Initial release: precompiled Linux x86_64 / CPython 3.12 binary + Python wrapper

OpenMP-parallel numerical kernel library.  No build step required at
install: drop-in shared object plus thin numpy-facing wrapper.

Contents:
  - sem_cython12/sem_core12.cpython-312-x86_64-linux-gnu.so
  - sem_cython12/wrapper.py
  - sem_cython12/__init__.py
  - requirements.txt
  - README.md
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# sem_cython12
OpenMP-parallel numerical kernel library for Python. Pre-built Linux
shared object included; no compilation required at install time.
## Contents
- `sem_cython12/sem_core12.cpython-312-x86_64-linux-gnu.so` -
compiled extension (Linux, CPython 3.12, x86_64).
- `sem_cython12/wrapper.py` - Python API.
- `sem_cython12/__init__.py` - package entry.
## Requirements
- Linux x86_64.
- CPython 3.12.
- numpy >= 1.23 (see `requirements.txt`).
- A modern glibc + libgomp. Both ship with Ubuntu 20.04 LTS and
later. No other system libraries needed.
The Windows / macOS binaries are not included in this distribution.
## Install
```bash
git clone https://git.sevana.biz/vvs/sem_cython12.git
cd sem_cython12
pip install -r requirements.txt
# Make the package importable, either:
pip install -e . # if pyproject.toml/setup.py is added
# or just put the package on PYTHONPATH:
export PYTHONPATH=$PWD:$PYTHONPATH
```
## Quick start
```python
import numpy as np
from sem_cython12 import wrapper as cy
# Sanity check
assert cy.available(), "compiled extension did not load"
print("backend:", cy.backend())
# Thread count (defaults to ~50% of logical cores; set explicitly via
# either the SEM_NUM_THREADS env var or set_num_threads()):
cy.set_num_threads(8)
print("threads:", cy.get_num_threads())
# Example workload
rng = np.random.default_rng(0)
Q = rng.standard_normal((1000, 32)) # 1000 queries
M = rng.standard_normal((5000, 32)) # 5000 reference points
# For each query: max similarity to any reference, with kernel scale lam.
sim = cy.batch_max_similarity(Q, M, lam=1.0)
print(sim.shape, sim.dtype) # (1000,) float64
```
## API reference
All functions accept either Python lists or numpy arrays; inputs are
internally cast to contiguous `float64`. Outputs are numpy arrays.
### Configuration
| Function | Purpose |
|---|---|
| `available() -> bool` | True iff the compiled extension loaded |
| `backend() -> str` | `'cython12'` or `'python-fallback'` |
| `get_num_threads() -> int` | Active OpenMP worker count |
| `set_num_threads(n: int)` | Set OpenMP worker count (n >= 1) |
### Distance / similarity
| Function | Inputs | Output |
|---|---|---|
| `batch_max_similarity(X_query, X_members, lam)` | `(Q, D)`, `(M, D)`, `lam > 0` | `(Q,)` - per-query max of `exp(-d / lam)` |
| `concept_support_matrix(X_query, member_mats, lam)` | `(Q, D)`, list of `(M_k, D)`, `lam > 0` | `(Q, K)` - one column per member matrix |
| `pairwise_distances(X)` | `(N, D)` | `(N, N)` - symmetric Euclidean matrix |
| `nn_distances(X)` | `(N, D)` | `(N,)` - min positive distance per row; `inf` if none |
### Pareto / dominance
| Function | Inputs | Output |
|---|---|---|
| `pareto_core_mask(S)` | `(N, k)` | `(N,)` byte mask: `1` iff row not strictly dominated |
| `one_sided_mask(S)` | `(N, k)` | `(N, k)` byte mask: see docstring |
| `non_redundant_witnesses(S)` | `(N, k)` | int32 array of row indices |
### Vector reduction
| Function | Inputs | Output |
|---|---|---|
| `extend_frontier_kernel(cur_centers, cur_radii, new_emb, cur_arity)` | `(F, D)`, `(F,)`, `(A, D)`, `int` | `(flat_centers (F*A, D), flat_radii (F*A,))` |
See the wrapper docstrings for exact semantics of each function.
## Performance notes
Threads are configured globally per process; calling
`set_num_threads(n)` updates the OpenMP team size for all subsequent
calls. The default uses approximately 50% of the host's logical
cores so other processes are not starved on shared machines.
For workloads dominated by `pairwise_distances` and
`pareto_core_mask`, near-linear scaling up to ~8 threads is typical
on commodity x86 hardware. `batch_max_similarity` is BLAS-friendly
and benefits most from larger `M` (reference set) at fixed `D`.
## Memory / threading model
- All arrays are processed in shared memory; no inter-process
serialisation.
- Each routine releases the GIL during its inner loops, so calling
it concurrently from Python threads is safe.
- The compiled extension links against the system OpenMP runtime
(`libgomp`); avoid mixing with conda's `intel-openmp` in the same
process if possible.
## Diagnostics
`backend()` returns `'python-fallback'` only when the `.so` failed
to import (wrong architecture, glibc too old, missing libgomp). In
that state, every numerical function raises `RuntimeError`; check
`available()` before each batch to fail loudly rather than silently
fall back.
## Licence
Proprietary. Internal use only.
## Support
Open an issue at https://git.sevana.biz/vvs/sem_cython12.