[CP2K:637] Re: cp2k speedup on multicore machines

Teodoro Laino teodor... at gmail.com
Fri Jan 25 14:28:00 UTC 2008

The problem, unfortunately, is far being so obvious..

I think the MB is just mistyping.. (GB instead..)
And the problem is not only related to the benchmark input but also  
to small systems.
I suggested  Luigi to move to the benchmark test since in that case  
(a larger one)  you should definitely see scaling (more difficult
to observe with smaller systems). IO is reduced to the minimum in  
testing.. so don't consider the access to the disk.

Luigi, I just post the info you gave me about compilers/hardware.. I  
don't have the compilation flags.. Can you post them here in the group?

Linux k119 2.6.21-1.3194.fc7 #1 SMP Wed May 23 22:47:07 EDT 2007  
x86_64 x86_64 x86_64 GNU/Linux
gcc version 4.1.2 20070925 (Red Hat 4.1.2-27)
ifort Build 20070613 Package ID: l_fc_c_10.0.025
intel mkl

We use, on our local machines mostly the same setup.. The only  
difference is the kernel  (ours is a, could this be  
an issue Axel?) and the mpich2 (we use 1.0.5p4)...

Definitely it's not an OMP issue.. following Manuel suggestion I  
asked Luigi to set OMP_NUM_THREADS=1 and nothing changes in the  

Let's see if we can figure out what's going on..
Sure.. it's a little bit weird...

On 25 Jan 2008, at 15:06, Fawzi Mohamed wrote:

> well 8MB RAM is for sure a bottleneck ;)
> 8GB should not, but, well 6 Hours for 10 steps... maybe it did  
> swap, and if you swap then everything is over, do check, if memory  
> consumption is more than your physical memory the cpu usage drops  
> drastically, again in top you should see this.
> Use a smaller system, if this is the problem, the 32 water should  
> already scale well...

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