Firefly and PC GAMESS-related discussion club

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Alex Granovsky
gran@classic.chem.msu.su

>1. Energy calculation works fine. But, if we use firefly for geometry optimisation,  have next message in out file:

>*** ERROR *** GRADIENT IS AVAILABLE ONLY FOR RHF MP2 RUNS

>As we understood, this deals with impossibility of using MP4
for optimization. Can we use GPU for geometry optimization?

No you cannot use gradient optimization with MP4.
However, for small molecules you can use non-gradient
one (runtyp=trudge).

>2. In other calculation we deal with large molecular system, and we have in out file:

>*** ERROR, NO MORE THAN  2024 TOTAL SHELLS

>Is there any ways to move away this distinction?

This limit is hardcoded in the current Firefly version.
Perhaps, it will be lifted in the future releases.
However, with MP4, you'll hit the wall long before this
limit, as calculations for large systems are extremely
expensive even with your Tesla boards (which have, anyway,
the theoretical double precision performance limit of only ca.
1.5 TFlops in aggregate - that is they are equivalent to
ca. 120 cores of modern CPUs and only to 60 future AVX-enabled
cores. That's definitely not a power of huge cluster :))

Regards,
Alex Granovsky