arXiv Computer Vision
Aug 27

SHIFT-LLM: Distribution Shift Correction in Depth-Pruned LLMs

SHIFT-LLM is a training‑free post‑pruning correction framework that inserts a Linear Residual Adapter (LRA) at each depth‑pruned site in large language models. Each LRA preserves the original residual identity while adding a lightweight affine correction calibrated via closed‑form least‑squares regression on a small held‑out set, thereby approximating the hidden state that would have been produced by the removed block. Experiments across multiple model families and benchmarks show that SHIFT‑LLM consistently recovers accuracy lost to depth pruning, achieving gains up to +15.7 points on Llama‑3.1‑8B‑Instruct with only a few hundred calibration samples and no gradient computation.

By Ali Bahri, Hang Li, Hongliang Li, Zhitang Chen
arXiv AI
Sep 3

Scalable Kronecker-Fisher Approximation: Efficient Hessian Analysis for Billion-Parameter Language Models Compression

The paper introduces a scalable Kronecker-based approximation that captures cross-layer interactions without storing the full Fisher matrix, making Hessian analysis feasible for billion-parameter language models. It identifies consistent vulnerability patterns, notably that value projection layers are the most sensitive and exhibit strong cross-layer correlations across various model families. Experiments on quantization, sparsification, inter-layer corruption, and fine-tuning show that the approximation correlates strongly with performance degradation and recovery, providing a practical tool for identifying fragile components and guiding compression and optimization strategies.

By Viacheslav Yusupov, Daria Cherniuk, Evgeny Frolov