Gradient sparsification is a communication optimisation technique for scaling and accelerating distributed deep neural network (DNN) training. It reduces the increasing communication traffic for gradient aggregation. However, existing sparsifiers have poor scalability because of the high computational cost of gradient selection and/or increase in communication traffic. In particular, an increase in communication traffic is caused by gradient build-up and inappropriate threshold for gradient selection. To address these challenges, we propose a novel gradient sparsification method called MiCRO. In MiCRO, the gradient vector is partitioned, and each partition is assigned to the corresponding worker. Each worker then selects gradients from its partition, and the aggregated gradients are free from gradient build-up. Moreover, MiCRO estimates the accurate threshold to maintain the communication traffic as per user requirement by minimising the compression ratio error. MiCRO enables near-zero cost gradient sparsification by solving existing problems that hinder the scalability and acceleration of distributed DNN training. In our extensive experiments, MiCRO outperformed state-of-the-art sparsifiers with an outstanding convergence rate.

翻译：梯度稀疏化是一种用于扩展和加速分布式深度神经网络（DNN）训练的通信优化技术。它减少了梯度聚合过程中不断增长的通信流量。然而，现有稀疏化方法由于梯度选择的高计算成本和/或通信流量的增加，可扩展性较差。特别是，梯度累积和梯度选择阈值不当会导致通信流量增加。为应对这些挑战，我们提出了一种名为MiCRO的新型梯度稀疏化方法。在MiCRO中，梯度向量被划分，每个分区分配给对应的工作节点。随后，每个工作节点从其分区中选择梯度，聚合后的梯度不存在累积问题。此外，MiCRO通过最小化压缩比误差，估算精确阈值以按用户需求维持通信流量。MiCRO通过解决阻碍分布式DNN训练可扩展性和加速的现有问题，实现了近乎零成本的梯度稀疏化。在广泛的实验中，MiCRO以出色的收敛速度超越了最先进的稀疏化方法。