Exploring Forgetting in Large Language Model Pre-Training
Chonghua Liao, Ruobing Xie, Xingwu Sun, Haowen Sun, Zhanhui Kang · 2025
Catastrophic forgetting remains a formidable obstacle to building an omniscient model in large language models (LLMs).Despite the pioneering research on task-level forgetting in LLM fine-tuning, there is scant focus on forgetting during pre-training.We systematically explored the existence and measurement of forgetting in pre-training, questioning traditional metrics such as perplexity (PPL) and introducing new metrics to better detect entity memory retention.Based on our revised assessment of forgetting metrics, we explored low-cost, straightforward methods to mitigate forgetting during the pre-training phase.In addition, we carefully analyzed the learning curves, offering insights into the dynamics of forgetting.Extensive evaluations and analyses on forgetting of pre-training could facilitate future research on LLMs.