[CP2K-user] [CP2K:21018] Re: Performance degregation for DCDFT starting with CP2K 2024.2

[Augustin Bussy]

Hi Ralf,

I believe this comes from a bug fix in HFX response forces: 
https://github.com/cp2k/cp2k/commit/233cc0496608329821996a6a19a46b58c16292f1#diff-e05447976b45d06ff57c2ca772d89269da230e4970b6001c4ee2f25c70584cffR428-R430. 
Before that, by default, the density matrix was used to screen the integral 
derivative, also for response forces. This is not a safe assumption, and it 
was therefore removed.

To verify this hypothesis, you can try running CP2K v2024.1 with the added 
keyword SCREEN_P_FORCES set to FALSE in the HFX%SCREENING section. This 
should make the 2 runs equally slow.

Best,

Augustin


On Wednesday, 8 January 2025 at 10:09:31 UTC+1 Ralf Frischmann wrote:

> Dear all,
>
> when running a DCDFT calculation with pre-compiled CP2K binaries from 
> GitHub, I do observe a significant reduction in overall runtime performance 
> when moving from CP2K version 2024.1 to 2024.2 (and versions beyond). 
>
> The increase occurs in ENERGY_FORCE runs only. The crucial spot seems to 
> be the execution part AFTER convergence of the gradient response solver 
> "The linear solver converged in    7 iterations." 
>
> From the HFX_MEM_INFO output, it is apparent that version 2024.2 computes 
> a somewhat larger number of "sph. DERIV's calculated on the fly" (see 
> attached outputs for a 20 water PBC cell), but the difference in my opinion 
> is too small to explain the increase in runtime of about 50% for that 
> system size. 
>
> For larger system with 32 or 64 H2O molecules, the described runtime 
> increase becomes more pronounced, reaching 250% for 64 H2O molecules.
>
> Is that expected/intended behavior?
>
> Any explanation, hint or advice would be greatly appreciated.
>
> Regards,
>
> Ralf
>
>
>
>
>
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>
>  
>
>

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