Improving medium-grain partitioning for scalable sparse tensor decomposition

Tensor decomposition is widely used in the analysis of multi-dimensional data. The canonical polyadic decomposition (CPD) is one of the most popular decomposition methods and commonly found by the CPD-ALS algorithm. High computational and memory costs of CPD-ALS necessitate the use of a distributed-memory-parallel algorithm for efficiency. The medium-grain CPD-ALS algorithm, which adopts multi-dimensional cartesian tensor partitioning, is one of the most successful distributed CPD-ALS algorithms for sparse tensors. This is because cartesian partitioning imposes nice upper bounds on communication overheads. However, this model does not utilize the sparsity pattern of the tensor to reduce the total communication volume. The objective of this work is to fill this literature gap. We propose a novel hypergraph-partitioning model, CartHP, whose partitioning objective correctly encapsulates the minimization of total communication volume of multi-dimensional cartesian tensor partitioning. Experiments on twelve real-world tensors using up to 1024 processors validate the effectiveness of the proposed CartHP model. Compared to the baseline medium-grain model, CartHP achieves average reductions of 52, 43 and 24 percent in total communication volume, communication time and overall runtime of CPD-ALS, respectively.