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Vanishing gradient problem

As explained in Data Without Labels

The vanishing gradient problem is an optimization difficulty in which gradients become extremely small during learning, hindering the retention of information across many sequence steps.

The vanishing gradient problem occurs when gradients become extremely small as they propagate backward through many layers or sequence steps. Learning then slows, and recurrent networks struggle to retain information from far back in a sequence. section 8.7.1 section 8.9.1

The problem appears in several neural-network settings:

  • Plain recurrent neural networks can lose long-term dependencies because gradients vanish while information moves across time steps. section 8.7.1
  • Deep belief networks can encounter diminishing gradients as errors propagate backward through many layers, complicating fine-tuning. section 8.9.1
  • Long short-term memory networks mitigate the problem with input, forget, and output gates that regulate information flow. section 8.7.1
Figure 8.14 The RNN process. RNNs have internal memory, which allows them to use information from the previous inputs to influence the current input and outputs.
figure

Use the RNN process diagram to trace how hidden-state information passes from previous inputs into current inputs and outputs, clarifying why long sequences challenge information retention. section 8.7.1

How Data Without Labels covers it

How deep it goes
Defines gradient diminution and its training effect, then identifies LSTM gates as mitigation without detailing their implementation.
Examples
Uses chatbot sequence handling, speech recognition, and deep belief network fine-tuning to illustrate the problem’s practical consequences.
What you can do after
Evaluate why plain recurrent networks and deep belief networks lose learning effectiveness, and recognize LSTM gating as a mitigation.
How it connects
Connects recurrent neural networks, long-term dependencies, long short-term memory, gated recurrent units, deep belief networks, and restricted Boltzmann machines.

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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.