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Reconstruction loss

As explained in Deep Learning with R, Third Edition

A reconstruction loss measures the discrepancy between original data or representations and their model-generated reconstructions.

A reconstruction loss measures how closely a model-generated reconstruction matches the original data or representation. It gives self-supervised models a target without requiring manually labeled examples: reconstruct the missing or encoded information as accurately as possible. section 16.4.2 section 17.1.2

Use reconstruction loss to:

  • Train foundation models to recover data from a partial representation, supporting later specialization for downstream tasks. section 16.4.2
  • Train a variational autoencoder alongside a regularization loss: reconstruction preserves input content, while regularization shapes the latent distribution. section 17.1.2

Reconstructing an image with a VAE

An encoder maps an input image to latent variables, a latent point is sampled, and a decoder produces a reconstructed image. Reconstruction loss pushes that decoded image toward the original; the accompanying regularization loss encourages a well-rounded latent distribution. section 17.1.2

Figure 17.3 An autoencoder: mapping an input x to a compressed representation and then decoding it back as x’
figure

Trace the basic autoencoder path from input x through a compressed representation to reconstructed output x′. section 17.1.2

How Deep Learning with R, Third Edition covers it

How deep it goes
Defines the metric and its training role, but does not specify a particular numerical error formula.
Examples
Uses partial internet-scale data recovery and decoded image reconstruction as concrete examples.
What you can do after
Evaluate/understand how reconstruction objectives support representation learning and VAE image generation.
How it connects
Connects self-supervised learning, foundation models, variational autoencoders, latent spaces, and regularization loss.

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