psann 0.9.8

PSANN: Parameterized Sine-Activated Neural Networks (sklearn-style, PyTorch backend)

PSANN — Parameterized Sine-Activated Neural Networks

Sklearn-style estimators powered by PyTorch. PSANN uses sine activations with learnable amplitude, frequency, and decay, plus optional persistent state for time series, conv variants that preserve spatial shape, and a segmentation head for per-element outputs.

• Docs: see TECHNICAL_DETAILS.md for math and design.

Features

• Sklearn API: fit, predict, score, get_params, set_params.
• SineParam activation: learnable amplitude/frequency/decay with stable transforms and bounds.
• Multi-D inputs: flatten automatically (MLP) or preserve shape with Conv1d/2d/3d PSANN blocks.
• Segmentation head: per-timestep/pixel outputs via 1×1 ConvNd head.
• Stateful time series: persistent per-unit amplitude-like state with bounded updates and controlled resets.
• Online streaming: step and predict_sequence_online with per-step target updates; separate stream_lr.
• Training ergonomics: verbose logging, validation, early stopping, Gaussian input noise, multiple losses (MSE/L1/Huber/SmoothL1) or custom callable.
• Save/load: torch checkpoints with estimator params and metadata.

Installation

python -m venv .venv
.\.venv\Scripts\Activate.ps1   # Windows PowerShell
# source .venv/bin/activate     # macOS/Linux
pip install --upgrade pip
pip install -e .                # editable install from source

• Optional plotting for examples: pip install .[viz]
• Optional scikit-learn integration (true BaseEstimator mixins): pip install .[sklearn]

Compatibility notes (NumPy/SciPy)

• Core package avoids a hard dependency on scikit-learn to reduce SciPy coupling. If you do not need scikit-learn utilities, you can skip installing it.
• NumPy is pinned below 2.0 (<2.0) for broad SciPy/scikit-learn wheel compatibility, especially on Windows. If you need newer stacks, ensure all deps support NumPy 2.x before upgrading.
• If you run into build/runtime errors on a fresh machine, try installing with the provided constraints:

pip install -e . -c requirements-compat.txt

These pins mirror widely available wheels on most platforms (similar to Colab defaults).

Quick Start

import numpy as np
from psann import PSANNRegressor

rs = np.random.RandomState(42)
X = np.linspace(-4, 4, 1000).reshape(-1, 1).astype(np.float32)
y = 0.8 * np.exp(-0.25 * np.abs(X)) * np.sin(3.5 * X) + 0.05 * rs.randn(*X.shape)

model = PSANNRegressor(
    hidden_layers=2,
    hidden_width=64,
    epochs=200,
    lr=1e-3,
    activation={"amplitude_init": 1.0, "frequency_init": 1.0, "decay_init": 0.1},
    early_stopping=True,
    patience=20,
)
model.fit(X, y, verbose=1)
print("R^2:", model.score(X, y))

Stateful Time Series (Streaming)

Train with one-step pairs, then stream predictions while preserving state. Use online updates to avoid compounding errors.

model = PSANNRegressor(
    hidden_layers=2,
    hidden_width=32,
    epochs=200,
    lr=1e-3,
    stateful=True,
    state={"rho": 0.985, "beta": 1.0, "max_abs": 3.0, "init": 1.0, "detach": True},
    state_reset="none",
    stream_lr=3e-4,
)
model.fit(X_train, y_train, validation_data=(X_val, y_val), verbose=1)

# Free-run over a sequence
free_preds = model.predict_sequence(X_test, reset_state=True, return_sequence=True)

# Online (per-step update using targets)
online_preds = model.predict_sequence_online(X_test, y_test, reset_state=True)

Multi-D Inputs and Segmentation

• Flattened MLP (default): (N, ...) -> (N, F).
• Preserve shape with conv PSANN: preserve_shape=True, data_format="channels_first|last".
• Per-element outputs: per_element=True swaps the global pooling head for a 1×1 ConvNd head.

# Channels-first images: (N, C, H, W)
X = np.random.randn(256, 1, 8, 8).astype(np.float32)
y = np.sin(X).astype(np.float32)  # per-pixel

model = PSANNRegressor(preserve_shape=True, data_format="channels_first", per_element=True,
                       hidden_layers=2, hidden_width=24, conv_kernel_size=3, epochs=20)
model.fit(X, y)
Yhat = model.predict(X[:4])      # (4, 1, 8, 8)

Optional LSM Preprocessor

You can pre-train a liquid-state-machine style expander to increase feature dimensionality before PSANN. The expander is trained to maximize OLS R^2 of reconstructing inputs from expanded features.

Note: when you pass an LSM (or LSMExpander) to PSANNRegressor(lsm=...), it is integrated into the model graph. Checkpoints saved via model.save(...) include the LSM weights; the lsm object itself is not pickled in params, but is reconstructed on load from saved weights and metadata.

from psann import LSMExpander, PSANNRegressor

X = ...  # (N, D)
lsm = LSMExpander(output_dim=256, hidden_layers=2, hidden_width=128, sparsity=0.9)
lsm.fit(X, epochs=50)

model = PSANNRegressor(hidden_layers=2, hidden_width=64, lsm=lsm, lsm_train=False)
model.fit(X_train, y_train)

# Jointly fine-tune LSM while training PSANN
model = PSANNRegressor(hidden_layers=2, hidden_width=64, lsm=lsm, lsm_train=True, lsm_lr=5e-4)
model.fit(X_train, y_train, validation_data=(X_val, y_val), verbose=1)

You can also pass a dictionary to lsm and PSANN will build the expander for you:

# Flattened path (LSMExpander)
model = PSANNRegressor(
    hidden_layers=2,
    hidden_width=64,
    lsm={
        "output_dim": 256,
        "hidden_layers": 2,
        "hidden_width": 128,
        "sparsity": 0.9,
        "nonlinearity": "sine",
        "epochs": 0,  # on-fit init OK
    },
)

HISSO (Episodic Strategy Optimization)

Some tasks (e.g., portfolio allocation) are better trained with episodic, horizon-informed sampling rather than supervised targets. PSANN integrates a “predictive extras” mechanism and HISSO training directly in fit().

import numpy as np
from psann import PSANNRegressor

prices = ...  # (T, M) series of asset prices
model = PSANNRegressor(hidden_layers=2, hidden_width=64, extras=2, epochs=60)
# HISSO: train over random windows of length 64; y is ignored
model.fit(prices, y=None, hisso=True, hisso_window=64, verbose=1)

# Roll out allocations and extras over the full series
alloc, extras = model.hisso_infer_series(prices)

Notes:

• extras adds K additional outputs after the M primary outputs and is internally handled during HISSO training.
• LSM can be provided as a pretrained module, an LSMExpander, or a dict of parameters and will be integrated automatically.

Input Scaling (supervised and HISSO)

Enable built-in input scaling by passing scaler at initialization:

# 'standard' (z-score) or 'minmax'; or pass any object with fit/transform
model = PSANNRegressor(hidden_layers=2, hidden_width=64, extras=2, epochs=60, scaler='standard')
model.fit(prices, y=None, hisso=True, hisso_window=64)

# At inference and during HISSO reward computation, PSANN automatically
# uses the inverse transform internally so portfolio metrics remain correct.

Custom scalers: pass an object implementing fit(X), transform(X), and optional inverse_transform(X) (sklearn-style). When calling fit() repeatedly, the internal scaler accumulates statistics across calls.

PSANN-LM (Language Model, experimental)

Train a simple language model that predicts next-token embeddings using a PSANN core.

Key ideas:

• Tokenization: pass a tokenizer or use SimpleWordTokenizer.
• Embedding: pass a pretrained SineTokenEmbedder or let the model create one.
• Objective: episodic next-token prediction with MSE between predicted and target embeddings.
• Decoding: nearest neighbor in embedding space (cosine similarity) to recover the next token.
• Training: supports periodic perplexity reporting and a simple curriculum.

Quick start:

from psann import PSANNLanguageModel, LMConfig, SimpleWordTokenizer, SineTokenEmbedder

corpus = [
    "the quick brown fox jumps over the lazy dog",
    "dogs bark and foxes dash swiftly",
]

tok = SimpleWordTokenizer()
emb = SineTokenEmbedder(embedding_dim=32)
cfg = LMConfig(embedding_dim=32, extras_dim=0, episode_length=16, batch_episodes=16)
lm = PSANNLanguageModel(tokenizer=tok, embedder=emb, lm_cfg=cfg, hidden_layers=2, hidden_width=64)

lm.fit(
    corpus,
    epochs=50,
    lr=1e-3,
    ppx_every=5,                      # print perplexity
    curriculum_type="progressive_span", # simple curriculum
    curriculum_warmup_epochs=10,
    curriculum_min_frac=0.2,
    curriculum_max_frac=1.0,
)

print("Next token:", lm.predict("the quick"))
print("Generate:", lm.gen("the", max_tokens=8))

lm.save("psann_lm.pt")
lm2 = PSANNLanguageModel.load("psann_lm.pt")
print(lm2.gen("the", max_tokens=8))

Notes:

• Perplexity is estimated from cosine-similarity softmax over the embedding matrix (temperature adjustable via ppx_temperature).
• Curriculum ("progressive_span") limits sampled episode starts to a growing fraction of the token stream over the specified warmup.