Dear Lorenzo and Michel, thank you for your reply. Yes, unfortunately I am using a small cluster and, for memory issues, I cannot use the SSD-based local scratch. Thus I am forced to use a non-parallel NFS. From your answers, I understand that, given the situation, the huge difference between the CPU and WALL time that I am observing is reasonable. Since I am facing a hardware limitation I guess I cannot do much to improve the performances. I will try to find some solutions with the person in charge of the cluster.
Best Regards, Raffaello Bianco UPV/EHU - CFM On Wed, Sep 30, 2020 at 4:13 PM Michal Krompiec <[email protected]> wrote: > Dear Rafaello, > Are you using a local (preferably SSD-based) scratch drive, or a very fast > parallel file system? > Best wishes, > Michal Krompiec > Merck KGaA > > On Wed, 30 Sep 2020 at 15:05, Raffaello Bianco < > [email protected]> wrote: > >> Dear QE users and developers, >> >> I am doing an electron-phonon coupling calculation in this way (I am >> using QE v 6.6). >> First, I have done an scf calculation. Then, I have done a phonon >> calculation where I have printed the dvscf files, with >> >> fildvscf = 'dvscf' >> >> Subsequently, I have done the electron-phonon calculation changing the >> k-mesh grid, with >> >> trans = .false. >> electron_phonon = 'simple' >> >> The calculation ends correctly, but for some q points I have noticed a >> huge difference between >> CPU and Wall time, like >> >> PHONON : 15h55m CPU 3d18h56m WALL >> >> From the report at the end of the output, the I/O davcio routine seems to >> be the >> "guilty": >> >> >> General routines >> davcio : 107.89s CPU 263856.08s WALL ( 520331 calls) >> >> Parallel routines >> >> Electron-phonon coupling >> elphon : 41730.55s CPU 309708.87s WALL ( 1 calls) >> elphel : 41671.20s CPU 309625.04s WALL ( 60 calls) >> >> General routines >> davcio : 107.89s CPU 263856.08s WALL ( 520331 calls) >> >> This calculation was done with 10 processors and npool = 10, if I use 40 >> processors and npool = 10 it is worse (as can probably be expected due to >> the higher number of I / O operations). I have looked at the documentation >> but I am not very familiar with these things, thus I still have several >> doubts. Any suggestions on tests to do or how to improve performance, or at >> least comments to clarify the problem, would be greatly appreciated. >> >> Thank you for your time, >> >> Best, >> Raffaello Bianco >> >> >> _______________________________________________ >> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) >> users mailing list [email protected] >> https://lists.quantum-espresso.org/mailman/listinfo/users > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
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