Techniques to prevent overfitting by constraining model complexity during training.Regularization methods are techniques used in machine learning to prevent overfitting by constraining model complexity during training. Overfitting occurs when a model learns the noise in the training data rather than the underlying pattern, leading to poor performance on new data. Regularization adds a penalty term to the loss function, discouraging the model from becoming too complex. Common methods include L1 (Lasso) and L2 (Ridge) regularization, which shrink weights toward zero, and dropout, which randomly disables neurons during training.
Regularization methods have roots in classical statistics, with ridge regression introduced by Arthur Hoerl and Robert Kennard in 1970, and Lasso by Robert Tibshirani in 1996. Dropout was introduced by Geoffrey Hinton and colleagues in 2012.
The core idea is to add a term like λ·R(θ) to the loss function, where R(θ) measures model complexity (e.g., sum of squared weights for L2, sum of absolute weights for L1). The hyperparameter λ controls the strength of regularization. During gradient descent, the penalty forces the model to find simpler solutions that generalize better. Dropout works by randomly setting a fraction of activations to zero each training step, effectively training an ensemble of smaller networks and reducing co-adaptation of neurons.
Regularization is used in virtually all modern neural network training, including image recognition, natural language processing, and scientific applications like predicting material properties or analyzing medical images.
Dropout was inspired by sexual reproduction: the idea that genes should not rely on each other too much, similar to how neurons should not co-adapt.




















