modern-fm 0.4.0

Fast, sklearn-compatible Factorization Machines and Field-aware Factorization Machines

modern_fm

Fast, sklearn-compatible Factorization Machines (FM) and Field-aware Factorization Machines (FFM) for Python.

Status: v0.3 (Beta). A Rust CPU backend (parity-tested against pure-NumPy reference implementations) drives sklearn-style estimators — FMClassifier (binary + multiclass softmax), FMRegressor, and FFMClassifier (binary + multiclass softmax) — with the SGD / AdaGrad / Adam / FTRL-Proximal optimizers, mini-batch gradient averaging (batch_size), multi-core training via rayon (n_jobs), plus sample_weight/class_weight, label_smoothing, early stopping, a CategoricalEncoder, and save_model/load_model. FTRL's L1 (l1_linear/l1_factors) yields exact-zero weights. The estimators are scikit-learn check_estimator-compatible (drop into Pipeline / GridSearchCV), accept pandas / polars DataFrames, and load_libffm / dump_libffm read and write the libffm text format. See docs/roadmap.md for remaining niche gaps (FTRL + early stopping, multiclass + early-stopping for FFM).

Installation

pip install modern-fm        # prebuilt wheels for Linux/macOS/Windows, no Rust toolchain needed

To build from source instead (e.g. on a platform without a prebuilt wheel), see Development below; it requires a Rust toolchain.

Usage

from modern_fm import FMClassifier, FFMClassifier

model = FMClassifier(
    n_factors=16,
    optimizer="adagrad",
    learning_rate=0.05,
    max_iter=100,
    batch_size=256,        # mini-batch gradient averaging (1 = per-row SGD)
    n_jobs=-1,             # train batches across all CPU cores
    l2_linear=1e-5,
    l2_factors=1e-5,
    random_state=42,
)
model.fit(X_train, y_train)
proba = model.predict_proba(X_test)

# FTRL-Proximal with L1 for sparse linear weights (classic CTR setup)
sparse = FMClassifier(optimizer="ftrl", l1_linear=1.0, batch_size=256, random_state=42)
sparse.fit(X_train, y_train)

ffm = FFMClassifier(n_factors=8, n_jobs=-1, random_state=42)
ffm.fit(X_train, y_train, field_ids=field_ids)

FMRegressor, multiclass FMClassifier (just pass a target with >2 classes), early stopping (early_stopping=True or eval_set=(X_val, y_val)), and the CategoricalEncoder are demonstrated in examples/basic_usage.py. benchmarks/bench_synthetic.py reports fit time and predict throughput against the NumPy reference floor.

Benchmarks

On synthetic CTR data (40k train / 20k test; 16 one-hot categorical fields → 256 features) with planted pairwise interactions between field pairs — signal a linear model cannot represent — FM/FFM recover most of it. n_jobs=-1 uses all cores (8 here); absolute numbers vary by machine.

Model	Test AUC	Fit (s)	Predict (rows/s)
LogisticRegression (sklearn)	0.694	0.01	60M
FMClassifier (batch=1)	0.817	1.34	4.3M
FMClassifier (batch=512)	0.816	0.45	4.8M
FMClassifier (batch=512, n_jobs=-1)	0.816	0.33	5.0M
FFMClassifier (batch=512)	0.846	1.68	2.3M
FFMClassifier (batch=512, n_jobs=-1)	0.846	1.46	2.1M

• Interactions matter: AUC climbs 0.69 → 0.82 (FM) → 0.85 (FFM) as the model captures the pairwise / field-aware structure the linear baseline misses.
• Mini-batch: batch_size=512 trains ~3× faster than per-row SGD at equal AUC.
• Multi-core: n_jobs=-1 adds a further ~1.2–1.4× here (more on larger/denser data).

Reproduce with python benchmarks/bench_vs_baseline.py. xlearn is auto-included if importable, but it does not build on every platform (it failed to build here on macOS/arm64 + CPython 3.11).

Development

Requires Python >= 3.10 and a recent Rust toolchain (1.74+; rustup update).

python3 -m venv .venv
.venv/bin/pip install -e ".[dev]"   # builds the Rust extension via maturin
.venv/bin/pytest -q
.venv/bin/ruff check .

pip install -e . compiles rust/ and installs the extension as modern_fm._rust (maturin mixed layout, config in pyproject.toml). After editing Rust code, re-run pip install -e . to rebuild. Rust-only checks:

cd rust
PYO3_PYTHON=$PWD/../.venv/bin/python3 cargo test
PYO3_PYTHON=$PWD/../.venv/bin/python3 cargo clippy

Without the extension built, the package still works: modern_fm._backend falls back to the pure-NumPy reference implementations, and the parity tests in tests/test_rust_parity.py are skipped.

Design documents live in docs/ — start with docs/requirements.md and docs/math_spec.md. The roadmap is in docs/roadmap.md.