How Do Large Language Models Work? LLM AI Demystified

Unpack the complexity of large language models & explore how AI understands language, tackles bias, and transforms industries.

Barney Dixon, Senior Editor - Omdia

May 30, 2024

9 Min Read

The underlying mechanics, training life cycle and challenges behind LLMs offer insight into how they can transform industry

Generative AI’s meteoric rise in public awareness has made large language models (LLM), such as ChatGPT, household names. But how do LLMs work? Knowing the answer to this question and understanding the nuances of large language model development can help unpack their complexity, enabling users – individuals and businesses alike – to understand how Generative AI understands language, tackles bias and transforms industries.

Unveiling the Mechanics of LLM AI

LLMs undergo an intricate journey from training to their application in real-world scenarios and there are sophisticated mechanisms in place to train and evaluate their performance. This includes a vast pre-training phase, a critical fine-tuning process and a rigorous evaluation phase.

Life Cycle of an LLM

LLMs begin their life cycle with a foundational pre-training phase, during which the model is fed a diverse and extensive dataset. This comprises text from books, articles, websites and various other sources. This stage exposes the model to a wide spectrum of language uses, including syntax, semantics and pragmatics.

This gives the LLMs a fundamental understanding of language, which is an integral part of their ability to generate coherent, contextually relevant responses. During this stage, the LLM is subjected to unsupervised learning techniques, where the model attempts to predict the next word in a sentence given the previous words. In doing so, it learns language patterns, grammar, vocabulary and context without needing explicit instructions.

After this phase, the model is put through a fine-tuning process, during which it is calibrated for more specific tasks, such as translation, summarization and question-answering. This includes more supervised learning, where the model is trained on datasets that include both inputs and the desired output. Doing this allows the model to learn the nuances of specific tasks, such as sentiment analysis or document summarization.

The model then undergoes a rigorous performance evaluation testing its output against practical benchmarks to ensure its efficacy. This stage serves to identify areas of improvement and guide further optimization of the model for specific tasks or general language understanding. This ensures the model is reliable, accurate and ready to handle complex language tasks.

The Architectural Blueprint of Intelligence

The architectural and computational foundations of LLMs underpin their operation. These foundations include Google’s Transformer architecture and the self-attention mechanism – the very building blocks of LLMs that allow them to process and generate language.

Transformer Models: Foundations of Modern LLM

The Transformer model, developed by Google in 2017, is a revolutionary deep learning architecture that provides the foundation upon which modern LLMs are built. The Transformer model processes data in parallel, rather than sequentially as its predecessors did. This significantly enhances the model’s learning efficiency and capacity to handle complex language tasks.

Under the Transformer model, text is converted into numerical representations known as “tokens.” Each token is converted into a vector through a lookup from a word embedding table. The tokens are then contextualized at each layer within the scope of the context window, with other unmasked tokens through a concurrent multi-head attention mechanism.

The attention mechanism is the core principle underlying the Transformer model, specifically self-attention. Previous sequence models processed data sequentially but Transformer processes all elements of the sequence simultaneously, enabling it to capture dependencies between words or tokens, regardless of their positions in the input sequence. The self-attention mechanism enables LLMs to evaluate the relevance of each word in a sentence and consider the context and overall meaning of a sentence.

Delving Into Layers, Nodes and Parameters

Layers, nodes and parameters determine the potential depth, breadth and complexity of a large language model in understanding and generating language. Transformers are made of multiple layers. The primary two sub-layers are the self-attention mechanism and a feedforward neural network.

Each layer of the model processes information at a different level of abstraction using inputs from the previous layer. It gradually refines and abstracts information, from recognizing basic syntax to understanding more nuanced semantics. Within each layer are nodes, the basic computational units that perform calculations on the input data.

The model’s parameters are shifted during training to minimize the difference between its predictions and the actual data. These parameters and how many are used are important factors in the model’s learning capacity. Bigger models with more parameters have the potential to learn more complex patterns but will require more data and resources.

Decoding Encoders and Understanding Decoders

LLMs aren’t just a product of their architecture. Encoders, decoders and fine-tuning methods are important processes that allow LLMs to adapt and evolve to meet ever-changing demands.

In language processing, encoders convert input text into intermediate representations that capture the essence of the input. Decoders use these representations, along with previously generated output, to produce a final text sequence.

The encoder/decoder paradigm is essential in translation models – the encoder processes the input language and the decoder generates the translation in the output language. It is also used in various other large language model tasks, such as summarization, content generation and in ensuring outputs are relevant and contextually relevant.

Reinforcement Learning From Human Feedback

Fine-tuning after initial pre-training is essential for optimizing performance in specific tasks. In this process, the model’s parameters are adjusted based on feedback from task-specific benchmarks, with learning reinforcement based on human feedback.

Often this tuning is based on a dataset designed for a specific application. This enables the LLM to adapt generalized knowledge to the specific tasks set for it. Fine-tuning is a critical aspect of benchmarking a large language model and is required to optimize performance across different use cases.

Incorporating human feedback through reinforcement learning is an advanced step in training an LLM. During this process, the model’s outputs are adjusted based on human preferences and gently guided toward more desired behaviors. In conversational AI, reinforcement learning pushes responses toward engaging and respectful answers aligned with moral, ethical and human standards.

Challenges and Limitations: AI’s Achilles' Heel

Despite recent advances, AI technology continues to present significant and sustained challenges and several key limitations. These include, but are not limited to, algorithmic biases, ethical concerns and the sustainability of their ever-increasing computational demands. These issues stem from a combination of technical constraints, characteristics of the training data and the broader societal and ethical context in which the world operates.

Algorithmic Bias and Ethical Concerns

Algorithmic bias remains a significant challenge for LLMs. In many cases, they can inadvertently perpetuate or amplify perceived biases present in their training data. AI systems generally learn to make statistical predictions based on their training data. If the training data contains biases – this can be due to historical inequalities, prejudiced content or non-representative sampling – they can be learned, repeated and amplified by the AI.

One example could be an LLM trained on predominantly English internet text, which then doesn’t perform as expected in dialects or languages not represented in its training data.

Furthermore, language is nuanced and context dependent. LLMs aren’t necessarily able to understand these nuances, which can often lead to misinterpretation or inappropriate responses. These issues are deepened by idiomatic expressions, regional dialects, cultural references and sarcasm, which all can be misconstrued by a model that has no base of reference for underlying social and cultural contexts.

If AI is to become further integrated into decision-making processes, these issues will need to be addressed. The potential for misuse continues to grow. The use of AI also raises concerns about privacy, surveillance, automation, consent, equity and the distribution of its benefits and harms.

Energy Demands and Sustainability

From a resource limitation perspective, the intensity of training and operating LLMs has raised various concerns about their environmental impact. Training LLMs requires significant computational load, with powerful graphics processing units (GPU) and tensor processing units (TPU) running at high capacity for weeks, or sometimes even months. This in turn consumes a large amount of electricity, which contributes to carbon emissions – especially if the energy source is not renewable. Training AI also uses a vast amount of water to cool the server farms carrying out the processing. 

With this also comes the problem of scale. As developers pursue larger and larger models, the energy requirements scale dramatically. Many argue that ever-growing models are unsustainable and there are diminishing returns on performance when compared to the increase in computational and energy costs.

Researchers are exploring avenues that could make AI more energy efficient, as sustainability concerns remain.

Generalization and Overfitting

Large language models excel at tasks similar in scope to their training but their ability to understand new contexts and situations can often be limited. AI models do not have the same level of abstract thinking and world knowledge a human might possess, leading to a lack of understanding or reasoning in completely novel situations.

Overfitting, where a model performs well on their training data, but poorly on a real task, can also occur. This generally happens when models memorize specific training examples, rather than learning general patterns, which reduces their effectiveness in real-world applications.

Black Box Nature

Large language models are often described as having a “black box nature.” This is usually due to the general difficulty in understanding how they arrive at specific outputs. This is particularly prevalent in models based on deep learning. The lack of transparency can be problematic when it comes to sensitive applications, for example, in a medical setting or criminal justice scenario, where understanding the rationale behind a decision can be crucial.

Efforts to make AI more explainable exist and usually revolve around techniques that trace decisions back to individual factors. However, increasing complexity poses significant challenges in this respect and complicates the task of holding AI systems accountable for their decisions.

Security Considerations

AI systems can also be vulnerable to adversarial attacks. Small changes to input data can lead to botched outputs. For LLMs, this could mean altering just a few words and characters that, while imperceptible to human users, could cause the model to make major errors. For example, if a company has a chatbot that interacts with customers, a small, imperceptible change in its input data could result in it sharing customer information with bad actors.

AI systems are also vulnerable at the pre-training, data-feeding stage, where malicious data can be inserted into the training set, causing the model to learn undesirable behaviors. Robust data verification and model testing processes are a must to ensure the reliability of these systems.

LLM Evolution

Large language models are rapidly evolving and developers continue to surprise users with the rapid pace of innovation in artificial intelligence. Early on, generative AI development was commonly open source, which means there is a sea of information available for those engaged in the finer details of LLMs.

This article only scratches the surface of the complexities of LLMs. However, a good understanding of the foundational architectures of LLMs and the nuances of their learning processes will greatly aid users in understanding the how and why of LLMs.

About the Author(s)

Barney Dixon

Senior Editor - Omdia

Barney Dixon is a Senior Editor at Omdia, with expertise in several areas, including artificial intelligence. Barney has a wealth of experience across a number of publications, covering topics from intellectual property law to financial services and politics.

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