  This paper considers the decentralized composite optimization problem. We
propose a novel decentralized variance-reduced proximal-gradient algorithmic
framework, called PMGT-VR, which is based on a combination of several
techniques including multi-consensus, gradient tracking, and variance
reduction. The proposed framework relies on an imitation of centralized
algorithms and we demonstrate that algorithms under this framework achieve
convergence rates similar to that of their centralized counterparts. We also
describe and analyze two representative algorithms, PMGT-SAGA and PMGT-LSVRG,
and compare them to existing state-of-the-art proximal algorithms. To the best
of our knowledge, PMGT-VR is the first variance-reduction method that can solve
decentralized composite optimization problems. Numerical experiments are
provided to demonstrate the effectiveness of the proposed algorithms.
