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Unsupervised learning

As explained in Inside Deep Learning: Math, Algorithms, Models

A learning setting in which models are trained without human-provided labels, often by exploiting structure in the data.

Unsupervised learning trains models without human-provided labels by exploiting structure in the input data. Self-supervision creates implicit labels from the input, allowing familiar regression or classification losses to drive learning. section 7.0

Common self-supervised tasks include:

  • Inpainting: reconstruct an obscured portion of an image. section 7.0
  • Image sorting: restore the correct order of shuffled image pieces. section 7.0
  • Autoencoding: reconstruct the original input from the input itself. section 7.0

Autoencoding digits

A larger PyTorch autoencoder expands the encoded representation, reconstructs 28×28 digit images, and trains with mean squared error. Better visual reconstruction does not necessarily prove that the representation is useful. section 7.3

Figure 7.1 Three different types of self-supervised problems: inpainting, image sorting, and autoencoding. In each case, we do not need to know what the image is of because the network will try to predict the original image no matter what. In the first case (red), we randomly block out a portion of the image and ask the network to fill in the missing piece. In the second case, we break the image into pieces, shuffle them, and ask the network to put them back in the correct order. In the last case, we simply ask the network to predict the original image from the original image.

Compare inpainting, image sorting, and autoencoding as three ways to generate targets directly from images. section 7.0

How Inside Deep Learning: Math, Algorithms, Models covers it

How deep it goes
Defines implicit labels and demonstrates reconstruction, but leaves the usefulness of learned representations difficult to evaluate.
Examples
Uses image inpainting, shuffled-image sorting, autoencoding, and reconstructed handwritten digits as concrete examples.
What it assumes
Assumes familiarity with regression or classification losses while motivating label-free learning from zero.
What you can do after
Build an autoencoder that reconstructs inputs using PyTorch modules and mean squared error.
How it connects
Connects self-supervision with autoencoding, regression, classification, reconstruction, and learned representations.

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This explainer was generated by Manning's knowledge graph from the text of Inside Deep Learning: Math, Algorithms, Models. The section links point to the parts of the book it draws on.