[Q-e-developers] diagonalization with multithreads libs slow: comparison between Jade (cines) and Fermi (cineca)

[Layla Martin-Samos]

Dear all, I have made some test calculations on Fermi and Jade, for a 107
atoms system, 70 Ry cutoff for wfc, 285 occupied bands and 1 kpoint. What
the results seems to show is that the diagonalization with multithreads lib
seems to considerably slowdown the diagonalization time (diaghd is called
33 times on all the jobs and the final results are identical). The compiled
cineca version gives identical time and results than 5.0.1.  Note that jade
in sequential is faster than BGQ. I am continuing some other tests on jade,
unfortunatelly the runs stay a lot of time in the queue, the machine is
full and even for a 10 min job with 32 cores you wait more than 3 hours. As
attachement I put the two make.sys for jade.


omputer   mpi process     threads    ndiag   complex/gamma_only   time for
diaghg    version   Libs

 bgq         128             4          1      complex (cdiaghg)
                     69.28 s      5.0.1     threads
bgq          128             4          1      complex
(cdiaghg)                                 69.14 s      4.3.2     threads

 jade         32             1          1      complex
(cdiaghg)                                  27.44 s      4.3.2     sequential
 jade         32             1          1      complex
(cdiaghg)                                 > 10 min     4.3.2     threads
 jade         32             1          1      complex
(cdiaghg)                                 > 10 min     5.0.1     threads


bgq          128             4          4      complex
(cdiaghg)                                310.52 s      5.0.1    threads

bgq          128             4          4      gamma
(rdiaghg)                                    73.87 s      5.0.1    threads
bgq          128             4          4      gamma
(rdiaghg)                                    73.71 s      4.3.2    threads

bgq          128             4          1      gamma (rdiaghg)
                  CRASH 2 it     5.0.1    threads
bgq          128             4          1      gamma
(rdiaghg)                               CRASH 2 it     4.3.2    threads


did someone observe a similar behavior?

cheers

Layla
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