Large Language Models and MLPs

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Questions and Answers

Random vectors initialized with angles ranging from 0 to 180 degrees tend to be closer to ______ degrees.

90

The ______ lemma explains that the number of nearly perpendicular vectors that can be packed into a space grows exponentially with the number of dimensions.

Johnson-Lindenstrauss

LLMs process text by breaking it into ______, which are then represented by high-dimensional vectors.

tokens

Large language models might probe at many more ______ than their dimensions by utilizing nearly perpendicular directions.

<p>features</p> Signup and view all the answers

The ______ between vectors and specific directions can indicate the presence of a particular feature.

<p>dot products</p> Signup and view all the answers

Key aspects of transformer training include: a specific cost function used for language models, fine-tuning using ______ with human feedback, and scaling laws.

<p>Reinforcement Learning</p> Signup and view all the answers

In the first step of MLP processing, the input vector is multiplied by a large matrix (W up), where each row represents a ______ for a specific feature.

<p>query</p> Signup and view all the answers

The ______ function converts negative values in the vector to zero, creating activated neurons in the MLP.

<p>ReLU</p> Signup and view all the answers

______ autoencoders are a tool used to extract features even when they are superimposed across neurons.

<p>Sparse</p> Signup and view all the answers

The concept of ______ explains how LLMs store vast amounts of information efficiently by encoding multiple features using slightly non-orthogonal vectors.

<p>superposition</p> Signup and view all the answers

Flashcards

Large Language Model (LLM)

A model that predicts the next word based on stored knowledge.

Multi-layer Perceptrons (MLPs)

Neural networks essential for storing and processing facts in LLMs.

Tokens

Pieces of text processed by LLMs, represented as high-dimensional vectors.

Attention

Mechanism that allows vectors in MLPs to share information.

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Superposition

Concept where multiple features are encoded in slightly non-orthogonal vectors.

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Johnson-Lindenstrauss Lemma

A theorem stating that high-dimensional space can embed points so they remain nearly perpendicular with fewer dimensions.

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Feature Space

The multi-dimensional space in which data features are represented as vectors for models to process.

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Sparse Autoencoders

Neural networks that learn to represent data by extracting key features from input efficiently, often overlapping.

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Transformer Training

A learning approach utilizing backpropagation and techniques like reinforcement learning for natural language processing tasks.

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Study Notes

How Large Language Models Store Facts

  • Large language models (LLMs) correctly predict the next word, demonstrating stored knowledge of individuals and their associated sports.
  • Multi-layer Perceptrons (MLPs) are crucial for storing factual information within LLMs.
  • LLMs process text by breaking it into tokens, represented as high-dimensional vectors.
  • Attention allows vectors to share information, while MLPs store and process this information.
  • Vectors exist in high-dimensional space, with different directions representing various meanings.
  • Dot products between vectors and specific directions reveal the presence of particular features.
  • MLPs encode facts by altering input vectors, such as linking Michael Jordan to basketball.

How MLPs Process Vectors

  • Step 1: Input vector multiplied by a large matrix (W up). Each row represents a feature query (e.g., "first name Michael"). Dot products indicate feature presence. A bias vector (B up) is added.
  • Step 2: The resulting vector passes through a non-linear function (ReLU), converting negative values to zero. Activated neurons (positive values) correspond to the output of ReLU.
  • Step 3: The output vector is multiplied by another matrix (W down), where columns represent features to be added. Activated neurons dictate added columns from W down to the output vector. A bias vector (B down) is added.
  • Step 4: The final output vector is combined with the original input vector, incorporating the learned features. Parallel processing for all input vectors.

Understanding MLPs and Superposition

  • MLPs have numerous parameters, primarily within these blocks.
  • Individual neurons rarely represent a single feature, but rather a combination of overlapping features.
  • Superposition implies multiple features are encoded by slightly non-orthogonal vectors, enabling efficient information storage in high-dimensional spaces.

Random Vectors and the Johnson-Lindenstrauss Lemma

  • Random vectors, initialized with angles from 0 to 180 degrees, tend towards 90 degrees.
  • Optimization processes can make vectors more perpendicular.
  • The Johnson-Lindenstrauss lemma suggests exponentially increasing nearly perpendicular vectors in higher dimensions.
  • This is significant for LLMs, which benefit from associating independent ideas with nearly perpendicular directions.

Large Language Models and Feature Space

  • LLMs potentially store more ideas than their dimensions due to the exponential increase of nearly perpendicular vectors.
  • This may explain the model performance scaling with size.
  • A space with ten times more dimensions can store more than ten times the independent ideas.
  • This principle applies to the embedding space and MLP neuron vectors.

Superposition and Feature Extraction

  • LLMs might analyze far more features than their dimensions using nearly perpendicular directions.
  • Individual features are not represented by single neurons, but rather combinations of neurons (superposition).
  • Sparse autoencoders are tools to extract features even when superimposed.

Transformer Training

  • Transformer training heavily relies on backpropagation.
  • Key training aspects include the specific cost function used for language models, fine-tuning with RL and human feedback, and scaling laws.

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