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Dropout

As explained in Grokking Machine Learning

A neural-network regularization technique that randomly omits units during training to reduce co-adaptation and overfitting.

Imagine training a team where the same few people always do the work. The others never learn. Dropout prevents this by randomly removing neural-network units during training, giving different units opportunities to update their weights and reducing overfitting. section 10.2

During training, dropout works as a simple repeating procedure:

Dropout in a Keras classifier

A classifier for a two-feature circular dataset uses hidden layers of 128 and 64 ReLU units, with Dropout(.2) between them. The value .2 specifies the dropout probability used in those layers. The model ends with a two-unit softmax output and is trained with categorical cross-entropy and Adam. section 10.3

How Grokking Machine Learning covers it

How deep it goes
Defines random node removal and demonstrates Keras placement, but does not derive dropout mathematically or discuss its inference behavior.
Examples
Uses a circular two-feature classifier and an MNIST digit classifier with dropout layers between dense hidden layers.
What it assumes
Assumes familiarity with neural-network layers and training while explaining dropout within broader discussions of overfitting and backpropagation.
What you can do after
Apply it via Keras by inserting Dropout layers with a chosen probability between neural-network layers.
How it connects
Connects dropout with neural networks, overfitting, regularization, backpropagation, and activation functions.

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