[CP2K-user] [CP2K:19300] FFT problems with large unit cell

[Léon Luntadila Lufungula]

Dear Prof. Hütter,

Thanks for the suggestion I'll switch to FFTW3 then, but I do still have 
one question about using FFTW3. Why do I get the error  "the FFT in the x 
direction is not allowed n01 dimension 175" when switching from 
FFTSG/EXTENDED to FFTW3/EXTENDED, while I get an "Index to radix array not 
found." error when switching of EXTENDED_FFT_LENGHTS?

Kind regards,
Léon



On Wednesday, 4 October 2023 at 09:35:36 UTC+2 Jürg Hutter wrote:

> Hi
>
> there is an upper limit for the FFT length for the FFTSG library (1024).
> I would switch to FFTW3 where no such limit exists.
>
> regards
> JH
>
> ________________________________________
> From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of Léon 
> Luntadila Lufungula <Leon.luntad... at uantwerpen.be>
> Sent: Tuesday, October 3, 2023 2:06 PM
> To: cp2k
> Subject: [CP2K:19284] FFT problems with large unit cell
>
> Dear all,
>
> I am running some tests with long chain adsorbates on a TiO2 slab and I'm 
> running into some problems with the FFT libraries. I initially had the 
> FFTSG set as preferred library, because the manual stated that "The use of 
> PREFERRED_FFT_LIBRARY FFTSG is required" when using the WAVELET solver. 
> However, I just read in this post<
> https://groups.google.com/g/cp2k/c/QEveWI7UqV0> from Prof. Hütter that 
> you can use the FFTW3 library in combination with the WAVELET solver and I 
> already read several times that using this library is generally faster 
> compared to the internal FFTSG one. I also already had to enable the 
> EXTENDED_FFT_LENGTHS option for calculations with smaller (10x10x30) cells 
> as I ran into some "Index to radix array not found."-errors.
>
> Now, with these long adsorbates I have a cell of around 10 x 15 x 60 Å and 
> the combination of FFTSG/EXTENDED_FFT_LENGTHS again gives "Index to radix 
> array not found."-errors, while switching to FFTW3/EXTENDED_FFT_LENGHTS 
> says that "the FFT in the x direction is not allowed n01 dimension 175".
>
> So I have two questions:
> 1) Is it possible to calculate such a large cell without getting these FFT 
> errors or is it just too large?
> 2) Should I switch to FFTW3/EXTENDED_FFT_LENGTHS to speed up my 
> calculations or is it fine to continue with FFTSG/EXTENDED_FFT_LENGTHS?
>
> Hopefully someone can help me out with this problem.
>
> All the best,
> Léon
>
>
> --
> You received this message because you are subscribed to the Google Groups 
> "cp2k" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
> email to cp2k+uns... at googlegroups.com<mailto:cp2k+uns... at googlegroups.com
> >.
> To view this discussion on the web visit 
> https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%40googlegroups.com
> <
> https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%40googlegroups.com?utm_medium=email&utm_source=footer
> >.
>

-- 
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+unsubscribe at googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/acbeac79-87b6-4a21-8dfe-e4b978507655n%40googlegroups.com.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20231004/2fd8a628/attachment-0001.htm>