introduction to recurrent neural networks (rnn), long short-term memory (lstm) wenjie pei

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Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

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Page 1: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Introduction to Recurrent neural networks (RNN), Long short-

term memory (LSTM)

Wenjie Pei

Page 2: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Artificial Neural Networks

• Feedforward neural networks– ANNs without cycle connections between nodes

• (Feedback) Recurrent neural networks– ANNs with cycle connections between nodes

Page 3: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Feedforward Neural Networks

• Multilayer perceptron (MLP)

Universal function approximation theory:Sufficient nonlinear hidden units approximate any continuous mapping function

Drawback:Output depends only on the current inputNo temporal information dependencies

Page 4: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Recurrent Neural Networks

Advantage: Memory of previous inputsIncorporate contextual information

Feedback from hidden unit activation of last time step to current time step

Universal approximation theory:An RNN with sufficient hidden unitsAny measurable sequence-to-sequence mappingor dynamic system

Page 5: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Recurrent Neural Networks

• Bidirectional RNNs

Page 6: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Recurrent Neural Networks

• Vanishing gradient problem

Sensitivity decay exponentially over the time

Page 7: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Long Short-Term Memory (LSTM)Input gate [0, 1]: How much information from input could go into the cell

Forget gate [0, 1]: How much information from last time step could enter the cell

Output gate [0, 1]: How much information to output

Page 8: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Long Short-Term Memory

• Advantage: long-period time memory

Page 9: Introduction to Recurrent neural networks (RNN), Long short-term memory (LSTM) Wenjie Pei

Applications

• Applications to sequence labeling problems:– Handwritten character recognition– Speech recognition– Protein secondary structure prediction– …

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