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BitNet v2: Native 4-bit Activations with Hadamard Transformation for 1-bit LLMs

Hongyu Wang, Shuming Ma, Furu Wei

2025-04-28

BitNet v2: Native 4-bit Activations with Hadamard Transformation for
  1-bit LLMs

Summary

This paper talks about BitNet v2, a new way to make large language models work using much less memory and computer power by representing information with only 4 bits, thanks to a special mathematical trick called the Hadamard transformation.

What's the problem?

The problem is that big AI language models usually need a lot of memory and energy because they use higher-precision numbers (like 8 bits or more) to process information. When you try to use fewer bits, the model can lose accuracy, especially because some data points (called outliers) can mess things up.

What's the solution?

The researchers used an online Hadamard transformation, which is a fast and efficient way to spread out information and handle those outliers, allowing the model to use just 4 bits for its calculations without losing much performance. This method helps the model stay accurate while using a lot less memory and computational resources.

Why it matters?

This matters because it makes powerful AI models more affordable and energy-efficient, so they can be used on smaller devices or in situations where saving power and memory is important, without sacrificing their abilities.

Abstract

BitNet v2 enables native 4-bit activation quantization for 1-bit Large Language Models by using an online Hadamard transformation to mitigate activation outliers, achieving performance comparable to 8-bit activations with reduced memory and computational costs.