On Tue, Oct 29, 2013 at 9:32 AM, Cody Permann <codyperm...@gmail.com> wrote:
>
> On Tue, Oct 29, 2013 at 5:54 AM, ernestol <ernes...@lncc.br> wrote:
>
> > I am using an cluster with 23 node for a total of 184 cores, and each
> node
> > additionally has 16GB of RAM. I was thinking that the problem maybe is in
> > the code. Because if I run at up to 3 processors I dont have any problens
> > but when I try with 4 or more I get this problem.
>
So you have 8 cores per node, and 2 GB of RAM per core, which is pretty
standard.
I ran your 200^3 code on my Mac workstation and watched the memory usage in
Activity Monitor.
The results were somewhat surprising as I added cores:
1 core: 2.22 Gb/core
2 cores: 4.0 Gb/core
3 cores: slightly more than 4.0 Gb/core
4 cores: machine went into swap (I think) after approaching about 3.5
Gb/core but code eventually finished
5 cores: machine again went into swap at around 3.3 Gb/core but finished
eventually
My workstation has 20 Gb of RAM, so including the OS I guess I could see
how approaching 16Gb might cause it to go into swap.
But, what is happening when we go from 1 to 2 cores that causes the memory
usage per core to double?!
Note that in all cases the memory quickly jumps to about 2.22 Gb core. In
the 1 processor case it stays there, but in the 2-5 processor cases, after
reaching 2Gb/core, it slowly ramps up to the approximately 4 Gb/core listed
above.
This, combined with the error message you received (which comes from Metis)
leads me to believe that the partitioner is taking up a ton of memory
(partitioner doesn't run on 1 proc). So the questions become:
1.) Is the partitioner taking up a lot more memory than it conceivably
should? (Seems like yes.)
2.) Is it taking up more than it used to? I.e., has a bug been introduced
recently (Metis and Parmetis were last updated in April 2013, so pretty
recently actually)
I don't know about reverting to a prior version of Metis/Parmetis is easily
done at this point, but the relevant hashes where the refresh happened seem
to be:
e80824e86a
1c4b6a0d12
I may take a stab at this after lunch... Cody has been seeing similar
issues recently as well.
--
John
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