muoblpbindings

Performance-critical MOLP solver algorithms implemented in C++20, exposed to Python via pybind11. Built with scikit-build-core + CMake. 4th subproject of the multiobjective-lp monorepo; consumed by solvers as a path dependency.

Build requirements

• C++20 toolchain (gcc/clang/MSVC).
• Python >=3.13.
• CMake + Ninja: auto-provisioned by scikit-build-core during pip/poetry install (build isolation) — no manual install needed.
• pybind11 >=3, scikit-build-core >=0.12 (build-system deps, auto-fetched).

Build happens transparently on poetry install in solvers (path dep). No auto-rebuild on C++ edits — re-run install to rebuild.

macOS broken-CommandLineTools workaround

If bare clang++ can't find c++/v1 headers (broken CommandLineTools install):

export SDKROOT=$(xcrun --show-sdk-path)
export CXXFLAGS="-cxx-isystem $SDKROOT/usr/include/c++/v1"

Proper fix: reinstall CLT (xcode-select --install).

Core-model-shape contract

common.cpp reads the muoblp LpProblem (core) directly — bindings depend on this shape implicitly (no compile-time link to core):

• prob.objectives: list; each element has .name and is iterable as a dict {LpVariable: utility}. Utilities must be int — Utility is long long; pybind rejects float (non-dedup objective weights must be 1, not 1.0).
• prob.objectives_weights: dict[name -> double].
• prob.variables(), prob.constraints (first constraint = budget; budget = -constraint.constant, per-var cost from constraint dict).

Exposed functions

• equal_shares_utils(...), equal_shares_add1(...) — Method of Equal Shares.
• expanding_approvals(prob), single_transferable_vote(prob), solid_coalition_refinement(prob).

See src/muoblpbindings/__init__.pyi for signatures.

Adding new algorithm

1. Assuming algorithm is named x
2. Create x.cpp and x.hpp files with implementation
3. Bind method in binder.cpp
4. Define import and method signature in __init__.py and __init__.pyi
5. Add and link x.cpp as library in CMakeLists.txt
6. Bump project version in pyproject.toml

Publishing

Independent semver from the rest of the monorepo. Tag bindings@x.y.z (must match pyproject.toml version) triggers root .github/workflows/wheels.yml: sdist + cibuildwheel (ubuntu/macos-15/windows, cp313+cp314) → PyPI via OIDC. No rc/test.pypi route. workflow_dispatch runs a build-only dry run (upload skipped). Every PR additionally builds a linux wheel + import smoke test; solvers CI tests run against that artifact.