Dear Prof. Hutter,<div><br /></div><div>First off, my apologies for writing your surname incorrectly. I was so focussed on not forgetting the umlaut that I seem to have placed it on the wrong part of your name.</div><div><br /></div><div>Second, changing the source might be an option for local calculations but implementing this change on our HPC cluster is very cumbersome as I have discovered a while back when doing something similar with Quantum ESPRESSO. Therefore, I think I'll try forcing a common grid for the troublesome calculations, but I am not sure how to do this in practice. I searched the mailing list and documentation for common grid size, but could not find the correct option. Could you point me in the right direction for this?</div><div><br /></div><div>Kind regards,</div><div>Léon</div><div><br /></div><div>P.S. Thanks for the descriptive answers, they really help me understand the program and how to improve my input files!<br /><br /></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Tuesday, 10 October 2023 at 13:23:37 UTC+2 Jürg Hutter wrote:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi <br> <br>the wavelet solver uses its own FFT library. The calculation then requires that <br>the number of grid points is allowed for both, the FFT library used in CP2K and <br>in the wavelet solver code. For smaller lengths that is no problem. For larger ones the FFTSG is not available and FFTW3 might use different roots. <br> <br>Possible solution (I haven't done any tests): <br>Change in src/pw/fft/fftw3_lib.F <br> <br> maxn_threes = 6 <br> maxn_fives = 5 <br> maxn_sevens = 0 <br> maxn_elevens = 0 <br> maxn_thirteens = 0 <br> <br>If this doesn't work for some a/b/c settings, force a common grid size in the input. <br> <br>regards <br>JH <br> <br>PS: Please check the correct writing of my name, thank you. <br> <br>________________________________________ <br>From: <a href data-email-masked rel="nofollow">cp...@googlegroups.com</a> <<a href data-email-masked rel="nofollow">cp...@googlegroups.com</a>> on behalf of Léon Luntadila Lufungula <<a href data-email-masked rel="nofollow">Leon.luntad...@uantwerpen.be</a>> <br>Sent: Tuesday, October 10, 2023 11:10 AM <br>To: cp2k <br>Subject: Re: [CP2K:19336] FFT problems with large unit cell <br> <br>Dear Prof. Hütter, <br> <br>I quickly want to summarize the errors I've had in hope that you can provide some answers as to why these happen and how I can fix them. <br> <br>So I ran some calculations of a 1x4x3 anatase (101) slab with different vacuum thicknesses [a = 10 Å, b = 20-70 Å, c = 15 Å (XZ periodicity for wavelet solver)] and tried the following combinations of FFT libraries which resulting in the errors stated below: <br> <br>1) FFTSG + EXTENDED_FFT_LENGTHS: fails for b = 70 Å with an "Index to radix array not found"-error <br>2) FFTW3 + EXTENDED_FFT_LENGTHS: fails at every value of b with "the FFT in the x direction is not allowed; n01 dimension 175"-error <br>3) FFTW3: fails for b = 70 Å with an "Index to radix array not found"-error <br> <br>From what you've told me I plan on going with the FFTW3 library from now on, but it does still fail with a sufficiently large box when EXTENDED_FFT_LENGTHS is disabled, but enabling this option makes the problem even worse as then the calculation fails no matter the size of the unit cell... <br> <br>So my question is why does the FFTW3 library give an Index error when you stated that it does not have an upper limit and why then does enabling the EXTENDED_FFT_LENGTHS result in the other error stated above? <br> <br>Best regards, <br>Léon <br> <br>On Wednesday, 4 October 2023 at 09:57:02 UTC+2 Léon Luntadila Lufungula wrote: <br>Dear Prof. Hütter, <br> <br>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? <br> <br>Kind regards, <br>Léon <br> <br> <br> <br>On Wednesday, 4 October 2023 at 09:35:36 UTC+2 Jürg Hutter wrote: <br>Hi <br> <br>there is an upper limit for the FFT length for the FFTSG library (1024). <br>I would switch to FFTW3 where no such limit exists. <br> <br>regards <br>JH <br> <br>________________________________________ <br>From: <a href data-email-masked rel="nofollow">cp...@googlegroups.com</a> <<a href data-email-masked rel="nofollow">cp...@googlegroups.com</a>> on behalf of Léon Luntadila Lufungula <<a href data-email-masked rel="nofollow">Leon.luntad...@uantwerpen.be</a>> <br>Sent: Tuesday, October 3, 2023 2:06 PM <br>To: cp2k <br>Subject: [CP2K:19284] FFT problems with large unit cell <br> <br>Dear all, <br> <br>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<<a href="https://groups.google.com/g/cp2k/c/QEveWI7UqV0" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en-GB&q=https://groups.google.com/g/cp2k/c/QEveWI7UqV0&source=gmail&ust=1697033401054000&usg=AOvVaw1kz8kxEAu_q2xZY22Itln6">https://groups.google.com/g/cp2k/c/QEveWI7UqV0</a>> 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. <br> <br>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". <br> <br>So I have two questions: <br>1) Is it possible to calculate such a large cell without getting these FFT errors or is it just too large? <br>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? <br> <br>Hopefully someone can help me out with this problem. <br> <br>All the best, <br>Léon <br> <br> <br>-- <br>You received this message because you are subscribed to the Google Groups "cp2k" group. <br>To unsubscribe from this group and stop receiving emails from it, send an email to <a href data-email-masked rel="nofollow">cp2k+uns...@googlegroups.com</a><mailto:<a href data-email-masked rel="nofollow">cp2k+uns...@googlegroups.com</a>>. <br>To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%40googlegroups.com" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en-GB&q=https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%2540googlegroups.com&source=gmail&ust=1697033401054000&usg=AOvVaw1bK_leG09L_77Qa-S_gduM">https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%40googlegroups.com</a><<a href="https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%40googlegroups.com?utm_medium=email&utm_source=footer" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en-GB&q=https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%2540googlegroups.com?utm_medium%3Demail%26utm_source%3Dfooter&source=gmail&ust=1697033401054000&usg=AOvVaw3B6vRe_x8EGgX-lugMDl0I">https://groups.google.com/d/msgid/cp2k/38650355-0f22-4606-82bb-16a670bc8619n%40googlegroups.com?utm_medium=email&utm_source=footer</a>>. <br> <br>-- <br>You received this message because you are subscribed to the Google Groups "cp2k" group. <br>To unsubscribe from this group and stop receiving emails from it, send an email to <a href data-email-masked rel="nofollow">cp2k+uns...@googlegroups.com</a><mailto:<a href data-email-masked rel="nofollow">cp2k+uns...@googlegroups.com</a>>. <br>To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/e97d9f8a-ac3e-4cf6-adf7-4e32cfc9010fn%40googlegroups.com" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en-GB&q=https://groups.google.com/d/msgid/cp2k/e97d9f8a-ac3e-4cf6-adf7-4e32cfc9010fn%2540googlegroups.com&source=gmail&ust=1697033401054000&usg=AOvVaw15xXY9evbRTplSRYoUOzcL">https://groups.google.com/d/msgid/cp2k/e97d9f8a-ac3e-4cf6-adf7-4e32cfc9010fn%40googlegroups.com</a><<a href="https://groups.google.com/d/msgid/cp2k/e97d9f8a-ac3e-4cf6-adf7-4e32cfc9010fn%40googlegroups.com?utm_medium=email&utm_source=footer" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en-GB&q=https://groups.google.com/d/msgid/cp2k/e97d9f8a-ac3e-4cf6-adf7-4e32cfc9010fn%2540googlegroups.com?utm_medium%3Demail%26utm_source%3Dfooter&source=gmail&ust=1697033401054000&usg=AOvVaw3oEPQB1ZcKNs-bP0CNT7iG">https://groups.google.com/d/msgid/cp2k/e97d9f8a-ac3e-4cf6-adf7-4e32cfc9010fn%40googlegroups.com?utm_medium=email&utm_source=footer</a>>. <br></blockquote></div> <p></p> -- <br /> You received this message because you are subscribed to the Google Groups "cp2k" group.<br /> To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>.<br /> To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/a3612a0e-35e9-45ca-9664-eed48a6dd7efn%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/a3612a0e-35e9-45ca-9664-eed48a6dd7efn%40googlegroups.com</a>.<br />