论文标题

低频带宽度模型中的稀疏矩阵乘法

Sparse Matrix Multiplication in the Low-Bandwidth Model

论文作者

Gupta, Chetan, Hirvonen, Juho, Korhonen, Janne H., Studený, Jan, Suomela, Jukka

论文摘要

我们在低带宽模型中研究矩阵乘法:有$ n $计算机,我们需要计算两个$ n \ times n $矩阵的产品。最初,计算机$ i $知道每个输入矩阵的行$ i $。在一次通信中,每台计算机可以发送并接收一个$ O(\ log n)$ - 位消息。最终,计算机$ i $必须输出产品矩阵的行$ i $。 我们试图在均匀稀疏的情况下理解此问题的复杂性:每个输入矩阵的每一行和列最多都有$ d $ non-deneros,在产品矩阵中,我们只需要知道每个行或列中最多$ d $元素的值。这正是我们拥有的设置,例如,当我们将矩阵乘法应用于最高度$ d $的三角检测时。我们专注于支持的设置:矩阵的结构已提前已知;仅非零元素的数值未知。 有一种微不足道的算法可以解决$ O(d^2)$ roughs中的问题,但是对于大$ D $,已知存在更好的算法;在适度密集的机制中,问题可以在$ o(dn^{1/3})$回合中解决,对于非常大的$ d $,主要解决方案是使用$ o(n^{1.158})的快速矩阵乘法算法(n^{1.158})$ communication $ communication nounds(用于矩阵乘数乘坐磁场和支持乘以乘以乘以乘以乘以乘以乘以乘以乘以乘以乘以。 在这项工作中,我们表明,对于$ d $的所有值,有可能克服二次障碍:我们提出了一种算法,该算法在$ o(d^{1.907})$(d^{1.907})$ rounds中解决了该域的圆形和圆环,以支持快速矩阵乘法和$ o(d^{1.927})$ n $ $ n $。

We study matrix multiplication in the low-bandwidth model: There are $n$ computers, and we need to compute the product of two $n \times n$ matrices. Initially computer $i$ knows row $i$ of each input matrix. In one communication round each computer can send and receive one $O(\log n)$-bit message. Eventually computer $i$ has to output row $i$ of the product matrix. We seek to understand the complexity of this problem in the uniformly sparse case: each row and column of each input matrix has at most $d$ non-zeros and in the product matrix we only need to know the values of at most $d$ elements in each row or column. This is exactly the setting that we have, e.g., when we apply matrix multiplication for triangle detection in graphs of maximum degree $d$. We focus on the supported setting: the structure of the matrices is known in advance; only the numerical values of nonzero elements are unknown. There is a trivial algorithm that solves the problem in $O(d^2)$ rounds, but for a large $d$, better algorithms are known to exist; in the moderately dense regime the problem can be solved in $O(dn^{1/3})$ communication rounds, and for very large $d$, the dominant solution is the fast matrix multiplication algorithm using $O(n^{1.158})$ communication rounds (for matrix multiplication over fields and rings supporting fast matrix multiplication). In this work we show that it is possible to overcome quadratic barrier for all values of $d$: we present an algorithm that solves the problem in $O(d^{1.907})$ rounds for fields and rings supporting fast matrix multiplication and $O(d^{1.927})$ rounds for semirings, independent of $n$.

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