Communication-Efficient Distributed SVD via Local Power Iterations
This work addresses communication bottlenecks in distributed computing for SVD, which is incremental as it builds on existing methods with a focus on efficiency improvements.
The paper tackles the problem of communication efficiency in distributed truncated singular value decomposition (SVD) by developing the LocalPower algorithm, which reduces the required number of communications by a factor of p to achieve constant accuracy, as demonstrated in experiments.
We study distributed computing of the truncated singular value decomposition problem. We develop an algorithm that we call \texttt{LocalPower} for improving communication efficiency. Specifically, we uniformly partition the dataset among $m$ nodes and alternate between multiple (precisely $p$) local power iterations and one global aggregation. In the aggregation, we propose to weight each local eigenvector matrix with orthogonal Procrustes transformation (OPT). As a practical surrogate of OPT, sign-fixing, which uses a diagonal matrix with $\pm 1$ entries as weights, has better computation complexity and stability in experiments. We theoretically show that under certain assumptions \texttt{LocalPower} lowers the required number of communications by a factor of $p$ to reach a constant accuracy. We also show that the strategy of periodically decaying $p$ helps obtain high-precision solutions. We conduct experiments to demonstrate the effectiveness of \texttt{LocalPower}.