboost-python dependencies. ObjCryst++ is vendored and built statically; only Boost headers remain required.
   • Built a wheel from the updated checkout and ran the complete suite: 172 tests passed. Existing nanobind reference-leak diagnostics still appear at interpreter shutdown.