[MITgcm-support] Poor cpu usage percentage

[Rogan, Nicholas]

Hi Dimitris,
Thanks for getting back to me. Thanks for correcting me, I was under the impression that make -j 2 was to do with the runtime use of multiple cores. 

So, I have been running my MITgcm setup on my macbook pro for the last fw months. I had problems with my iMac and I could not ssh in to carry out the runs on there (It is currently sitting in a country other than the one I'm working). I was back visiting last week and got it up and running again. I am purely using it for running my model. 
For comparison:
My iMac is 2.66 GHz Intel core 2 duo with 8Gb RAM.
My macbook is 2.4 Ghz Intel core 2 duo with 4Gb RAM.

I compiled the MITgcm identically on both machines, but currently my Macbook is running about twice as fast as my iMac. The macbook usually has 5-10% IDLE CPU usage whereas the iMac is running with 65-90% IDLE CPU usage.They are both run with identical data files and the only program running on both (other than hidden processes) is Terminal. 

So I'm pretty sure the issue is not the I/O as I'm comparing relative to my macbook and I have no other programs running. I've attached screenshot of the top details. It's very strange, I've never had this problem before.

Nick






On 20/07/15 12:55 PM, Dimitris Menemenlis  <dmenemenlis at gmail.com> wrote:
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> Dear Nick, this does not answer you main question, but “make -j 2” only changes compilation time
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> by compiling using 2 parallel threads, the executable will not change.
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> Two wild guesses at what might be slowing down your code execution is if you have a lot of I/O
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> in your configuration, or maybe a lot of other programs running at the same time?
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> > On Jul 20, 2015, at 7:08 AM, Rogan, Nicholas <nrogan at geomar.de> wrote:
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> > I've tried building with "make" and also "make -j 2" (my iMac has a 2.66 GHz Intel core 2 duo with 8Gb RAM) but there was no discernible difference in the run speed.
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-- 
Kind regards,

Nick

------------------------------------------------------
Dr Nicholas Rogan
Postdoctoral Researcher
http://www.geomar.de/en/mitarbeiter/fb2/ch/nrogan/

GEOMAR Helmholtz Centre for Ocean Research, Kiel
Wischhofstraße 1-3, Build. 12
D-24148 Kiel
Germany
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