Lighter-Communication Distributed Machine Learning via Sufficient Factor Broadcasting.

Matrix-parametrized models (MPMs) are widely used in machine learning (ML) applications. In large-scale ML problems, the parameter matrix of a MPM can grow at an unexpected rate, resulting in high communication and parameter synchronization costs. To address this issue, we offer two contributions: first, we develop a computation model for a large family of MPMs, which share the following property: the parameter update computed on each data sample is a rank-1 matrix, i.e. the outer product of two "sufficient factors" (SFs). Second, we implement a decentralized, peer-to-peer system, Sufficient Factor Broadcasting (SFB), which broadcasts the SFs among worker machines, and reconstructs the update matrices locally at each worker. SFB takes advantage of small rank-1 matrix updates and efficient partial broadcasting strategies to dramatically improve communication efficiency. We propose a graph optimization based partial broadcasting scheme, which minimizes the delay of information dissemination under the constraint that each machine only communicates with a subset rather than all of machines. Furthermore, we provide theoretical analysis to show that SFB guarantees convergence of algorithms (under full broadcasting) without requiring a centralized synchronization mechanism. Experiments corroborate SFB's efficiency on four MPMs.