AI/ML, Cloud Computing, Machine Learning

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Significant Advancement in Deep Learning : Long Short-Term Memory (LSTM)

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Long-term dependencies can be resolved using LSTM, a special type of recurrent neural network.

Let’s see how an LSTM network is structured and operates.


“LSTM” refers to long short-term memory networks employed in deep learning. It is a recurrent neural network (RNNs) capable of learning long-term relationships, particularly in sequence prediction tasks.

It can solve the RNN’s vanishing gradient issue. Persistent memory is implemented using a recurrent neural network, or RNN.

Imagine that when reading a book, you know what happened in the previous chapter or remember the prior scene while watching a film. Like how RNNs operate, they employ stored information to process new input. Due to their inability to remember long-term dependencies, RNN have this drawback. Long-term dependency issues are specifically avoided with LSTMs.

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Working of LSTM

An LSTM is a recurrent neural network that performs numerous math operations to improve memory rather than just passing its results into the following network component.


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The first part specifies whether or not the details from the previous timestamp should be recalled. The second section’s input to this cell is utilized by the cell to try and learn new information. Finally, the cell sends the updated data from the third section’s current timestamp to the succeeding timestamp.

Forget gate, Input gate, and Output gate are the three “gates” of an

Similar to a standard RNN, an LSTM has a hidden state, with H(t-1) denoting the hidden state of the prior timestamp and H(t) denoting the hidden state of the present timestamp. The timestamps C(t-1) and C(t), which stand for the past and current timestamps, respectively, are also used to indicate the cell state of LSTMs. The long-term memory in this situation is the cell state, while the short-term memory is the hidden state.


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LSTM Gates

  1. Forget Gate: The forget gate determines what information must be remembered and what information can be lost. The sigmoid function receives data from the current input X(t) and the hidden state h(t-1). The range of Sigmoid’s output values is 0 to 1. It determines whether the needed fraction of the preceding output. The cell will eventually multiply points one by one using this f(t) value.


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2. Input Gate: The input gate updates the cell status by doing the following –

  • The second sigmoid function initially provides the current state X(t) and the previously hidden state h(t-1). The values are changed between 0 (important) and 1(not-important).
  • The tanh function will then obtain identical data from the hidden state and current state. To regulate the network, the tanh operator will build a vector (C~(t)) containing every possible value between -1 and 1. The output values generated by the activation functions are ready for multiplication point-by-point.


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3. Cell State: The network has enough data from the input and forget gates. The decision-making process and the data storage from the new state in the cell state come next. With the forget vector f(t), the prior cell state C(t-1) is multiplied. Values in the cell state will be removed if the result is 0. The network then updates the cell state by performing point-by-point addition on the input vector i(t) output value, giving the network a new cell state C(t).


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4. Output Gate: The output gate chooses the next concealed state’s value. This state provides details about prior inputs. It turns out that the long-term memory (C(t)) and the present output influence the concealed state. Activate SoftMax on hidden state H(t) if you need to get the output of the current timestamp.


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LSTM Applications

The following areas are where LSTM networks are applied effectively:

  • Language modeling
  • Machine translation
  • Handwriting recognition
  • Image captioning
  • Image generation using attention models
  • Question answering
  • Video-to-text conversion
  • Polymorphic music modeling
  • Speech synthesis
  • Protein secondary structure prediction

LSTM neural networks can solve many intractable tasks by earlier learning algorithms like RNNs. Using LSTM, long-term temporal dependencies may be efficiently captured without facing many optimization challenges. This is applied to solve complex issues.


RNNs can achieve anything, but LSTM networks can do it far more skillfully, enhancing them over RNNs. LSTMs deliver superior outcomes and are undoubtedly a significant advancement in deep learning, despite how daunting they can initially seem. You can anticipate getting more precise predictions and a better understanding of the options available as more of these technologies emerge.

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Drop a query if you have any questions regarding LSTM and I will get back to you quickly.

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1. What is the LSTM model used for?

ANS: – It is used for time-series data processing, prediction, and classification. LSTM has feedback connections, unlike conventional feed-forward neural networks. It can handle single data points (like photos) and complete data streams (such as speech or video). 

2. What is the difference between LSTM and RNN?

ANS: – The recurrent layer of RNNs contains feedback loops. This allows them to keep information in ‘memory’ over time. However, training typical RNNs to address issues that involve learning long-term temporal dependencies can be difficult. LSTM networks are a form of RNN that employs special units in addition to normal units. A ‘memory cell’ in LSTM units may store information for long periods. This memory cell enables them to learn longer-term dependence. 

3. Why is it called LSTM?

ANS: – The unit is called a long short-term memory block because the program uses a structure founded on short-term memory processes to create longer-term memory. These systems are often used, for example, in natural language processing. 

4. Why is LSTM used for prediction?

ANS: – The Long Short-Term Memory (LSTM) recurrent neural network is one form of recurrent neural network used to learn order dependence in sequence prediction issues. Because of its ability to store past data, LSTM is extremely beneficial in predicting stock prices.


Aritra Das works as a Research Associate at CloudThat. He is highly skilled in the backend and has good practical knowledge of various skills like Python, Java, Azure Services, and AWS Services. Aritra is trying to improve his technical skills and his passion for learning more about his existing skills and is also passionate about AI and Machine Learning. Aritra is very interested in sharing his knowledge with others to improve their skills.



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