[Beowulf] Theoretical vs. Actual Performance

Joe Landman joe.landman at gmail.com
Thu Feb 22 15:01:06 PST 2018

ACML is hand coded assembly.  Not likely that OpenBLAS will be much 
better.  Could be similar.  c.f. 

On 02/22/2018 05:48 PM, Prentice Bisbal wrote:
> Just rebuilt OpenBLAS 0.2.20 locally on the test system with GCC 
> 6.1.0, and I'm only getting 91 GFLOPS. I'm pretty sure OpenBLAS 
> performance should be close to ACML performance, if not better. I'll 
> have to dig into this later. For now, I'm going to continue my testing 
> using the ACML-based build and revisit the OpenBLAS performance later.
> Prentice
> On 02/22/2018 05:27 PM, Prentice Bisbal wrote:
>> So I just rebuilt HPL using the ACML 6.1.0 libraries with GCC 6.1.0, 
>> and I'm now getting 197 GFLOPS, so clearly there's a problem with my 
>> OpenBLAS build. I'm going to try building OpenBLAS without the 
>> dynamic arch support on the machine where I plan on running my tests, 
>> and see if that version of the library is any better.
>> Prentice
>> On 02/22/2018 09:37 AM, Prentice Bisbal wrote:
>>> Beowulfers,
>>> 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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Joe Landman
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