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arXiv 2401.01019cs.DS
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具有绝对误差保证的单源个性化PageRank近似

Approximating Single-Source Personalized PageRank with Absolute Error Guarantees

Zhewei Wei, Ji-Rong Wen, Mingji Yang

AI总结:

针对单源个性化PageRank查询,提出具有绝对误差保证的近似算法,在多种图类型上实现次线性期望运行时间,并改进度归一化误差情形的复杂度。

摘要:

个性化PageRank(PPR)是一种在图中被广泛研究和应用的节点邻近度度量。对于图G=(V,E)上的一对节点s和t,PPR值π(s,t)定义为从s出发的α折扣随机游走终止于t的概率,其中游走在每一步以概率α终止。我们研究经典的单源PPR查询问题,该问题要求从给定源节点s到图中所有节点的PPR近似值。具体而言,我们旨在提供具有绝对误差保证的近似,确保所得的PPR估计值π̂(s,t)满足max_{t∈V}|π̂(s,t)-π(s,t)|≤ε,其中ε为给定的误差界。我们提出了一种算法,以高概率实现这一目标,其期望运行时间为:对于有向图,为Õ(√m/ε),其中m=|E|;对于无向图,为Õ(√d_max/ε),其中d_max是图中的最大节点度;对于幂律图,为Õ(n^{γ-1/2}/ε),其中n=|V|,γ∈(1/2,1)是幂律的程度。这些次线性界改进了现有结果。我们还研究了需要度归一化绝对误差保证的情况,要求max_{t∈V}|π̂(s,t)/d(t)-π(s,t)/d(t)|≤ε_d,其中ε_d为给定的误差界,图是无向的,d(t)是节点t的度。我们给出了一种算法,以高概率提供这种误差保证,实现期望复杂度为Õ(√(∑_{t∈V}π(s,t)/d(t))/ε_d)。这改进了先前已知的O(1/ε_d)复杂度。

英文摘要:

Personalized PageRank (PPR) is an extensively studied and applied node proximity measure in graphs. For a pair of nodes $s$ and $t$ on a graph $G=(V,E)$, the PPR value $π(s,t)$ is defined as the probability that an $α$-discounted random walk from $s$ terminates at $t$, where the walk terminates with probability $α$ at each step. We study the classic Single-Source PPR query, which asks for PPR approximations from a given source node $s$ to all nodes in the graph. Specifically, we aim to provide approximations with absolute error guarantees, ensuring that the resultant PPR estimates $\hatπ(s,t)$ satisfy $\max_{t\in V}\big|\hatπ(s,t)-π(s,t)\big|\le\varepsilon$ for a given error bound $\varepsilon$. We propose an algorithm that achieves this with high probability, with an expected running time of - $\widetilde{O}\big(\sqrt{m}/\varepsilon\big)$ for directed graphs, where $m=|E|$; - $\widetilde{O}\big(\sqrt{d_{\mathrm{max}}}/\varepsilon\big)$ for undirected graphs, where $d_{\mathrm{max}}$ is the maximum node degree in the graph; - $\widetilde{O}\left(n^{γ-1/2}/\varepsilon\right)$ for power-law graphs, where $n=|V|$ and $γ\in\left(\frac{1}{2},1\right)$ is the extent of the power law. These sublinear bounds improve upon existing results. We also study the case when degree-normalized absolute error guarantees are desired, requiring $\max_{t\in V}\big|\hatπ(s,t)/d(t)-π(s,t)/d(t)\big|\le\varepsilon_d$ for a given error bound $\varepsilon_d$, where the graph is undirected and $d(t)$ is the degree of node $t$. We give an algorithm that provides this error guarantee with high probability, achieving an expected complexity of $\widetilde{O}\left(\sqrt{\sum_{t\in V}π(s,t)/d(t)}\big/\varepsilon_d\right)$. This improves over the previously known $O(1/\varepsilon_d)$ complexity.

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