COMQ: A Backpropagation-Free Algorithm for Post-Training Quantization
<|reference_start|>COMQ: A Backpropagation-Free Algorithm for Post-Training Quantization: Post-training quantization (PTQ) has emerged as a practical approach to compress large neural networks, making them highly efficient for deployment. However, effectively reducing these models to their low-bit counterparts without compromising the original accuracy remains a key challenge. In this paper, we propose an innovative PTQ algorithm termed COMQ, which sequentially conducts coordinate-wise minimization of the layer-wise reconstruction errors. We consider the widely used integer quantization, where every quantized weight can be decomposed into a shared floating-point scalar and an integer bit-code. Within a fixed layer, COMQ treats all the scaling factor(s) and bit-codes as the variables of the reconstruction error. Every iteration improves this error along a single coordinate while keeping all other variables constant. COMQ is easy to use and requires no hyper-parameter tuning. It instead involves only dot products and rounding operations. We update these variables in a carefully designed greedy order, significantly enhancing the accuracy. COMQ achieves remarkable results in quantizing 4-bit Vision Transformers, with a negligible loss of less than 1% in Top-1 accuracy. In 4-bit INT quantization of convolutional neural networks, COMQ maintains near-lossless accuracy with a minimal drop of merely 0.3% in Top-1 accuracy.<|reference_end|>
@article{zhang2024comq:,
    title={COMQ: A Backpropagation-Free Algorithm for Post-Training Quantization},
    author={Aozhong Zhang, Zi Yang, Naigang Wang, Yingyong Qi, Jack Xin, Xin Li,
  Penghang Yin},
    journal={arXiv preprint arXiv:2403.07134},
    year={2024},
    archivePrefix={arXiv},
    eprint={2403.07134},
    primaryClass={cs.LG cs.CV}
}