<div dir="auto"><div>Ín Wien2k the time spent in the FFT is small in all cases that I know of, particularly if you exploit mpi/omp, plus we don't use the algorithms that explore different methods. If you are going to use it for other codes (plane wave) then you might want to post to the fftw list for help. Or read <a href="http://configure.ac">configure.ac</a> to work out what is being looked for, then check your gcc/icc/icx. The second option requires a fair bit of coding expertise, be warned!</div><div><br></div><div data-smartmail="gmail_signature">___<br>Emeritus Professor Laurence Marks (Laurie)<br>Department of Materials Science and Engineering, Northwestern University<br><a href="http://www.numis.northwestern.edu">www.numis.northwestern.edu</a><br>"Research is to see what everybody else has seen, and to think what nobody else has thought" Albert Szent-Györgyi</div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Mar 4, 2025, 08:39 Michael Fechtelkord via Wien <<a href="mailto:wien@zeus.theochem.tuwien.ac.at">wien@zeus.theochem.tuwien.ac.at</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
<div>
<p>Dear all,</p>
<p>when I configure fftw 3.3.10 using:</p>
<p><span style="font-family:monospace"><span style="color:#000000;background-color:#ffffff">C=ifx F77=ifx
CC=gcc CFLAGS="-O3 -march=native -mavx2" FCFLAGS="-O3 -xAVX2"\<br>
./configure --prefix=/usr/local/ --enable-shared
--enable-mpi --enable-openmp --enable-threads --enable-avx
--enable-avx2</span></span></p>
<p><span style="font-family:monospace"><span style="color:#000000;background-color:#ffffff"><br>
</span></span></p>
<p><span style="font-family:monospace"><span style="color:#000000;background-color:#ffffff">I get a
warning from configure:</span></span></p>
<p><span style="font-family:monospace"><span style="color:#000000;background-color:#ffffff"><br>
</span></span></p>
<p><span style="font-family:monospace"><span style="color:#000000;background-color:#ffffff">checking
whether a cycle counter is available... no </span><br>
***************************************************************
<br>
WARNING: No cycle counter found. FFTW will use ESTIMATE mode <br>
for all plans. See the manual for more information. <br>
***************************************************************</span></p>
<p>I am using gcc 14.2, ifx 2025.0 on opensuse leap 15.6</p>
<p>I am not sure if I had this in older versions of gcc / ifort. <br>
</p>
<p>My question: Is the estimate mode a performance problem or can I
just neglect the warning?</p>
<p><br>
</p>
<p>Best regards,</p>
<p>Michael<br>
</p>
<p><br>
</p>
<pre cols="72">--
Dr. Michael Fechtelkord
Institut für Geologie, Mineralogie und Geophysik
Ruhr-Universität Bochum
<a href="https://www.google.com/maps/search/Universit%C3%A4tsstr.+150?entry=gmail&source=g">Universitätsstr. 150</a>
D-44780 Bochum
Phone: +49 (234) 32-24380
Fax: +49 (234) 32-04380
Email: <a href="mailto:Michael.Fechtelkord@ruhr-uni-bochum.de" target="_blank" rel="noreferrer">Michael.Fechtelkord@ruhr-uni-bochum.de</a>
Web Page: <a href="https://www.ruhr-uni-bochum.de/kristallographie/kc/mitarbeiter/fechtelkord/" target="_blank" rel="noreferrer">https://www.ruhr-uni-bochum.de/kristallographie/kc/mitarbeiter/fechtelkord/</a>
</pre>
</div>
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