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Momentum

As explained in Sutskever's List

Momentum is an optimization technique that incorporates a running history of parameter updates to smooth and accelerate training.

Momentum carries a running history of parameter updates into later steps. In mini-batch SGD, where each batch gives a noisy estimate of the downhill direction, averaging recent steps can reduce sideways jitter and help progress across shallow plateaus. section 2.5.4

A hiker in fog

A hiker can see only a small patch of a mountain and may misjudge the downhill direction. Momentum acts like inertia: instead of reacting sharply to each new patch, the hiker carries recent steps forward, gliding through plateaus and avoiding some sideways jitter. section 2.5.4

AlexNet used momentum of 0.9 with mini-batch SGD and batches of 128 images. It was one part of a larger set of training choices—including ReLU activations, weight initialization, dropout, and data augmentation—that helped make deep learning work at scale. section 2.5.4 section 2.5.5

How Sutskever's List covers it

How deep it goes
Explains momentum through noisy steps and a hiking analogy, but gives no mathematical update rule.
Examples
Uses a fog-bound hiker to illustrate noisy gradient estimates and momentum's smoothing effect.
What it assumes
Recaps gradients, mini-batch sampling, and first-order descent before explaining momentum.
What you can do after
Apply momentum to smooth noisy mini-batch updates and move through shallow plateaus during neural-network training.
How it connects
Connects momentum to mini-batch SGD, gradients, learning rate, and other neural-network training choices.

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This explainer was generated by Manning's knowledge graph from the text of Sutskever's List. The section links point to the parts of the book it draws on.