[Beowulf] Theoretical vs. Actual Performance
pbisbal at pppl.gov
Thu Feb 22 10:50:54 PST 2018
This is my source for those theoretical numbers:
If those numbers are off, that makes my job a bit easier. And it looks
like you're right. In the text above the table, it does mention 2-socket
servers, and then below the table in fine print, it states
"For AMD Opteron Processors, theoretical FLOPS = Core Count x Core
Frequency x number of processors per server x 4."
Why can't the table just show single socket performance? Grrrr....
Regardless of bad marketing and graphics design, I'm still at at square
one. My system has 2 sockets, and the best I've been able to do is get
~115 GFLOPS. And that's one of the 'instaneous' values LINPACK spits out
every few seconds. At the end of test, the actual GFLOPS result is more
like 77 GLOPS:
T/V N NB P Q Time Gflops
WR00L2L2 82775 40 4 8 4924.71 7.678e+01
This is a two socket system, so that's only 27% of theoretical max.
On 02/22/2018 01:18 PM, Dmitri Chubarov wrote:
> not sure if the 282 GFLOPS number is correct.
> We have 16 Bulldozer/Interlagos cores at 2.2 GHz. Each pair of cores
> forms a CMT module. The two cores in the module share an FPU with 2
> 128-bit FMAC units.
> In terms of double precision FLOPS it should make
> 16 * 2.2GHz * 2 double precision scalars/SIMD register * 2 FLOPS / FMA
> op = 140.8 GFLOPS
> It looks like 282 GFLOPS number is per a 2P node.
> On 22 February 2018 at 21:37, Prentice Bisbal <pbisbal at pppl.gov
> <mailto:pbisbal at pppl.gov>> wrote:
> In your experience, how close does actual performance of your
> processors match up to their theoretical performance? I'm
> investigating a performances issue on some of my nodes. These are
> older systems using AMD Opteron 6274 processors. I found
> literature from AMD stating the theoretical performance of these
> processors is 282 GFLOPS, and my LINPACK performance isn't coming
> close to that (I get approximately ~33% of that). The number I
> often hear mentioned is actual performance should be ~85%. of
> theoretical performance is that a realistic number your experience?
> I don't want this to be a discussion of what could be wrong at
> this point, we will get to that in future posts, I assure you!
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