Theoretical Analysis and Optimization of Peak Memory Usage in PyPWDFT for Heterogeneous GPU High-Performance...

Heterogeneous high-performance computing is increasingly important for large-scale Kohn-Sham density functional theory (DFT) calculations. However, although GPU device memory provides high bandwidth, its limited capacity makes peak memory usage a critical factor that determines the maximum accessible system size. In this work, we analyze and optimize the peak memory usage of PyPWDFT, a Python native plane-wave DFT code, for heterogeneous GPU computing. The main computational stages of plane-wave DFT calculations are systematically examined to identify the dominant contributors to peak memory usage and to derive theoretical estimates of their memory requirements. Guided by this analysis, several targeted optimization strategies are introduced, including the explicit release of the CuPy memory pool, decomposition of vectorized operations, preservation of array memory contiguity, broader use of in-place operations, and additional computations when they can substantially reduce memory usage. The measured peak memory usage agrees closely with the theoretical analysis, demonstrating that with targeted memory optimization, a native Python implementation can achieve memory efficiency comparable to that of compiled-language implementations and enable DFT calculations for a 1536-atom silicon system on a single NVIDIA H200 GPU. Additional memory and performance benchmarks on A100, A800, H100, and H200 GPUs further demonstrate the general applicability of the optimized implementation across different heterogeneous GPU computing platforms.