[QE-users] MPI & OpenMP - CPU and WALL TIME in QE 6.5

[IORI, Federico]

Dear all .
I am doing some scalability test with MPI/OpenMP on QE 6.5 compile on IRENE
skylake cluster at CEA (France).
I noticed that (as in a past version of QE) I have an apparently  "weird"
discrepancy between the WALL time and the CPU time at the end of the
calculation.

(QE 6.5 Intel 2017 + ELPA 2016 )
480 mpi processes * N_omp_threads:

pw.out_480tasks_1omp:     PWSCF        :  20m54.92s CPU  21m47.65s WALL
pw.out_480tasks_2omp:     PWSCF        :  28m 2.16s CPU  16m11.73s WALL
pw.out_480tasks_3omp:     PWSCF        :  35m43.95s CPU  14m12.05s WALL
pw.out_480tasks_4omp:     PWSCF        :  43m24.46s CPU  13m16.07s WALL
pw.out_480tasks_5omp:     PWSCF        :  54m59.95s CPU  13m44.10s WALL
pw.out_480tasks_6omp:     PWSCF        :      1h 1m CPU  12m33.37s WALL
pw.out_480tasks_7omp:     PWSCF        :      1h12m CPU  13m28.96s WALL
pw.out_480tasks_8omp:     PWSCF        :      1h19m CPU  12m41.74s WALL

The WALL TIME seems to be the WALL TIME for 1 omp threads in every run.
To that the CPU TIME = WALL TIME * N_omp_threads

It this correct according to your experience or not?
Thanks in advance.
Best regards


-- 
Federico IORI

Computational material scientist

Paris Innovation Campus

1 chemin de la Porte des Loges
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Tel: +33(0) 6 72 03 66 19 - Mail: federico.iori at airliquide.com
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