Explaining Tokens - the Language and Currency of AI

17/03/2025

Under the hood of every AI application are algorithms that churn through data in their own language, one based on a vocabulary of tokens.

Tokens are tiny units of data that come from breaking down bigger chunks of information. AI models process tokens to learn the relationships between them and unlock capabilities including prediction, generation and reasoning. The faster tokens can be processed, the faster models can learn and respond.

AI factories - a new class of data centers designed to accelerate AI workloads - efficiently crunch through tokens, converting them from the language of AI to the currency of AI, which is intelligence.

With AI factories, enterprises can take advantage of the latest full-stack computing solutions to process more tokens at lower computational cost, creating additional value for customers. In one case, integrating software optimizations and adopting the latest generation NVIDIA GPUs reduced cost per token by 20x compared to unoptimized processes on previous-generation GPUs - delivering 25x more revenue in just four weeks.

By efficiently processing tokens, AI factories are manufacturing intelligence - the most valuable asset in the new industrial revolution powered by AI.

What Is Tokenization? Whether a transformer AI model is processing text, images, audio clips, videos or another modality, it will translate the data into tokens. This process is known as tokenization.

Efficient tokenization helps reduce the amount of computing power required for training and inference. There are numerous tokenization methods - and tokenizers tailored for specific data types and use cases can require a smaller vocabulary, meaning there are fewer tokens to process.

For large language models (LLMs), short words may be represented with a single token, while longer words may be split into two or more tokens.

The word darkness, for example, would be split into two tokens, dark and ness, with each token bearing a numerical representation, such as 217 and 655. The opposite word, brightness, would similarly be split into bright and ness, with corresponding numerical representations of 491 and 655.

In this example, the shared numerical value associated with ness can help the AI model understand that the words may have something in common. In other situations, a tokenizer may assign different numerical representations for the same word depending on its meaning in context.

For example, the word lie could refer to a resting position or to saying something untruthful. During training, the model would learn the distinction between these two meanings and assign them different token numbers.

For visual AI models that process images, video or sensor data, a tokenizer can help map visual inputs like pixels or voxels into a series of discrete tokens.

Models that process audio may turn short clips into spectrograms - visual depictions of sound waves over time that can then be processed as images. Other audio applications may instead focus on capturing the meaning of a sound clip containing speech, and use another kind of tokenizer that captures semantic tokens, which represent language or context data instead of simply acoustic information.

How Are Tokens Used During AI Training? Training an AI model starts with the tokenization of the training dataset.

Based on the size of the training data, the number of tokens can number in the billions or trillions - and, per the pretraining scaling law, the more tokens used for training, the better the quality of the AI model.

As an AI model is pretrained, it's tested by being shown a sample set of tokens and asked to predict the next token. Based on whether or not its prediction is correct, the model updates itself to improve its next guess. This process is repeated until the model learns from its mistakes and reaches a target level of accuracy, known as model convergence.

After pretraining, models are further improved by post-training, where they continue to learn on a subset of tokens relevant to the use case where they'll be deployed. These could be tokens with domain-specific information for an application in law, medicine or business - or tokens that help tailor the model to a specific task, like reasoning, chat or translation. The goal is a model that generates the right tokens to deliver a correct response based on a user's query - a skill better known as inference.

How Are Tokens Used During AI Inference and Reasoning? During inference, an AI receives a prompt - which, depending on the model, may be text, image, audio clip, video, sensor data or even gene sequence - that it translates into a series of tokens. The model processes these input tokens, generates its response as tokens and then translates it to the user's expected format.

Input and output languages can be different, such as in a model that translates English to Japanese, or one that converts text prompts into images.

To understand a complete prompt, AI models must be able to process multiple tokens at once. Many models have a specified limit, referred to as a context window - and different use cases require different context window sizes.

A model that can process a few thousand tokens at once might be able to process a single high-resolution image or a few pages of text. With a context length of tens of thousands of tokens, another model might be able to summarize a whole novel or an hourlong podcast episode. Some models even provide context lengths of a million or more tokens, allowing users to input massive data sources for the AI to analyze.

Reasoning AI models, the latest advancement in LLMs, can tackle more complex queries by treating tokens differently than before. Here, in addition to input and output tokens, the model generates a host of reasoning tokens over minutes or hours as it thinks about how to solve a given problem.

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LINK:	https://blogs.nvidia.com/blog/ai-tokens-explained/...
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