[Beowulf] Linpack and peak performance
gmichal at uow.edu.au
Thu Feb 7 05:18:18 EST 2008
We set up our first cluster in our faculty this week. As we are new to
cluster computing, there is a lot to learn. We performed some linpack test
using the OpenMPI benchmark available in the Rocks 4.3 distribution. The
system is as follow:
- GigB ethernet with switch HP Procurve 2800 series
- 1 Master node: 500GB sata HDD, two intel quad core E5410 at 2.33GHz, 2GB
- 4 nodes each having: 80GB sata HDD, two intel quad core E5410 at 2.33GHz,
First I'm a bit confused by the parameters P and Q in HPL.dat and how to
use them properly. I noticed a 4P 2Q test is not equivalent to a 2P 4Q,
generally speaking it does not commute. Why? What is clearly P and Q then:
P for number of processors per nodes and Q for the number of nodes?
Secondly, what is the definition of processor for a quad core
architecture? I suppose a quad core should be counted as 4 processors.
I launched Linpack using Ns=10000 and various configuration for P and Q.
At the moment I got a maximum of 78 Gflops using P=8 Q=4 -> 32 processors.
If I'm right the peak performance should be Rpeak= 4 cores x 4 floting
point op per cycle x 2.33 Ghz x 8 quad cores = 298 Gflops.
Which would lead to a test running at ~25% Rpeak.
This is very low and I see 3 causes for the problem:
- I miscalculated Rpeak
- P and Q are not set properly
- there is a serious bottelneck
Thanks for your advices
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