What does the update gate in an LSTM cell do?

The update gate in an LSTM (Long Short-Term Memory) cell plays a crucial role in determining which new information should be added to the cell's internal state. It is responsible for regulating the flow of information into the memory cell by deciding how much of the new input data should be considered relative to the existing memory. This gate computes a value between 0 and 1 for each piece of input data, allowing the LSTM to blend the old memory with the new information.

If the update gate outputs a value close to 1 for a certain input, it indicates that a significant portion of the new data will be added to the state. Conversely, a value close to 0 suggests that little or no new information will update the state. This mechanism is essential for enabling LSTMs to learn and remember long-term dependencies in the data while efficiently managing the information flow. Thus, the update gate effectively serves to update the memory with relevant new information, facilitating the model's ability to make predictions based on past inputs while adapting quickly to new data.