Neural Networks: From Fundamentals to Modern AI · Your First End-to-End Training — From Data to Prediction
XOR classifier in pure NumPy — a 2-2-1 network from scratch
Your First End-to-End Training — From Data to Prediction
Introduction
Putting it all together: data, forward, loss, gradient, update. We implement the classic XOR-solving network in pure NumPy — no PyTorch, no TensorFlow, no magic. You will see exactly where every matrix is computed, how the chain rule "flows" through layers, why XOR is unsolvable without a hidden layer, and how after a few thousand epochs the network learns the four patterns. After this lesson you understand what PyTorch is doing for you under the hood.