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Re^2: Help needed regarding "asynchronous file I/O","Real time data packing" etc. to boost computational speeds.

Siddheshwar Chopra
sidhusai@gmail.com


Dear Alex,
I will try out the options provided by you. Thanks for the information.

On Mon May 5 '14 2:49am, Alex Granovsky wrote
---------------------------------------------
>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.htmlhttp://classic.chem.msu.su/gran/gamess/packing.html

>and

>http://classic.chem.msu.su/gran/gamess/Firefly_input_rev002.pdfhttp://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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