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What is Long Short Term Memory (LSTM) - Complete Guide

18th Sep, 2023
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    What is Long Short Term Memory (LSTM) - Complete Guide

    What is Long Short-Term Memory (LSTM)? This question has been asked lately with the release of several new smartphones and devices that include LSTM technology. While LSTM hasn't quite hit the mainstream yet, it's something you should be familiar with. In this post, we'll take a detailed look at what LSTM is and how it works. We'll also explore some of the benefits of using LSTM and discuss possible applications for this innovative technology. So, if you're curious about LSTM or just want to learn more about it, keep reading!


    What is Long Short Term Memory (LSTM)?

    Long short-term memory (LSTM) is the artificial recurrent neural network (RNN) architecture used in the field of deep learning. Unlike standard RNNs, LSTM has "memory cells" that can remember information for long periods of time. It also has three gates that control the flow of information into and out of the memory cells: the input gate, the forget gate, and the output gate.  

    LSTM networks have been used on a variety of tasks, including speech recognition, language modeling, and machine translation. In recent years, they have also been used for more general sequence learning tasks such as activity recognition and music transcription. 

    Ideology Behind LSTMs and How Does It Work?

    So, as we are now through with the basic question, “what is long short term memory” let us move on to the ideology behind Long short term memory networks. Humans can remember memories from the distant past, as well as recent events, and we can also easily recall sequences of events. LSTMs are designed to mimic this ability, and they have been shown to be successful in a variety of tasks, such as machine translation, image captioning, and even handwriting recognition. Does this bring an easy undertaking to “What is the long-term memory”? 

    But we are now here with the question, how do Long Short-Term Memory networks work? As quoted everywhere in the basic Database Courses, the key difference between LSTMs and other types of neural networks is the way that they deal with information over time. Traditional neural networks process information in a “feedforward” way, meaning that they take in input at one-time step and produce an output at the next time step.  

    LSTMs, on the other hand, can process information in a “recurrent” way, meaning that they can take in input at one-time step and use it to influence their output at future time steps. This recurrent processing is what allows LSTMs to learn from sequences of data. 

    There are four main components to an LSTM network: the forget gate, the input gate, the output gate, and the cell state. The forget gate controls how much information from the previous time step is retained in the current time step. The input gate controls how much new information from the current time step is added to the cell state. The output gate controls how much information from the cell state is used to produce an output at the current time step. And finally, the cell state is a vector that represents the “memory” of the LSTM network; it contains information from both the previous time step and the current time step. 

    Recurrent Neural Networks

    Recurrent neural networks (RNNs) are a type of artificial neural network that is well-suited for processing sequential data such as text, audio, or video. RNNs have a recurrent connection between the hidden neurons in adjacent layers, which allows them to retain information about the previous input while processing the current input.  

    This makes RNNs particularly useful for tasks such as language translation or speech recognition, where understanding the context is essential. A long, short term memory neural network is designed to overcome the vanishing gradient problem, which can occur when training traditional RNNs on long sequences of data. LSTMs have been shown to be effective for a variety of tasks, including machine translation and image captioning. 

    Long Short-Term Memory Networks

    Long Short-Term Memory networks are a type of recurrent neural network designed to model complex, sequential data. Unlike traditional RNNs, which are limited by the vanishing gradient problem, LSTMs can learn long-term dependencies by using a method known as gated recurrent units (GRUs). GRUs contain a "forget" gate, which allows them to selectively forget information from the previous timestep, and an "update" gate, which allows them to control how much information from the current timestep is passed on to the next time step.  

    This makes LSTMs well-suited for tasks such as machine translation, where it is important to be able to remember and interpret information from long sequences. In addition, LSTMs can be trained using a variety of different methods, including backpropagation, through time and reinforcement learning. 

    LSTM vs. RNN

    Long Short-Term Memory neural networks are types of recurrent neural networks (RNN) that are well-suited for modeling sequence data. In contrast to RNNs, which tend to struggle with long-term dependencies, LSTMs can remember information for extended periods of time. This makes them ideal for tasks such as language modeling, where it is important to be able to capture the context of a sentence to predict the next word. LSTMs are also commonly used in machine translation and speech recognition applications. 

    There are a number of advantages that LSTMs have over traditional RNNs.  

    • First, they are much better at handling long-term dependencies. This is due to their ability to remember information for extended periods of time.  
    • Second, LSTMs are much less susceptible to the vanishing gradient problem. This is because they use a different kind of activation function, known as an LSTM cell, which helps to preserve information over long sequences.  
    • Finally, LSTMs are very efficient at modeling complex sequential data. This is because they can learn high-level representations that capture the structure of the data. 

    Despite these advantages, LSTMs do have some drawbacks.  

    • First, they are more complicated than traditional RNNs and require more training data in order to learn effectively.  
    • Second, they are not well-suited for online learning tasks, such as prediction or classification tasks where the input data is not a sequence. Third, LSTMs can be slow to train on large datasets. This is due to the fact that they must learn the parameters of the LSTM cells, which can be computationally intensive.  
    • Finally, LSTMs may not be appropriate for all types of data. For example, they may not work well with highly nonlinear data or data with a lot of noise. 

    What are Bidirectional LSTMs?

    Bidirectional LSTMs are a type of recurrent neural network that is often used for natural language processing tasks. Unlike traditional LSTMs, which read input sequentially from left to right, bidirectional LSTMs are able to read input in both directions, allowing them to capture context from both the past and the future.  

    This makes them well-suited for tasks such as named entity recognition, where it is important to be able to identify entities based on their surrounding context. Bidirectional LSTMs are also sometimes used for machine translation, where they can help to improve the accuracy of the translation by taking into account words that appear later in the sentence. 

    For a comprehensive look into the world of LSTM, it is advisable to get enrolled in a MongoDB Certification course and learn everything you need to know about these neural networks.  

    LSTM Applications

    LSTM has been used to achieve state-of-the-art results in a wide range of tasks such as language modeling, machine translation, image captioning, and more.  

    1. Language Modeling

    One of the most common applications of LSTM is language modeling. Language modeling is the task of assigning a probability to a sequence of words. In order to do this, LSTM must learn the statistical properties of language so that it can predict the next word in a sentence.  

    2. Machine Translation

    Another common application of LSTM is a machine translation. Machine translation is the process of translating one natural language into another. LSTM has been shown to be effective for this task because it can learn the long-term dependencies that are required for accurate translations.  

    3. Handwriting Recognition

    Handwriting recognition is the task of automatically recognizing handwritten text from images or scanned documents. This is a difficult task because handwritten text can vary greatly in terms of style and quality, and there are often multiple ways to write the same word. However, because LSTMs can remember long-term dependencies between strokes, they have been shown to be effective for handwriting recognition tasks.

    4. Image Captioning

    LSTM can also be used for image captioning. Image captioning is the task of generating a textual description of an image. This is a difficult task because it requires understanding both the visual content of an image and the linguistic rules for describing images. However, LSTM works well at image captioning by learning how to interpret images and generate appropriate descriptions.

    5. Image Generation using Attention Models

    Attention models are a type of neural network that can learn to focus on relevant parts of an input when generating an output. This is especially useful for tasks like image generation, where the model needs to focus on different parts of the image at different times. LSTMs can be used together with attention models to generate images from textual descriptions.  

    6. Question Answering

    LSTMs can also be used for question-answering tasks. Given a question and a set of documents, an LSTM can learn to select passages from the documents that are relevant to the question and use them to generate an answer. This task is known as reading comprehension and is an important testbed for artificial intelligence systems.  

    Recently, Google released the SQuAD dataset, which contains 100,000+ questions answered by crowd workers on a set of Wikipedia articles. A number of different neural networks have been proposed for tackling this challenge, and many of them use LSTMs in some way or another. 

    7. Video-to-Text Conversion

    Video-to-text conversion is the task of converting videos into transcripts or summaries in natural language text. This is a difficult task because it requires understanding both the audio and visual components of the video in order to generate accurate text descriptions. LSTMs have been used to develop successful video-to-text conversion systems.  

    8. Polymorphic Music Modeling

    Polyphonic music presents a particular challenge for music generation systems because each note must be generated independently while still sounding harmonious with all the other notes being played simultaneously. One way to tackle this problem is to use an LSTM network trained on polyphonic music data. This approach has been shown to generate convincing polyphonic music samples that sound similar to human performances.

    9. Speech Synthesis

    Speech synthesis systems typically use some form of acoustic modeling in order to generate speech waveforms from text input. Recurrent neural networks are well suited for this task due to their ability to model sequential data such as speech signals effectively. 

    10. Protein Secondary Structure Prediction

    Protein secondary structure prediction is another important application of machine learning in biology. Proteins are often described by their primary structure (the sequence of amino acids) and their secondary structure (the three-dimensional shape).  

    Secondary structure prediction can be viewed as a sequence labeling task, where each residue in the protein sequence is assigned one of three labels (helix, strand, or coil). Long Short-Term Memory networks have been shown to be effective at protein secondary structure prediction, both when used alone and when used in combination with other methods such as support vector machines.

    Limitations of LSTM

    LSTMs are not perfect, however, and there are certain limitations to their abilities. Here, we'll explore some of those limitations and what they mean for the future of artificial intelligence. 

    1. Temporal Dependencies

    One of the biggest limitations of LSTMs is their inability to handle temporal dependencies that are longer than a few steps. This was demonstrated in a paper published by Google Brain researchers in 2016. The researchers found that when they trained an LSTM on a dataset with long-term dependencies (e.g., 100 steps), the network struggled to learn the task and generalize to new examples.

    This limitation arises because LSTMs use a forget gate to control what information is kept in the cell state and what is forgotten. However, this gate can only forget information that is a few steps back; anything further back is forgotten completely. As a result, LSTMs struggle to remember dependencies that are many steps removed from the current input.

    There are two possible ways to address this limitation: either train a larger LSTM with more cells (which requires more data) or use a different type of neural network altogether. Researchers from DeepMind recently proposed a new type of recurrent neural network called the Neural Stack Machine, which they claim can learn temporal dependencies of arbitrary length.

    However, it remains to be seen whether this model will be able to scale to large datasets and complex tasks like machine translation and automatic question answering.

    2. Limited Context Window Size

    Another limitation of LSTMs is their limited context window size. A context window is the set of inputs that the network uses to predict the next output; for instance, in a language model, an input might be a sequence of words while the output is the next word in the sentence. The size of the context window is determined by the number of recurrent units in the LSTM; typically, this number is between 2 and 4.  

    This means that an LSTM can only consider a limited number of inputs when making predictions; anything outside of the context window is ignored completely. This can be problematic for tasks like machine translation, where it's important to consider the entire input sentence (not just the last few words) in order to produce an accurate translation.  

    There are two possible ways to address this limitation as well: either train a larger LSTM with more cells (which requires more data) or use Attention-based models instead, which have been shown to be better at handling long input sequences. However, both of these methods come with their own trade-offs and challenges (e.g., Attention models usually require more training data). In case you feel these limitations are still in your way, then get in touch with the experts of KnowledgeHut’s Database Courses and solve all your problems with their professional expertise.

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    So far, we’ve learned that LSTM is a powerful memory tool that can be used to improve your studying and learning habits. We’ve looked at some of the ways you can use LSTM to its full potential in order to make the most of your memory. Finally, we’ve discussed how you can apply these same techniques to other areas of your life in order to achieve success. Are you ready to start using LSTM?

    Frequently Asked Questions (FAQs)

    1Why is LSTM better than RNN?

    Long short term memory (LSTM) is the artificial recurrent neural network (RNN) architecture used in the field of deep learning. Unlike standard RNNs, LSTM has the ability to learn long-term dependencies. This is because LSTM introduces the concept of cells, which can remember information for lengthy periods of time. In addition, LSTM networks are well-suited to classification and prediction tasks. For these reasons, LSTM is often seen as superior to standard RNNs. 

    2Is LSTM a deep learning model?

    Yes, LSTM is a deep learning model. LSTMs are a type of recurrent neural network that are well-suited for modeling sequential data. In general, deep learning models are able to learn complex patterns in data that are hard to learn using shallower models. LSTMs are particularly powerful because they can learn long-term dependencies in data, making them very effective for tasks such as language modeling and machine translation.

    3Why do we use LSTM?

    We use LSTM because it helps us to better understand and predict the behavior of stock markets. It can also be used to identify patterns in data that may not be immediately obvious. By understanding these patterns, we can make more informed decisions about when to buy or sell stocks. In addition, LSTM can help us to filter out noise from data, making it easier to identify Trends. 

    4What problem does LSTM solve?

    LSTM is a type of recurrent neural network (RNN) that is designed to deal with the vanishing gradient problem. This is a problem that can occur when training RNNs, whereby the gradients become very small over successive iterations, making it difficult for the network to learn from data. LSTM networks are able to overcome this problem by using gates that control the flow of information through the network. As a result, they are better able to preserve information over long periods of time and can be trained on longer sequences of data.


    Abhresh Sugandhi


    Abhresh is specialized as a corporate trainer, He has a decade of experience in technical training blended with virtual webinars and instructor-led session created courses, tutorials, and articles for organizations. He is also the founder of Nikasio.com, which offers multiple services in technical training, project consulting, content development, etc.

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