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Deep belief network

As explained in Data Without Labels

A deep belief network is a generative neural-network model composed of multiple layers of stochastic latent variables, typically structured as restricted Boltzmann machines.

A deep belief network (DBN) is a generative neural-network model composed of multiple layers of stochastic binary latent variables. Each layer is a restricted Boltzmann machine (RBM): its visible units represent observed data, while its hidden units learn features. section 8.9 section 8.9.1

Train a DBN through two connected phases:

  • Pretrain the RBMs layer by layer without labeled data. The first layer captures lower-level features, while later layers learn increasingly abstract representations. section 8.9.1
  • Use contrastive divergence to approximate each layer’s log-likelihood gradient through Gibbs sampling, adjusting weights to model the input distribution. section 8.9.1
  • Fine-tune the complete network with labeled data and backpropagation, minimizing prediction error for a supervised task such as classification. section 8.9.1

This staged approach can learn complex representations for image or speech recognition and organize unlabeled data. Computational expense, overfitting, vanishing gradients, and intricate fine-tuning can limit performance. section 8.13

Recognition pipeline

Feed unlabeled inputs into successive RBMs to learn increasingly abstract features, then fine-tune the network with labeled examples for classification, image recognition, or speech recognition. section 8.9.1 section 8.13

How Data Without Labels covers it

How deep it goes
Explains RBM layers, contrastive divergence, Gibbs sampling, layer-wise pretraining, and fine-tuning, while noting optimization challenges.
Examples
Applies learned representations to image recognition, speech recognition, and classification.
What it assumes
Assumes neural-network and unsupervised-learning familiarity while defining RBMs, visible units, hidden units, and the training sequence.
What you can do after
Evaluate how layered unsupervised pretraining supports classification and recognition while accounting for computational and optimization risks.
How it connects
Connects restricted Boltzmann machines, contrastive divergence, Gibbs sampling, Boltzmann learning, backpropagation, and supervised learning.

Related concepts

This explainer was generated by Manning's knowledge graph from the text of Data Without Labels. The section links point to the parts of the book it draws on.