[QE-users] [QE-GPU] Significant Slowdown in GPU Phonon Calculation Preparation

[Yin-Ying Ting]

Dear Quantum Espresso Experts,

I've been running a phonon calculation using QE-7.2 on both CPU and GPU and have noticed significantly different runtimes in the preparation step. I'd appreciate insights on how to improve the GPU performance.


CPU Setup:
    Nodes: 8
    Cores per Node: 128
    Parallelization: 8 images, 4 npools (calculation has 4 k-points)

GPU Setup:
    Nodes: 8
    GPUs per Node: 4
    OMP_NUM_THREADS: 1
    Parallelization: 8 images, 4 npools (calculation has 4 k-points)



The preparation step, including steps like "Compute atoms," "Ewald sum," and charge density calculations, took around 9 hours on the CPU setup but over 24 hours on the GPU setup. Below is a section from the CPU calculation output before computing scf of each representation mode:

----------------------------------------------------------------

     Compute atoms:     1,    2,    3,    4,    5,    6,    7,    8,
    9,   10,   11,   12,   13,   14,   15,   16,
   17,   18,   19,   20,   21,   22,   23,   24,



     Alpha used in Ewald sum =   2.8000

     negative rho (up, down):  9.781E-01 0.000E+00
     PHONON       :      8h51m CPU      8h56m WALL



     Representation #   1 mode #   1

     Self-consistent Calculation
-----------------------------------------------------------------------


Why might the preparation step for the GPU-based calculation be taking significantly longer? Are there specific optimizations or configurations I can apply to improve GPU performance in QE phonon calculations?

Thank you in advance for your help!


Best regards,

PhD student in Forschungszentrum Jülich
Yin-Ying Ting

--

Forschungszentrum Jülich GmbH
Institute of Energy and Climate Research
Theory and Computation of Energy Materials (IEK-13)
E-mail: y.ting at fz-juelich.de<mailto:y.ting at fz-juelich.de>


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