group_reduce()

[flexatone]

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[Copilot]

Pull request overview

Adds a new group_reduce() API to ArrayKit’s C extension for fast per-group reductions over dense factorized codes, exposing it through the Python package and validating behavior via a dedicated test suite.

Changes:

• Implement group_reduce() in src/methods.c and export it via the extension module method table.
• Expose group_reduce() in the Python package (__init__.py) and type stubs (__init__.pyi).
• Add unit tests covering basic behavior, dtype handling, NaN propagation, immutability, equivalence to NumPy, and error cases.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/test_group_reduce.py	Adds unit tests for group_reduce() across ops, dtypes, NaN behavior, and error handling.
src/methods.h	Declares the new group_reduce C-extension entry point.
src/methods.c	Implements grouped reductions for float64/int64 and count, with input validation and immutable outputs.
src/_arraykit.c	Registers group_reduce in the module method table.
src/init.pyi	Adds the public typing stub for group_reduce.
src/init.py	Exposes group_reduce at the package top level.
README.rst	Documents group_reduce() under “What is New”.

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