On Thu, Jan 21, 2021 at 11:36 PM Aaron Friesz <[email protected]> wrote:
1 ) In order to fix this it is stated that a change can be made in FFTXlib/fft_param.f90. > This implies that it must then be recompiled. Is this correct? (I'd rather > avoid this as it will make me responsible for maintaining the software, > instead of our computing resources division.) > if the origin of your problem is the one descripted in the thread ( guess so), the proper fix is this one: https://lists.quantum-espresso.org/pipermail/users/attachments/20190425/2584418a/attachment.obj and yes, you have to recompile. Alternatively: &system ... force_symmorphic=.true. ... / will not look for symmetry operations with associated fractional translations and should solve the problem. Alternatively, install a newer version. If you really want to allow FFT dimensions > 2048 (the hard-coded value; 5076 is what you have) you have to modify the code and recompile. Note that the typical real-space resolution is something of the order 0.1 A, so 2048 corresponds to approx. 200 A cell side: quite a big cell The FFT is three-dimensional, so each one-dimensional FFTis very fast, but you need a bunch of them! Paolo 2 ) Is the number in parentheses, (5076), the number of terms in the fft? > Are there any heuristics to reducing this number short of reducing the > number of atoms in the system? > > 3 ) Why is this check made? Is the FFT computed in every loop of the > algorithm, thus incurring a large computational cost? (From what I remember > FFTW should be very fast on arrays of this size, but if it is calculated > often that could be an issue.) > > Thank you for your help! > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 206, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
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