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Momentum

As explained in Machine Learning Algorithms in Depth

Momentum is an optimization technique that incorporates an exponentially weighted moving average of past gradients into parameter updates.

Momentum is an optimization technique that accumulates an exponentially decaying moving average of past gradients. Updates continue in directions supported by recent gradients, so their size reflects gradient magnitude and alignment. section 10.4

Momentum is characterized by these practical points:

  • Use the momentum parameter α to control the moving average; common values are 0.5 and 0.9. section 10.4
  • Interpret aligned gradients as reinforcing movement, while the resulting step size depends on the magnitude and alignment of the gradient sequence. section 10.4
  • Distinguish Nesterov momentum by evaluating the gradient after applying the current velocity, which adds a correction factor. section 10.4

Optimizer comparison

Compare momentum with stochastic gradient descent, Nesterov momentum, AdaGrad, RMSProp, and Adam when training a LeNet model on CIFAR-100, using cross-entropy loss and validation accuracy. section 10.4

How Machine Learning Algorithms in Depth covers it

How deep it goes
Explains exponential averaging, gradient alignment, parameter choice, and Nesterov’s evaluation difference, but does not provide a full derivation.
Examples
Compares optimizers through LeNet training on CIFAR-100 using cross-entropy loss and validation accuracy.
What it assumes
Assumes familiarity with gradients, parameter updates, learning rates, and neural-network optimization.
What you can do after
Evaluate momentum alongside alternative optimizers using training loss and validation accuracy.
How it connects
Connects momentum with learning rate, stochastic gradient descent, Nesterov momentum, AdaGrad, RMSProp, and Adam.

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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Machine Learning Algorithms in Depth. The section links point to the parts of the book it draws on.