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VASP 6.2 ACC GPU corrector takes much more time

Posted: Wed Feb 10, 2021 4:18 pm
by david_keller
Is there a reason why the timing for the "CORREC" and "EDDIAG" sections would take longer for a run using a GPU verses and identical run using only CPUs?
We are finding using the OpenACC GPU version to be beneficial as far as run times with the exception of time spent in "CORREC" corrector section and the "EDDIAG" section.

-------------------------------------- Iteration 1( 11) ---------------------------------------

GPU
POTLOK: cpu time 0.0137: real time 0.0137
SETDIJ: cpu time 0.7244: real time 0.7261
TRIAL : cpu time 1.5328: real time 1.5365
CORREC: cpu time 1.4981: real time 1.5017
EDDIAG: cpu time 0.3957: real time 0.3967
CHARGE: cpu time 0.3385: real time 0.3393

CPU
POTLOK: cpu time 0.0149: real time 0.0150
SETDIJ: cpu time 0.0562: real time 0.0563
TRIAL : cpu time 1.6162: real time 1.6201
CORREC: cpu time 0.9915: real time 0.9940
EDDIAG: cpu time 0.7746: real time 0.7817
CHARGE: cpu time 0.1655: real time 0.1660

Perhaps this section does not run on the GPU yet??