README.md

digits-nn

This is my implementation of a neural network for identifying handwritten digits from the MNIST dataset.
https://deepai.org/dataset/mnist

The nalgebra crate is used for linear algebra.

Some of the code is somewhat spaghetti-ish at the moment.

Network info

Softmax activation is used for the output layer; ReLU activation is used for all other layers. The cost function used is categorical cross-entropy.

Momentum and Nesterov accelerated gradient as described here are used for learning optimization.

The repository additionally includes a gradient check function that uses the functionality described here.

The values I used for the following configurable parameters are:

• hidden layers: 40 and 16 neurons
• learning rate: 0.01
• momentum decay: 0.9
• batch size: 300
• epochs: 10

Usage

Build

cargo build --release

The RON format is used for configuration.

Invoking the binary will attempt to load a file named network from the current directory, and initialize a network with random weights and zeroed biases if no existing network is found.

Invoking without arguments will train the network based on the config from a file named config.ron in the current directory.
A thread pool is used to increase training speed.

Invoking with the --test argument will run the network on the entire test dataset, keeping track of average cost and accuracy.

The format of the configuration file is as follows:

• data: locations of data
  • train: training data
    • labels: training labels file
    • images: training images file
  • test: testing data
    • labels: testing labels file
    • images: testing images file
• h_layers: array representing neuron counts in hidden layers
• learning_rate: coefficient of gradient descent steps (0–1)
• momentum_decay: coefficient of decaying momentum (0–1)
• batch_size: number of samples for each gradient descent step
• epochs: number of times the entire training set is repeated