论文标题
线性时间同态轨道轨道在有限的退化图中计数的二分法定理
A Dichotomy Theorem for Linear Time Homomorphism Orbit Counting in Bounded Degeneracy Graphs
论文作者
论文摘要
在大输入图G中计算模式图H的同态数量是计算机科学中的一个基本问题。该问题在数据库,图算法和网络科学中都有无数的应用。通常,我们不仅需要总数。尤其是在大型网络分析中,我们希望对G的每个顶点V计算V参与的H型的数量。该问题称为同构轨道计数,因为它与其自动形态下的H轨道有关。 考虑到需要快速算法解决此问题,我们会研究何时可能进行近线性时间算法。自然的限制是假设输入图G具有有限的变性,这是现代大型网络中通常观察到的特性。我们可以表征h可以在接近线性的时间内完成同态轨道计数的模式吗? 我们发现解决此问题的二分法定理。对于模式h,令L为同一轨道的任意两个顶点(在H的自动形态下)之间最长的诱导路径的长度。如果L = <5,则可以在界面的退化图中在接近线性的时间内进行H型摩形轨道计数。如果l> 5,则(假设有细粒的复杂性猜想),此问题没有接近线性的时间算法。我们以现有的二分法定理作品为基础,以计算总H-肌形态数量。令人惊讶的是,存在(并且我们表征)模式h可以在接近线性的时间内计算总代态数量,但是相应的轨道计数问题不能在接近线性的时间内完成。
Counting the number of homomorphisms of a pattern graph H in a large input graph G is a fundamental problem in computer science. There are myriad applications of this problem in databases, graph algorithms, and network science. Often, we need more than just the total count. Especially in large network analysis, we wish to compute, for each vertex v of G, the number of H-homomorphisms that v participates in. This problem is referred to as homomorphism orbit counting, as it relates to the orbits of vertices of H under its automorphisms. Given the need for fast algorithms for this problem, we study when near-linear time algorithms are possible. A natural restriction is to assume that the input graph G has bounded degeneracy, a commonly observed property in modern massive networks. Can we characterize the patterns H for which homomorphism orbit counting can be done in near-linear time? We discover a dichotomy theorem that resolves this problem. For pattern H, let l be the length of the longest induced path between any two vertices of the same orbit (under the automorphisms of H). If l =< 5, then H-homomorphism orbit counting can be done in near-linear time for bounded degeneracy graphs. If l > 5, then (assuming fine-grained complexity conjectures) there is no near-linear time algorithm for this problem. We build on existing work on dichotomy theorems for counting the total H-homomorphism count. Somewhat surprisingly, there exist (and we characterize) patterns H for which the total homomorphism count can be computed in near-linear time, but the corresponding orbit counting problem cannot be done in near-linear time.