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Re^2: Direct SCF vs conventional SCF

Alex Granovsky
gran@classic.chem.msu.su


Hi again,

the somewhat outdated document discussing these problems can be found here

http://classic.chem.msu.su/gran/gamess/marek/en/docs/PCG-Tutorial-Hardware.pdf

Kind regards,
Alex Granovsky


On Sun Jan 13 '13 1:56am, Alex Granovsky wrote
----------------------------------------------
>Dear Denis,

>sorry I do not have a definite answer to your question.

>I personally prefer direct SCF and I think most of our users
>use direct SCF for HF and DFT. On the other hand I know some
>users who use RAID arrays built of inexpensive SSDs.

>As to memory, Filrefly is limited by ca. 490 MWords of RAM
>per process i.e. a parallel run can use lots of memory.

>Kind regards,
>Alex Granovsky

>On Fri Jan 11 '13 3:22pm, Denis Zavelev wrote
>---------------------------------------------
>>Hello again!

>>Perhaps it's stupid question but nevertheless I'd like to ask it...
>>Today CPUs and GPUs are fast enough and in many cases we can use DIRSCF=.t. thus avoiding using HDDs/SSDs for temporary data read/write and speeding up the computations. From the other side, today's SSDs are fast enough (and many of them can use SATA 3.0) so data transfer speed won't be definitely limiting factor. SSDs are not cheap so I'd like to ask (as I'm choosing new workstation or even 2 workstations) in which cases conventional SCF should be used instead of direct SCF for any reasons? In particular case (workstation + typical task) it's not a problem to test both cases and compare the results, but the situation is not such: I haven't got new workstation yet, so I'd like to know whether I need several SSDs or not.
>>BTW, is Firefly 8.0.0 able to use more than 3.3Gb of RAM (i.e. up to 3.3Gb/process)?


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