Tag
The author shares lessons from building NeuralDBG, an open-source debugger for PyTorch training loops that detects localized failures like vanishing/exploding gradients by monitoring per-layer gradient norm transitions instead of global loss. Practical code snippets and community questions are included.
A technical deep-dive into common causes of failed pretraining runs in large language models, including causality-breaking issues in expert routing and numerical precision bugs, with examples from Llama 4, Gemini 2 Pro, and GPT-4.