[Beowulf] Benchmark between Dell Poweredge 1950 And 1435

Richard Walsh rbw at ahpcrc.org
Thu Mar 8 12:06:00 PST 2007

Mark Hahn wrote:
> basically, 13 GB/s for a 2x2 opteron/2.8 system (peak flops would be 
> 2*2*2*2.8=22.4, so you need 1.7 flops per byte so you need 1.7 flops 
> per byte to be happy.
    Mmmm ... to my eye the Triad need 3 x 8 bytes = 24 bytes per 2 FLOP or
    12 bytes per 1 FLOP ... FLOPs per byte seems upside down as bandwidth
    Gbytes/sec are typically thought of as the scarce resource.

    The way I would do the calculation from your referenced data:

    Triad for 4 Opteron cores at 2.8 GHz  === 12889 GBytes/sec

    In 64-bit words moved that's ===  12889/8 bytes/word or 1611 GWords/sec

    The Triad does 2 FLOPs per 3 words moved (assumes 1 scalar value) ...
    so you can convert this to GFLOPS as:

    1611 GWords * .6667 =  1075  GFLOPs from the 4 cores or 268.5 MFLOPS per
    Opteron core.

    On a per core basis that is 4.7 % (ugh!) of peak on the Stream 
Triad.  So codes with
    kernels that have a low FLOP/MOP ratio (smallish with limited 
potential for
    cache re-use) watch out.  Xeon/Woodcrest would do worse on the 
Triad, better on HPL
    clock-for-clock.  This is, as Mark says, due to its "wider" CPU and 
larger cache
    (and a few other tricks that Woodcrest does with hoisting loads and 
prefetch engines).

    Hope this is useful ...





Richard B. Walsh

Project Manager
Network Computing Services, Inc.
Army High Performance Computing Research Center (AHPCRC)
rbw at ahpcrc.org  |  612.337.3467

>  "The world is given to me only once, not one existing and one
>   perceived. The subject and object are but one."
>   Erwin Schroedinger

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