Firefly and PC GAMESS-related discussion club

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Alex Granovsky
gran@classic.chem.msu.su

this question is really important, at least for every Firefly
users running it under Windows 7 on Nehalem processors (i.e.,
Core i7, Xeon 3500, Xeon 5500 etc...).

Actually, all the retail versions of Windows 7 we tested so far
(we did not test Win2K8 R2 as of yet) have the nasty kernel bug
that causes really weird things to happen if the process has an
explicit CPU affinity mask set. This causes dramatic performance
degradation if one is running PC GAMESS or Firefly in parallel on
e.g. Core i7 system with hyper-threading enabled. There are two
workarounds available at moment. The first one is to disable
hyperthreading in BIOS. The second one is to set $smp httfix=0 smppar=1 $end
and always run Firefly in parallel using all available logical,
not physical cores. The latter would mean that you may need up
to 8 physical disks (or a couple of SSDs) for disk-intensive tasks
like MP2 code.

Another workaround is to resort to Windows Vista or Win2K8 R1...

We are working with MS to resolve this issue. Actually,
Windows kernel team has been notified on this problem and
most likely MS will provide a fix to this problem soon enough.

Hope this helps.

Regards,
Alex Granovsky


On Tue Dec 29 '09 1:21am, Fa-Gung Fan wrote
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>Dear Firefly/PC GAMESS Users:

>I recently obtained a Core i7 920 system, and opted to use Windows 7 Enterprise edition 64-bit.  As soon as the system was up, I read this post of Dr. Monev regarding the performance of Windows 7 vs. Vista for Firefly/PC GAMESS calculations.  I thought “Oops, I might have made a mistake, should have selected Vista instead.”  

>I would like to ask on this forum, since Dr. Monev’s experience with Windows 7 RC in August, has someone investigated the OS’ performance (especially, the released editions) for Firefly/PC GAMESS?  Please post your experiences and suggestions.  Thank you very much.
>
>
>               Fa-Gung Fan
>
>
>On Sat Aug 1 '09 3:12pm, Valentin Monev wrote
>---------------------------------------------
>>Dear Professor Granovsky,
>>I compared wall times for mp2 optimization runs for two identical pc’s (core i7 cpu 920 6GB ram 2x1TB hdds, hyperthreading and turbo-boost enabled) under windows 7 (RC) and vista (both ultimate, 64 bit). To my surprise, the windows 7 wall times were twice or more greater than the Vista wall times – see attached files (1 input, 2 output files). In addition, running the same input in a row under windows 7, I obtained wildly different wall times. To exclude any hardware problems, I replaced 7 with vista, and the wall times became stable and comparable to those for vista on the other pc. I reinstalled windows 7, this time with the 2 hard disks in raid0 (intel ich10r, enabled write caching, turned off windows write-cache buffer flushing), for additional convenience and performance benefits. Again, wall times became unstable and much longer than those for the vista system.
>>As advised by you (http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C34df668afbHW-7096-1266+00.htm), I used a single fixed logical processor per core, and the default $smp values (see attached files). [Previously, I had tried using 7 logical processors out of the total 8 available ($smp httfix=.f. httpar=.t. smppar=.t. $end.)  In fact, this was often much faster per point, but overall the gradients tended to decrease faster i.e. final results were obtained faster in the case of just 1 logical processor per core (4 fixed logical processors). Additional benefits of 4 fixed logical processors: a) the pc is loaded just 50nstead of 89řabout 8 degrees centigrade cooler, and the pc is more responsive for interactive work), b) in (next) version G of firefly, “SMT enabled parts of the program” (http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C34df668afbHW-7096-1268+00.htm) will further utilize the second (free) logical processor.]
>>I tried many combinations of options described in the (new) mp2 documentation. For example, leaving out the line $mp2 ioflgs(1)=65536,65536 ioflgs(3)=65536,65536 $end led to the memory becoming occupied 99°and the pc became totally unfit for interactive work, while the performance issue was even aggravated. Leaving out XDLB=.T., and/or mxbuf=2048, did not help either. Restarting the pc sometimes seemed to worsen the performance, which is strange.
>>To summarize, I have no idea what is different in windows 7 relative to vista, but it seems tuning of firefly may be needed for the new operating system.
>>Of course I realize that it may be asking too much for you to tune the program for an operating system that is yet to come out in October 2009. But I could run the program with various options suggested by you…
>>Thank you in advance.
>>