In systems with a difficult self-consistency, it is possible that the
small numerical differences, coming from execution on different numbers
of processors, are sufficient to drive the system towards
non-convergence, or convergence towards a different final state (DFT+U
seems to be especially unstable in this respect).
If you are using some exotic, little tested feature, it is conceivable
that some overlooked bug in parallelization exists. In this case, the
problem is easily reproducible and clearly bound to a specific feature,
though.
I do not see any other possibility
Paolo
On 28/11/2022 17:05, Mahmoud Payami Shabestari via users wrote:
Hi All,
I am experiencing that the success in scf cycle depends on the number of
processes used in mpirun. That is, for example, for a given scf input
when I use "mpirun -np *2* pw.x < input.in",
it gives the converged result in a reasonable number of iteration; but,
on the other hand, if I instead use "mpirun -np *8* pw.x < input.in",
the system does not converge numerically.
First I thought it is somehow a problem of numerical error accumulation.
So, I used in compilation of QE the FFTW3 as prescribed in the manual.
And even used "-lfftw3l" (long-double) to cure this problem, but some
other numerical problems happened in vc-relax job.
I would appreciate if anybody helps to understand the roots of this
dependency and how to control it.
Bests,
Mahmoud Payami
NSTRI, AEOI, Tehran, Iran
Email: [email protected]
Phone: +98 (0)21 82066504
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216
_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
