BESA: Pruning Large Language Models with Blockwise Parameter-Efficient
  Sparsity Allocation
Peng Xu Wenqi Shao Mengzhao Chen Shitao Tang Kaipeng Zhang Peng Gao Fengwei An Yu Qiao Ping Luo
Large language models (LLMs) have demonstrated outstanding performance in
various tasks, such as text summarization, text question-answering, and etc.
While their performance is impressive, the computational footprint due to their
vast number of parameters can be prohibitive. Existing solutions such as
SparseGPT and Wanda attempt to alleviate this issue through weight pruning.
However, their layer-wise approach results in significant perturbation to the
model's output and requires meticulous hyperparameter tuning, such as the
pruning rate, which can adversely affect overall model performance. To address
this, this paper introduces a novel LLM pruning technique dubbed blockwise
parameter-efficient sparsity allocation (BESA) by applying a blockwise
reconstruction loss. In contrast to the typical layer-wise pruning techniques,
BESA is characterized by two distinctive attributes: i) it targets the overall
pruning error with respect to individual transformer blocks, and ii) it
allocates layer-specific sparsity in a differentiable manner, both of which
ensure reduced performance degradation after pruning. Our experiments show that
BESA achieves state-of-the-art performance, efficiently pruning LLMs like
LLaMA1, and LLaMA2 with 7B to 70B parameters on a single A100 GPU in just five
hours. Code is available at
\href{https://github.com/OpenGVLab/LLMPrune-BESA}{here}.