arXiv:2505.24791cs.LGcs.AI2025-05被引 2

提出选择性雅可比解码,加速离散自回归归一化流推理。

Accelerating Inference of Discrete Autoregressive Normalizing Flows by Selective Jacobi Decoding

  • 通过选择性雅可比迭代实现并行推理,打破严格顺序依赖。
  • 实测最快提速4.7倍,生成质量与原方法相当。
  • 适合需要快速生成的部署场景,如实时生成应用。

离散归一化流是具有解析对数似然计算和端到端训练优势的生成模型,但为保证可逆性和可计算雅可比行列式,其表达能力受限。近期工作引入自回归建模,显著提升表达能力和生成质量,但序列化推理天然限制并行计算,导致生成速度慢,阻碍实际应用。本文首次发现推理中严格顺序依赖并非必需;在序列建模中,部分变量可不严格依赖所有前序变量进行近似。此外,模型在初始层依赖冗余低,后续层冗余更高。基于此,我们提出选择性雅可比解码策略,通过并行迭代优化加速自回归推理。理论分析表明该方法具有超线性收敛率,且所需迭代次数不超过原始序列方法。跨多个数据集的实证评估验证了该加速技术的通用性与有效性,在现代归一化流模型上实现最高4.7倍的推理加速,同时保持生成质量。

原文摘要 · Abstract (English)

Discrete normalizing flows are promising generative models with advantages such as analytical log-likelihood computation and end-to-end training. However, the architectural constraints to ensure invertibility and tractable Jacobian computation limit their expressive power and practical usability. Recent advancements utilize autoregressive modeling, significantly enhancing expressive power and generation quality. Nevertheless, such sequential modeling inherently restricts parallel computation during inference, leading to slow generation that impedes practical deployment. In this paper, we first identify that strict sequential dependency in inference is unnecessary to generate high-quality samples. We observe that sub-variables in sequential modeling can also be approximated without strictly conditioning on all preceding sub-variables. Moreover, the models tend to exhibit low dependency redundancy in the initial layer and higher redundancy in subsequent layers. Leveraging these observations, we propose to selectively use Jacobi decoding strategy that accelerates its autoregressive inference through parallel iterative optimization. Theoretical analyses demonstrate the method's superlinear convergence rate and guarantee that the number of iterations required is no greater than the original sequential approach. Empirical evaluations across multiple datasets validate the generality and effectiveness of our acceleration technique, achieving up to 4.7 times faster inference on modern normalizing flow models while preserving generation quality.

生成模型推理加速自回归归一化流

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