Clipping

See also: Machine learning terms

Introduction

Clipping is a technique employed in machine learning to prevent the weights of a neural network from growing too large during optimization. Excess weights can lead to instability during training, causing the network to diverge and fail to converge on an optimal solution.

The Need for Clipping

Machine learning algorithms like stochastic gradient descent (SGD) are commonly employed to update the weights of a neural network during training. SGD works by computing the gradient of the loss function with respect to the network's weights and adjusting them in the direction of that negative gradient in order to minimize loss. However, if this gradient is very large, it could cause weights to change rapidly, leading to unstable behavior.

This problem is especially prevalent in deep neural networks, which can have millions of weights that make it difficult to keep them under control during training. Clipping offers a straightforward solution by restricting the range of the weights and preventing them from growing too large.

How Clipping Works

Clipping involves setting a maximum threshold for the norm of the gradient of the loss function with respect to weights. Usually, this value is set to something small like 1.0 or 5.0 so that weights do not change too much during each update.

When the gradient exceeds a threshold, it is scaled down so its norm equals the threshold. This reduces the magnitude of the change and limits how far weights can move. The amount by which this scaling takes place is determined by a scaling factor which balances competing objectives of keeping weights from becoming too large while still ensuring an acceptable learning rate.

Clipping can be applied to both the gradients computed by the optimizer and weights themselves. When applied to weights, clipping ensures they remain within a specified range, avoiding them from becoming too large or small. This helps regulate the network and prevent overfitting.

Types of Clipping

Machine learning applications may benefit from various clipping techniques, such as:

1. L2 Clipping: the norm of the gradient is clipped using L2 normalization, which involves dividing the gradient by its L2 norm.
2. L1 Clipping: the norm of the gradient is clipped using L1 normalization, which involves dividing the gradient by its L1 norm.
3. Gradient Clipping: Gradient clipping involves scaling the gradient if its norm exceeds a specified threshold.
4. Weight Clipping: Weight clipping is a method of increasing weights if they surpass a certain threshold.

Explain Like I'm 5 (ELI5)

Clipping is a technique we use in machine learning to prevent the computer from making too many changes at once, similar to placing limits on how quickly it can alter things. This helps ensure that computers learn slowly and avoid making costly errors.