Highly Scalable Deep Learning Training System with Mixed-Precision: Training ImageNet in Four Minutes

TL;DR

This paper introduces a highly scalable deep learning training system that leverages mixed-precision techniques and optimized algorithms to train large neural networks on massive GPU clusters in record time, notably training ImageNet in just a few minutes.

Contribution

The paper presents a novel mixed-precision training method, an optimization approach for extremely large mini-batch sizes, and highly optimized all-reduce algorithms for scalable GPU clusters.

Findings

Achieved ImageNet training in 6.6 minutes with 2048 GPUs.

Improved training throughput without accuracy loss using mixed-precision.

Significantly faster all-reduce algorithms outperform existing methods.

Abstract

Synchronized stochastic gradient descent (SGD) optimizers with data parallelism are widely used in training large-scale deep neural networks. Although using larger mini-batch sizes can improve the system scalability by reducing the communication-to-computation ratio, it may hurt the generalization ability of the models. To this end, we build a highly scalable deep learning training system for dense GPU clusters with three main contributions: (1) We propose a mixed-precision training method that significantly improves the training throughput of a single GPU without losing accuracy. (2) We propose an optimization approach for extremely large mini-batch size (up to 64k) that can train CNN models on the ImageNet dataset without losing accuracy. (3) We propose highly optimized all-reduce algorithms that achieve up to 3x and 11x speedup on AlexNet and ResNet-50 respectively than NCCL-based training on a cluster with 1024 Tesla P40 GPUs. On training ResNet-50 with 90 epochs, the state-of-the-art GPU-based system with 1024 Tesla P100 GPUs spent 15 minutes and achieved 74.9\% top-1 test accuracy, and another KNL-based system with 2048 Intel KNLs spent 20 minutes and achieved 75.4\% accuracy. Our training system can achieve 75.8\% top-1 test accuracy in only 6.6 minutes using 2048 Tesla P40 GPUs. When training AlexNet with 95 epochs, our system can achieve 58.7\% top-1 test accuracy within 4 minutes, which also outperforms all other existing systems.