ppintegrate

Integration and ODE kernels, in POST Python.

ppintegrate reimplements scipy.integrate in POST Python — every kernel is fully-typed Python that runs under the standard CPython interpreter and compiles ahead-of-time to native code (a plain C shared library and a NumPy ufunc extension module) with the POST Python reference compiler.

Status: Planning — this repository is scaffolding, ready for an agent or contributor to claim. It is part of the PostSciPy effort to rebuild SciPy one subpackage at a time as the compiler's proving ground.

Primary compiler pressure this package generates: fixed-sample rules today; callable parameters for adaptive quadrature.

Start here

1. Read the POST Python spec and the PostSciPy roadmap (package map, working rules, capability matrix).
2. Copy the layout of ppspecial, the exemplar package: ppintegrate/ sources, tests/, scripts/build_native.py, scripts/build_ext.py, a pixi workspace with test / build-native / build-ext tasks, a git dependency on postpython, and a ROADMAP.md tracking targets and upstream requests.
3. Start with a slice from "Compiles today" below; land it as a small PR with tests in both execution modes.

First slices

Compiles today

• Fixed-sample rules as gufuncs: trapezoid and simpson (n),(n)->() (y, x) plus uniform-dx variants, romb, cumulative_trapezoid (n),(n)->(n)
• fixed_quad for low orders with Gauss-Legendre nodes as module constants

Blocked on compiler capabilities

File these as postpython issues with minimal reproducers when you start on them — the filing is part of the work and drives the compiler roadmap.

• quad / adaptive quadrature — needs callable parameters (co-lead the design with ppoptimize; file the postpython issue with a minimal reproducer)
• solve_ivp — callables plus result structs plus adaptive stepping

Working rules (summary)

• Pure POST Python: no compiler-specific escape hatches; every kernel runs interpreted and compiled.
• scipy is the reference, never a runtime dependency. Tests may use it optionally; prefer deterministic hardcoded reference values.
• Compiler gaps go upstream as postpython issues with reproducers, not silent workarounds.
• Verify against a postpython checkout on main.
• Document accuracy targets and reference sources per function.

The full rules and the definition of done live in the PostSciPy roadmap.