PC GAMESS/Firefly-related discussion club

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Veinardi Suendo
vsuendo@chem.itb.ac.id

Actually, we are planning to expand our system to this new processor family due to its HTT. However, does this function really reduce the calculation performance? I have checked in the performance section but I could not find the benchmark that used all 8 cores (4 real cores + 4 logical cores). Is it comparable the performance of one Core i7 machine with 2 Core2 machines? If you do not mind would you explain more about Firefly options using HTT. Normally, in Core 2 Quad based machine, I use only:

$P2P p2p=.t. dlb=.t. xdlb=.t. mxbuf=2048 $END
$SMP Call64=.t. httpar=.t. httalt=.t. $END

How about in Core i7 machine? Should I add more option in $SMP section such the following?

$SMP Call64=.t. httpar=.t. httalt=.t. httfix=.t. $END

Thank you very much in advance,

Best regards,

Veinardi

On Wed Apr 8 '09 0:27am, Alex Granovsky wrote
---------------------------------------------
>Dear PC GAMESS/Firefly users,

>Recent Intel's Nehalem core processors (e.g., Core i7/Xeon 5500/Xeon 3500)
>reimplement hyper-threading technology, which does result in some performance improvements
>(see results of our tests in the "Performance" section).

>Unfortunately, as of moment of writing this note (April 2009),
>both Windows and Linux are not capable to identify correctly
>the particular logical processors belonging to each specific CPU
>core. In practice this confuses tasks/threads scheduler and
>results in performance degradation of parallel or multithreaded jobs
>while running with HTT turned on.

>This was found for Windows Vista/Windows Server 2008 and most likely
>affects older versions of Windows as well. As of now, all modern
>Linux distributions with their default kernels are also affected.
>
>
>The reason of this is most likely the changed semantics of some CPUID functions.

>This problem, however, does not affect Firefly running with httfix
>option turned on (see http://classic.chem.msu.su/gran/gamess/smp.htmlhttp://classic.chem.msu.su/gran/gamess/smp.html
>for details on this option).
>
>
>This option is turned on under Windows by default; however, to use it
>under Linux, one needs to upgrade to Firefly version 7.1.E or above
>and turn it on manually.
>
>
>In addition, one may need to provide correct -ncores and -nthreads command line arguments
>(see http://classic.chem.msu.su/gran/gamess/comm_line.htmlhttp://classic.chem.msu.su/gran/gamess/comm_line.html for details),
>e.g. if running Firefly in environment with CPUID instruction virtualized.
>For example, MS Hyper-V (and perhaps some other modern virtualization solutions)
>virtualizes CPUID instruction thus limiting the amount of information available to Firefly.
>This affects Firefly running both in the virtual machines and on the host OS itself.

>Alternatively, one may disable HTT at all. As to Firefly running
>using correct options described here, this will result in some
>performance degradation. However, this may improve performance of
>other programs one may need to use.

>Best regards,
>Alex Granovsky
>
>
>