IntSGD: Adaptive Floatless Compression of Stochastic Gradients

Konstantin Mishchenko, Bokun Wang, Dmitry Kovalev, Peter Richtárik

Keywords: optimization, distributed optimization, compression, theory, parallel training, switchML

Abstract: We propose a family of adaptive integer compression operators for distributed Stochastic Gradient Descent (SGD) that do not communicate a single float. This is achieved by multiplying floating-point vectors with a number known to every device and then rounding to integers. In contrast to the prior work on integer compression for SwitchML by (Sapio et al., 2021), our IntSGD method is provably convergent and computationally cheaper as it estimates the scaling of vectors adaptively. Our theory shows that the iteration complexity of IntSGD matches that of SGD up to constant factors for both convex and non-convex, smooth and non-smooth functions, with and without overparameterization. Moreover, our algorithm can also be tailored for the popular all-reduce primitive and shows promising empirical performance.

One-sentence Summary: We propose the provably convergent and computationally cheap IntSGD algorithm for efficient distributed machine learning.