[CP2K-user] [CP2K:20974] Resolving MPI limitations with the wavelet Poisson solver for a large system

[Xing Wang]

Hi community,

I am running a calculation on a system with 480 atoms in a unit cell of 
size approximately 37×37×37 Å. I used 128 CPUs with the wavelet Poisson 
solver, but encountered the following error:

*******************************************************************************
*   ___                                                                     
  *
*  /   \                                                                   
   *
* [ABORT]  Index out of range in wavelet solver. Try decreasing the number 
of *
*  \___/      MPI processors, or adjust the PW_CUTOFF or cell size so that 
   *
*    |       2*(number of RS grid points) matches the allowed FFT 
dimensions  *
*  O/|                      (see ps_wavelet_fft3d.F) exactly.               
  *
* /| |                                                                     
   *
* / \                                                 
ps_wavelet_kernel.F:996 *
*******************************************************************************

I tried reducing the number of CPUs to 48, and the calculation ran 
successfully. However, given the large system size, the calculation is very 
slow with fewer CPUs.

My Questions:
- Is there a way to use more CPUs with the Wavelet solver without 
encountering the FFT grid error?
- Are there specific strategies (e.g., adjusting PW_CUTOFF, hybrid 
MPI+OpenMP) to ensure FFT grid compatibility while improving 
parallelization efficiency?

Any suggestions would be greatly appreciated!

Best regards,
Xing

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