PipeDAP: An Efficient Communication Framework for Scheduling Decoupled All-Reduce Primitives in Distributed DNN Training

Communication scheduling effectively improves the scalability of distributed deep learning by overlapping computation and communication tasks during training. However, existing communication scheduling frameworks based on tensor partitioning suffer from two fundamental issues: (1) partitioning schemes at the data volume level introduce extensive startup overheads leading to higher energy consumption, and (2) partitioning schemes at the communication primitive level do not provide optimal scheduling resulting in longer training time. In this paper, we propose an efficient communication mechanism, namely PipeDAP, which schedules decoupled all-reduce operations in a near-optimal order to minimize the time and energy consumption of training DNN models. We build the mathematical model for PipeDAP and derive the near-optimal scheduling order of the reduce-scatter and all-gather operations. Meanwhile, we leverage simultaneous communication of reduce-scatter and all-gather operations to further reduce the startup overheads. We implement the PipeDAP architecture on PyTorch framework, and apply it for distributed training of benchmark DNN models. Experimental results on two GPU clusters demonstrate that PipeDAP achieves up to 1.82x speedup and saves up to 45.4% of energy consumption compared to the state-of-the-art communication scheduling frameworks. PipeDAP's code is available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://github.com/ZJU-CNLAB/PipeDAP</uri>.