[MITgcm-support] speedup for cs64 on a linux cluster

[Angela Zalucha]

I also have not found any scaling analysis anywhere, but here is the test 
I performed:  I essentially run the 3D held-saurez cs experiment (with 
slightly more advanced RT) with 30 levels.  The test was performed on the 
Texas Advanced Computing Center Lonestar Linux cluster.  The test went for 
120,000 iterations.

I attached a plot.  The number of processors increases by powers of 2 
times 12 (i.e. 12, 24, 48, 96, 192, 384, 768, 1536).  I did not plot the 
ideal case but it would be a line.  The scaling is not ideal to large 
numbers of processors.  Oddly, the scaling is also not constant, e.g. 48 
to 96 and 192 to 384 produce a greater improvment than 96 to 192.

Also, I noticed for a given number of processors, lower nSx and nSy is 
always faster.

In 2D, on my group's local (Linux) cluster at Southwest, 2 procs is better 
than 1 proc, but 4 procs actually runs slower.

   Angela



On Tue, 22 May 2012, Maura BRUNETTI wrote:

> Dear MITgcm users,
> 
> I am studying scaling properties of ocean-only configurations on a linux cluster.
> The results shown in the attached figure are obtained with a cubed sphere configuration with 64x64 face resolution and 15
> vertical levels (points in the figure correspond to: 6 tiles 64x64 on 1 proc, 1 tile 64x64 on 6 procs, 1 tile 32x64 on 12
> procs, 1 tile 32x32 on 24 procs and 1 tile 16x32 on 48 procs). Only packages GMredi and tave are activated at run time.
> 
> The scaling is not very good, starting already at 12 procs (see blue line). I have not found in the literature other
> scaling analysis, could you please suggest where I can find them? From my analysis, I have seen that it is not worth
> doing runs with tile dimension smaller than 32 grid points. Is it correct?
> 
> Thanks,
> 
> Maura 
> 
> 
> --
> Dr. Maura Brunetti
> Institute for Environmental Sciences (ISE)
> University of Geneva -- Switzerland
> 
> 
>
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