Welcome to Deep Learning

An Interactive Journey from Artificial Intelligence to Neural Networks

AI
Machine Learning
Deep Learning

What is Deep Learning?

Deep learning is a subset of machine learning that uses neural networks with multiple layers to learn and make decisions from data, much like how the human brain processes information.

Artificial Intelligence

The broader field of making machines smart and capable of performing tasks that typically require human intelligence.

Examples: Chess programs, Expert systems
Machine Learning

A subset of AI that enables computers to learn and improve from experience without being explicitly programmed.

Examples: Logistic regression, Decision trees
Deep Learning

A subset of ML using neural networks with multiple layers to model and understand complex patterns in data.

Examples: CNNs, RNNs, Autoencoders
Simple Neural Network Example

# A simple neural network for binary classification
import numpy as np

def sigmoid(x):
    return 1 / (1 + np.exp(-x))

# Input data (4 examples, 3 features each)
X = np.array([[0,0,1], [0,1,1], [1,0,1], [1,1,1]])
# Output labels
y = np.array([[0], [1], [1], [0]])

# Initialize weights randomly
weights = np.random.uniform(size=(3,1))

# Training loop
for epoch in range(10000):
    # Forward pass
    output = sigmoid(np.dot(X, weights))

    # Calculate error
    error = y - output

    # Backward pass (gradient descent)
    adjustment = np.dot(X.T, error * output * (1 - output))
    weights += adjustment

print("Final weights:", weights.flatten())
                        

The Evolution of Deep Learning

1940s-1960s: Cybernetics Era

The birth of artificial neural networks with the McCulloch-Pitts neuron and the perceptron. Simple linear models that could recognize basic patterns.

Key: First learning algorithms, biological inspiration
1980s-1990s: Connectionism

Introduction of backpropagation algorithm, enabling training of multi-layer networks. Rise of distributed representations and parallel processing concepts.

Key: Backpropagation, multi-layer networks
2006-Present: Deep Learning Renaissance

Breakthrough with deep belief networks and layer-wise pretraining. Modern deep learning with CNNs, RNNs, and transformer architectures achieving human-level performance.

Key: Deep architectures, big data, GPU computing
Fun Fact

The term "deep learning" emphasizes the depth of neural networks - the number of layers between input and output. Modern networks can have hundreds of layers!

Core Concepts

Neural Network Architecture

Input Layer
x₁
x₂
x₃
Raw pixels
Hidden Layer 1
h₁
h₂
h₃
h₄
Edges
Hidden Layer 2
h₁
h₂
h₃
Corners & Contours
Hidden Layer 3
h₁
h₂
Object Parts
Output Layer
Car
Person
Object Identity

Each layer extracts increasingly abstract features from the input data

Why Representations Matter

Cartesian Coordinates

❌ Cannot separate with a line

Polar Coordinates

✅ Easy to separate with a line!

Key Insight: The same data can be impossible or trivial to work with depending on how it's represented. Deep learning automatically learns good representations!

The Big Data Revolution

Deep learning performance improves dramatically with more data

Real-World Examples

Computer Vision

Convolutional Neural Networks (CNNs) can identify objects, faces, and scenes in images with superhuman accuracy.

Natural Language Processing

Transformer models like GPT can understand and generate human-like text, translate languages, and answer questions.

Reinforcement Learning

AI agents learn to play games, control robots, and make decisions through trial and error, like AlphaGo.

Interactive Practice

Quiz: Test Your Understanding

Question 1: What is the main advantage of deep learning over traditional machine learning?

Neural Network Simulator

Adjust the parameters and see how they affect the network: