arXiv:2410.15020cs.LG2024-10NeurIPS被引 3

提出新框架提升局部迭代算法效率,实测速度最高快100倍。

Iterative Methods via Locally Evolving Set Process

  • 用局部演化集过程定义算法局部性,统一分析多种迭代方法。
  • 证明APPR新运行时间上界为$ ilde{O}(ar{vol}(S_t)/(αar{γ}_t))$,更贴近实际表现。
  • 在残差下降几何均值为$Θ( oot\of{α})$时,局部切比雪夫法提速近100倍。

给定阻尼因子 $α$ 和精度容忍度 $ε$, extcite{andersen2006local} 提出近似个性化 PageRank(APPR),是计算 PPR 向量的主流局部方法,其运行时间上界为 $Θ(1/(αε))$,与图规模无关。近期 extcite{fountoulakis2022open} 提出能否用 $ ilde{O}(1/( oot\of{α}ε))$ 次操作实现更快的局部算法。本文注意到 APPR 是高斯-赛德尔法的局部变体,探讨标准迭代求解器是否可有效局部化。提出“局部演化集过程”作为新框架刻画算法局部性,并证明多种标准求解器均可有效局部化。设 $ar{vol}(S_t)$ 与 $ar{γ}_t$ 为活跃节点集 $S_t$ 在过程中体积与残差比的运行平均值,我们证明 $ar{vol}(S_t)/ar{γ}_t \leq 1/ε$,并推导出 APPR 的新运行时间上界 $ ilde{O}(ar{vol}(S_t)/(αar{γ}_t))$,与实际性能一致。当残差下降的几何均值为 $Θ(\sqrt{α})$ 时,存在 $c \in (0,2)$ 使得局部切比雪夫法运行时间为 $ ilde{O}(ar{vol}(S_t)/(\ oot\of{α}(2−c)))$,无需单调性假设。数值实验验证该框架有效性,在真实图上相比标准求解器最高提速百倍。

原文摘要 · Abstract (English)

Given the damping factor $α$ and precision tolerance $ε$, \citet{andersen2006local} introduced Approximate Personalized PageRank (APPR), the \textit{de facto local method} for approximating the PPR vector, with runtime bounded by $Θ(1/(αε))$ independent of the graph size. Recently, \citet{fountoulakis2022open} asked whether faster local algorithms could be developed using $\tilde{O}(1/(\sqrtαε))$ operations. By noticing that APPR is a local variant of Gauss-Seidel, this paper explores the question of \textit{whether standard iterative solvers can be effectively localized}. We propose to use the \textit{locally evolving set process}, a novel framework to characterize the algorithm locality, and demonstrate that many standard solvers can be effectively localized. Let $\overline{\operatorname{vol}}{ (S_t)}$ and $\overlineγ_{t}$ be the running average of volume and the residual ratio of active nodes $\textstyle S_{t}$ during the process. We show $\overline{\operatorname{vol}}{ (S_t)}/\overlineγ_{t} \leq 1/ε$ and prove APPR admits a new runtime bound $\tilde{O}(\overline{\operatorname{vol}}(S_t)/(α\overlineγ_{t}))$ mirroring the actual performance. Furthermore, when the geometric mean of residual reduction is $Θ(\sqrtα)$, then there exists $c \in (0,2)$ such that the local Chebyshev method has runtime $\tilde{O}(\overline{\operatorname{vol}}(S_{t})/(\sqrtα(2-c)))$ without the monotonicity assumption. Numerical results confirm the efficiency of this novel framework and show up to a hundredfold speedup over corresponding standard solvers on real-world graphs.

图算法迭代求解局部化

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