Development of an Equation-based Parallelization Method for Multiphase Particle-in-Cell Simulations

TL;DR

This paper introduces an equation-based parallelization method for multiphase particle-in-cell simulations, leveraging GPU intra-node interconnects to significantly accelerate computations and reduce energy consumption.

Contribution

The authors developed MFiX-AI, a GPU-based implementation using equation decomposition, achieving near-linear speedup and energy savings over traditional CPU-based methods.

Findings

Performance of 4 NVIDIA A100 GPUs is comparable to 1000 CPU cores.

Energy savings of up to 90% on single GPU nodes.

Potential for integration with AI/ML models for further acceleration.

Abstract

Manufacturers have been developing new graphics processing unit (GPU) nodes with large capacity, high bandwidth memory and very high bandwidth intra-node interconnects. This enables moving large amounts of data between GPUs on the same node at low cost. However, small packet bandwidths and latencies have not decreased which makes global dot products expensive. These characteristics favor a new kind of problem decomposition called "equation decomposition" rather than traditional domain decomposition. In this approach, each GPU is assigned one equation set to solve in parallel so that the frequent and expensive dot product synchronization points in traditional distributed linear solvers are eliminated. In exchange, the method involves infrequent movement of state variables over the high bandwidth, intra-node interconnects. To test this theory, our flagship code Multiphase Flow with Interphase eXchanges (MFiX) was ported to TensorFlow. This new product is known as MFiX-AI and can produce near identical results to the original version of MFiX with significant acceleration in multiphase particle-in-cell (MP-PIC) simulations. The performance of a single node with 4 NVIDIA A100s connected over NVLINK 2.0 was shown to be competitive to 1000 CPU cores (25 nodes) on the JOULE 2.0 supercomputer, leading to an energy savings of up to 90%. This is a substantial performance benefit for small- to intermediate-sized problems. This benefit is expected to grow as GPU nodes become more powerful. Further, MFiX-AI is poised to accept native artificial intelligence/machine learning models for further acceleration and development.