arXiv:2603.17917cs.LGcs.CL2026-03被引 1

权重的相对大小比具体数值更重要,可大幅压缩模型而不损失性能。

Only relative ranks matter in weight-clustered large language models

  • 用聚类替换权重值,仅保留16-64个共享值即可保持模型精度。
  • 打乱权重相对顺序会严重降低性能,即使均值方差不变。
  • 保持相对排序的随机化几乎无损,适合模型压缩与鲁棒性研究。

大语言模型包含数十亿参数,但许多权重的具体数值并非必要。我们发现真正重要的是权重之间的相对排名——即某连接是否强于另一连接,而非其精确值。通过将预训练模型的权重矩阵进行聚类(采用K-means),每矩阵仅用16至64个共享值替代,无需微调即可在磁盘上实现显著压缩,且保持良好准确率。对Llama 3.1-8B-Instruct和SmolLM2-135M均验证有效。若仅微调聚类中心,可恢复30%-40%的剩余性能差距,成本极低。进一步实验显示:固定分配关系而随机化聚类中心时,若破坏权重相对排名,模型质量急剧下降(困惑度可上升数个数量级),即便全局统计量如均值、方差保持不变;反之,仅保持排名的随机化在中后层几乎无损。同时,多层同步扰动表明:规模漂移(scale drift)是主要退化机制,但引入仿射校正 w' = aw + b(a > 0)可有效延缓该现象,因该变换同时保留了排序与整体分布。

原文摘要 · Abstract (English)

Large language models (LLMs) contain billions of parameters, yet many exact values are not essential. We show that what matters most is the relative rank of weights-whether one connection is stronger or weaker than another-rather than precise magnitudes. To reduce the number of unique weight values, we apply weight clustering to pretrained models, replacing every weight matrix with K shared values from K-means. For Llama 3.1-8B-Instruct and SmolLM2-135M, reducing each matrix to only 16-64 distinct values preserves strong accuracy without retraining, providing a simple, training-free method to compress LLMs on disk. Optionally fine-tuning only the cluster means (centroids) recovers 30-40 percent of the remaining accuracy gap at minimal cost. We then systematically randomize cluster means while keeping assignments fixed. Scrambling the relative ranks of the clusters degrades quality sharply-perplexity can increase by orders of magnitude-even when global statistics such as mean and variance are preserved. In contrast, rank-preserving randomizations cause almost no loss at mid and late layers. On the other hand, when many layers are perturbed simultaneously, progressive layer-by-layer replacement reveals that scale drift-not rank distortion-is the dominant collapse mechanism; however, an affine correction w' = aw + b with a > 0 (which preserves both rank order and overall weight distribution) can substantially delay this drift. This rank-based perspective offers a new lens on model compression and robustness.

模型压缩权重聚类相对排名鲁棒性

Thank you to arXiv for use of its open access interoperability. PaperDance 不是 arXiv 官方产品;中文卡片由大模型生成,请以原文为准。