snn-samsit 0.1.2

Simple Neural Network — a pure-NumPy deep learning library with a Keras-like API

snn

A neural network / deep learning library built purely on NumPy — no TensorFlow, no PyTorch, no autograd. Every forward pass, backward pass, and weight update is implemented from scratch in vectorized NumPy.

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Install

pip install -e .

Or just drop the snn/ folder next to your script and import snn.

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Quickstart

from snn.model import Sequential
from snn.layers import Dense, Dropout, BatchNormalization
from snn.utils import to_categorical, train_test_split

# Build a model
model = Sequential([
    Dense(128, activation='relu'),
    BatchNormalization(),
    Dropout(0.3),
    Dense(64, activation='relu'),
    Dense(10, activation='softmax'),
])

# Compile
model.compile(
    optimizer='adam',
    loss='categorical_crossentropy',
    metrics=['accuracy'],
)

# Train
history = model.fit(
    X_train, y_train,
    epochs=20,
    batch_size=64,
    validation_data=(X_val, y_val),
)

# Evaluate
model.evaluate(X_test, y_test)

# Predict
y_pred = model.predict(X_test)

# Save / load weights
model.save_weights('my_weights')
model.load_weights('my_weights')

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What's Included

Layers

Layer	Description
Dense	Fully-connected layer
Conv2D	2D convolution (channels-last)
MaxPooling2D	Max pooling
AveragePooling2D	Average pooling
GlobalAveragePooling2D	Global average pool
GlobalMaxPooling2D	Global max pool
BatchNormalization	Batch norm (train/inference modes)
LayerNormalization	Layer norm
Dropout	Inverted dropout
SpatialDropout2D	Channel-wise dropout for feature maps
Flatten	Flatten to (N, -1)
Reshape	Reshape (excluding batch dim)
SimpleRNN	Vanilla RNN with BPTT
LSTM	Long Short-Term Memory
GRU	Gated Recurrent Unit

Activations

linear, relu, leaky_relu, elu, selu, sigmoid, tanh, softmax, softplus, swish, mish

Loss Functions

Loss	String key
Mean Squared Error	'mse'
Mean Absolute Error	'mae'
Huber	'huber'
Binary Cross-entropy	'binary_crossentropy'
Categorical Cross-entropy	'categorical_crossentropy'
Sparse Categorical CE	'sparse_categorical_crossentropy'
KL Divergence	'kl_divergence'

Optimizers

Optimizer	String key
SGD (+ momentum + Nesterov)	'sgd'
Adam	'adam'
AdamW	'adamw'
RMSprop	'rmsprop'
Adagrad	'adagrad'
Adadelta	'adadelta'

Initializers

zeros, ones, random_normal, random_uniform, glorot_uniform, glorot_normal, he_uniform, he_normal, lecun_uniform, lecun_normal

Metrics

accuracy, binary_accuracy, categorical_accuracy, sparse_categorical_accuracy, top_k_accuracy, precision, recall, f1_score, mse, mae, r2_score, confusion_matrix

Utilities

from snn.utils import (
    to_categorical,        # integer labels → one-hot
    normalize,             # min-max [0,1]
    standardize,           # zero mean, unit variance
    train_test_split,      # split arrays into train/test
    batch_generator,       # mini-batch iterator
    clip_gradients,        # global gradient norm clipping
    learning_rate_schedule,# exponential decay schedule
    cosine_annealing,      # cosine annealing schedule
    warmup_schedule,       # linear warmup + base schedule
    EarlyStopping,         # stop when metric stagnates
    ReduceLROnPlateau,     # reduce LR when metric plateaus
)

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Examples

python examples/xor_example.py          # XOR truth table
python examples/classification_example.py  # moons + blobs datasets
python examples/regression_example.py      # sin(x) + polynomial fitting

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Architecture

Every layer exposes:

• forward(x, training=False) — computes the output
• backward(grad) — computes and stores parameter gradients, returns input gradient
• params property — dict of trainable arrays
• grads property — dict of corresponding gradients

The Sequential model wires them together, calls optimizer.apply_gradients(params, grads) after each batch, and supports save_weights / load_weights via np.savez.

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Design Principles

• Pure NumPy — zero deep-learning framework dependencies
• Vectorized — all operations work on full batches; no Python loops over samples
• Keras-like API — familiar compile → fit → evaluate → predict interface
• Explicit gradients — every backward pass is hand-derived, making it a great learning resource