Experimental Exploration of Building Large Language Models with JAX: From Theory to Practice

This open-source experimental project jax-llm-expts systematically explores how to build language models of different scales using the JAX framework, providing researchers with a complete reference from infrastructure to training optimization. The project is not only a code repository but also a technical report on the application potential of JAX in the field of large model training, covering core content such as JAX advantage analysis, architecture implementation, and experimental results.

Research Background

In today's booming LLM era, most developers are familiar with PyTorch/TensorFlow, but JAX has gradually gained attention from researchers due to its functional programming paradigm and high-performance computing capabilities. The jax-llm-expts project was born to explore the possibility of building LLMs of different scales using JAX.

Reasons for Choosing JAX

1. Functional Programming Advantages: Clear and predictable computation graphs reduce debugging difficulty, laying the foundation for automatic differentiation and parallel computing;
2. High-Performance Computing: Optimized via the XLA compiler, code can be compiled into hardware-specific machine code, approaching the performance of handwritten CUDA;
3. Flexible Parallel Strategies: Provides primitives for data, model, and pipeline parallelism with a concise API, facilitating large-scale distributed training.

Multi-scale Model Support

The project supports model experiments from small-scale (rapid verification), medium-scale (close to production) to large-scale (large-scale training exploration), with a layered design adapted to different computing resources, making it easy to compare performance characteristics.

Core Component Analysis

• Model Architecture Module: Implements JAX versions of mainstream architectures such as Transformer, balancing functional correctness and functional features;
• Training Loop Module: Encapsulates standard training processes, using JIT compilation to improve execution efficiency;
• Data Loading Module: Optimizes large-scale text data loading and preprocessing, improving memory and I/O efficiency;
• Evaluation and Inference Module: Provides model evaluation and text generation functions, supporting common metric calculation and interactive generation.

1. Automatic Differentiation and Gradient Calculation: The automatic differentiation system based on function transformation can accurately compute high-order derivatives, suitable for second-order optimization or gradient analysis scenarios;
2. Hardware Irrelevance: Code can seamlessly switch between CPU/GPU/TPU without modifying business logic, reducing cross-platform deployment costs;
3. Reproducibility Guarantee: Pure functional features ensure consistent output for the same input, providing natural support for experimental reproducibility.

The project's experimental design analyzes JAX performance from multiple dimensions: not only focusing on convergence speed but also analyzing compilation time, memory usage, communication overhead, etc. The experimental results reveal the advantages and limitations of JAX in different scenarios, providing technical selection references for developers using JAX in production environments.

JAX is not a replacement for PyTorch but a complement:

• PyTorch has a larger ecosystem and pre-trained resources;
• JAX has unique advantages in research flexibility and performance optimization; Researchers need to understand the differences and choose the appropriate tool according to their needs.

The open-sourcing of jax-llm-expts provides a starting point for the application of JAX in the field of large models, and we look forward to more production-level models appearing after the JAX ecosystem is improved. For developers who want to dive deep into JAX or try non-PyTorch stacks, the project is an ideal entry material, providing runnable code and best practices.

The technology of large language models is developing rapidly, and framework selection is only one dimension. The jax-llm-expts project reminds us: do not limit ourselves to mainstream solutions, but choose tools according to actual needs. This spirit of exploration is an important driving force for technological progress.