What is early stopping?

What is early stopping? Early stopping is a technique used during the training of machine learning models to prevent overfitting. Instead of training for a fixed number of epochs, early stopping monitors the model’s performance on a validation set and halts training when performance begins to degrade. For example, if a model’s validation error stops improving or starts increasing, training is stopped early to avoid memorizing noise or irrelevant patterns in the training data. This approach balances model complexity by ensuring training doesn’t continue past the point of diminishing returns.

How does it work in practice? During training, metrics like loss or accuracy are tracked on both the training and validation datasets. A common implementation involves setting a threshold (called “patience”) that determines how many epochs to wait for improvement before stopping. For instance, if patience is set to 3, training continues until the validation loss fails to improve for three consecutive epochs. At that point, the model’s weights are reverted to the best-performing checkpoint. Tools like TensorFlow or PyTorch provide callback functions (e.g., EarlyStopping in Keras) to automate this process. Developers can customize metrics, patience, and whether to restore the best weights.

When should you use early stopping? Early stopping is particularly useful when training computationally expensive models (e.g., deep neural networks) or working with limited data where overfitting is a high risk. It reduces the need to manually guess the optimal number of epochs and saves resources by stopping unnecessary training. However, it requires a representative validation set—poorly split data can lead to premature stopping or missed improvements. While effective, it’s often combined with other regularization methods like dropout or weight decay for better results. For example, training a text classifier on a small dataset might use early stopping alongside dropout layers to prevent both overfitting and wasted computation.