EP-SVD-LLM: Efficient Post-Training Compression of Large Language Models via Error Propagation Compensation

EP-SVD-LLM is an improved post-training compression method for large language models. Based on SVD-LLM, it introduces an error propagation compensation mechanism. By tracking and actively correcting inter-layer accumulated errors, it achieves higher compression rates while maintaining model performance, solving the error accumulation problem of traditional layer-independent compression and providing a new tool for efficient deployment of large language models.

Modern large language models have huge parameter scales (e.g., 70B parameters in FP16 require 140GB of memory), leading to high deployment costs that restrict their widespread application. Post-training compression techniques reduce computational complexity through mathematical transformations. The SVD method based on low-rank decomposition has solid theoretical foundations, but traditional layer-independent compression has an error accumulation problem—performance degradation in deep networks is far beyond expectations, limiting the improvement of compression rates.

SVD-LLM (proposed in 2024) applies truncation-aware data whitening technology to LLM compression. It analyzes the Hessian matrix of layer outputs to find the compression direction with minimal impact, but the computational overhead of full-precision activation is high. SC-SVD-LLM is improved to sequential compression, using activation outputs from previous compressed layers, which is closer to the inference scenario, but it still does not solve the error accumulation problem.

EP-SVD-LLM introduces an error propagation compensation mechanism based on SC-SVD-LLM. The steps are: 1. Track accumulated activation errors (delta = X_fp - X_hat); 2. Calculate the correction term (correction = W * delta * X_hat^T * H_hat^{-1}); 3. Perform SVD compression after applying the correction term (W* = W + alpha * correction; alpha=0.5 works well). It is implemented using PyTorch, supports Hugging Face format and SVD-specific format, and provides evaluation and fine-tuning scripts.

EP-SVD-LLM was verified on the TinyLlama model, comparing the performance of SVD-LLM, SC-SVD-LLM, and EP-SVD-LLM under different compression rates (0.2-0.8). At medium to high compression rates, the compensation mechanism of EP-SVD-LLM effectively suppresses performance degradation. The project provides reproducible tutorial scripts, allowing users to quickly complete the compression, evaluation, and fine-tuning processes.

The significance of EP-SVD-LLM lies in proposing a systematic error management approach, turning error propagation from a side effect into an actively compensable signal. Application scenarios include: edge device deployment (running with smaller memory), multi-tenant cloud services (reducing resource usage and improving throughput), and model iterative development (quickly generating model versions of different scales).

EP-SVD-LLM is complementary to quantization (preserving floating-point stability), knowledge distillation (no need for teacher model soft labels), and pruning (more efficient structured sparsity). Future directions: combining with quantization technology, extending to other components of Transformers, and adaptive alpha scheduling strategies.

EP-SVD-LLM is an important progress in the field of post-training compression. It improves performance through error propagation compensation, and its open-source implementation is of high quality (complete documentation, reproducible scripts, flexible interfaces). For researchers and engineers, it is not only a practical tool but also a case for understanding inter-layer error transmission, reminding us to pay attention to system-level interaction effects.