[Pw_forum] Energy variations in noncolin-constrain_total.in with OpenMP & MKL

Paolo Giannozzi p.giannozzi at gmail.com
Tue Jan 26 21:02:17 CET 2016

> One should obtain the same numbers - within the errors due to roundoff,
> though -  in serial, OpenMP, MPI execution, and on different machines, and
> with different compilers and mathematical libraries.

... actually, only at exact convergence, at least when using default
wavefunction initialization: small differences come from different
randomization of atomic wavefunctions. These however disappear as
convergence is made tighter (but sometimes they don't)

Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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