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Carry state

As explained in Deep Learning with R, Third Edition

A carry state is an information stream in an LSTM that transports a representation across sequence timesteps for later modification or use.

A carry state is an information stream that transports a representation across sequence timesteps, where later operations can modify or use it. section 13.3.2

Within an LSTM cell, the carry state:

  • Combines with the input and recurrent connection to influence the next output and next state. section 13.3.2
  • Updates through three transformations associated with the input, forget, and candidate paths. section 13.3.2
  • Uses the forget path to scale existing information and the input and candidate paths to add new information. section 13.3.2

Carry update

The update can be written as c_t+1 = i_t * k_t + c_t * f_t. The weights learn how these operations behave, so their intuitive roles are not fixed. section 13.3.2

Figure 13.8 Going from a SimpleRNN to an LSTM: adding a carry track
figure

Compare the SimpleRNN cell with the added carry track to visualize how LSTM information flow expands across timesteps. section 13.3.2

How Deep Learning with R, Third Edition covers it

How deep it goes
Descends to the LSTM carry equation and transformations, while stopping short of assigning fixed meanings to learned operations.
Examples
Uses an LSTM anatomy figure and pseudocode showing output, gate, and carry-state calculations.
What it assumes
Builds from the SimpleRNN cell and recurrent state before adding the LSTM carry track.
What you can do after
Evaluate how an LSTM transports, forgets, and incorporates information through its carry pathway.
How it connects
Connects carry state with LSTM cells, SimpleRNN cells, recurrent connections, hidden state, and input and forget gates.

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This explainer was generated by Manning's knowledge graph from the text of Deep Learning with R, Third Edition. The section links point to the parts of the book it draws on.