Efficient GPU Parallelization of Electronic Transport and Nonequilibrium Dynamics from Electron-Phonon Interactions in the Perturbo Code

TL;DR

This paper introduces a GPU-accelerated implementation of the Boltzmann transport equation solver in the Perturbo code, achieving significant speed-ups and scalability for studying electronic transport and dynamics in materials.

Contribution

The paper presents a novel GPU-optimized data structure and algorithm for the collision integral, enabling 40x faster calculations and linear scaling across multiple GPUs in the Perturbo code.

Findings

Achieves 40x speed-up over CPU implementation.

Nearly linear scaling up to 100 GPUs.

Enables large-scale, high-resolution electron transport studies.

Abstract

The Boltzmann transport equation (BTE) with electron-phonon (e-ph) interactions computed from first principles is widely used to study electronic transport and nonequilibrium dynamics in materials. Calculating the e-ph collision integral is the most important step in the BTE, but it remains computationally costly, even with current MPI+OpenMP parallelization. This challenge makes it difficult to study materials with large unit cells and to achieve high resolution in momentum space. Here, we show acceleration of BTE calculations of electronic transport and ultrafast dynamics using graphical processing units (GPUs). We implement a novel data structure and algorithm, optimized for GPU hardware and developed using OpenACC, to process scattering channels and efficiently compute the collision integral. This approach significantly reduces the overhead for data referencing, movement, and synchronization. Relative to the efficient CPU implementation in the open-source package Perturbo (v2.2.0), used as a baseline, this approach achieves a speed-up of 40 times for both transport and nonequilibrium dynamics on GPU hardware, and achieves nearly linear scaling up to 100 GPUs. The novel data structure can be generalized to other electron interactions and scattering processes. We released this GPU implementation in the latest public version (v3.0.0) of Perturbo. The new MPI+OpenMP+GPU parallelization enables sweeping studies of e-ph physics and electron dynamics in conventional and quantum materials, and prepares Perturbo for exascale supercomputing platforms.