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Re: Help needed regarding "asynchronous file I/O","Real time data packing" etc. to boost computational speeds.

Alex Granovsky
gran@classic.chem.msu.su


Dear Siddheshwar,

Most likely you did not see any effect due to async I/O and real time
file packing (i.e. compression) because you are running direct jobs.

Try to run large conventional (i.e. disk based) HF job. First, set:

 $system async=0 $end
 $intgrl packao=.f. $end

then

 $system async=1 $end
 $intgrl packao=.f. $end

then

 $system async=0 $end
 $intgrl packao=.t. $end

then

 $system async=1 $end
 $intgrl packao=.t. $end

Save outputs, compare execution times, and compare size of "aoints" files.

>In the manual it says that asynchronous file I/O is by default OFF in Linux.. Why so? and why is it ON for Windows?

Asynchronous file I/O is off under Linux by default mainly due to
compatibility problems with old buggy Linuxes. Presently, it is safe
to use this option under Linux.

It is turned on under Windows by default because there were not any
compatibility problems reported so far and because the performance
gain due to its use is more significant under Windows OS.  

> Does option "ASYNC=2" seem better?

There is only a subtle difference between ASYNC=2 and ASYNC=1

>What is Realtime data packing and how to control it?

The real time data packing (real time data compression) uses very fast
and efficient data compression methods in order to compress data
before storing them on the disk and decompress them back when reading
them from disk. See:

http://classic.chem.msu.su/gran/gamess/packing.html

and

http://classic.chem.msu.su/gran/gamess/Firefly_input_rev002.pdf

(search for PACKAO, FASTCI, and PACK2 keywords).

Hope this helps.

Kind regards,
Alex Granovsky



On Tue Apr 29 '14 8:18am, Siddheshwar Chopra wrote
--------------------------------------------------
>Dear Firefly users,
>I would be grateful if anyone could explain the use of "asynchronous file I/O","Real time data packing" and Dynamic load balancing, to boost the computation speeds. Actually I went through a ppt about Firefly where all these features when switched on, resulted in very high speeds (for a fullerene dimer). DLB seems okay to me, but others are not.
>In the manual it says that asynchronous file I/O is by default OFF in Linux.. Why so? and why is it ON for Windows? Does option "ASYNC=2" seem better?
>What is Realtime data packing and how to control it?

>Thanks in advance,

>Kind Regards,


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