Deep Learning

Introduction

Deep Learning is a subset of machine learning, focusing on neural networks with many layers.

Neural Networks Basics

Feedforward Neural Network (FNN): The simplest type of neural network where information travels in one direction, from input to output.

Backpropagation: The main algorithm for weight updating in neural networks.

Activation Functions

  • Sigmoid;

  • ReLU (Rectified Linear Unit);

  • Tanh.

Training

Loss Functions:

  • Mean Squared Error (MSE): For regression problems.

  • Cross-Entropy Loss: For classification problems.

Epoch: One forward and backward pass of all training samples.

Batch Size: The number of training samples in one forward and backward pass.

Iterations: Number of passes, each pass using [batch size] number of samples.

Regularization

  • Dropout: Randomly sets a fraction of the input units to 0 at each update during training.

  • L1 & L2 Regularization: Adds a penalty to the loss function. L1 penalizes the absolute values of weights and L2 penalizes squared values.

Optimizers

  • Gradient Descent: Updates weights in the negative direction of the gradient.

  • Stochastic Gradient Descent (SGD): Same as gradient descent but updates are made after each training sample.

  • Adam: Combines the advantages of AdaGrad and RMSProp algorithms to provide an optimization algorithm that can handle sparse gradients.

Architectures

  • Convolutional Neural Networks (CNNs): Especially powerful for tasks like image recognition.

  • Recurrent Neural Networks (RNNs): Suitable for sequential data like time series or natural language.

  • Long Short-Term Memory (LSTM): A type of RNN that can remember long-term dependencies.

Frameworks

  • TensorFlow: Open-source software library for high-performance numerical computations.

  • Keras: High-level neural networks API, written in Python and capable of running on top of TensorFlow, CNTK, or Theano.

  • PyTorch: Open source machine learning library based on Torch, used for applications such as computer vision and NLP.

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