[Users] strong scaling tests on Stampede (TACC)

[Bruno Giacomazzo]

Frank,

On Feb 21, 2013, at 8:05 PM, Frank Loeffler wrote:

> On Thu, Feb 21, 2013 at 06:31:23PM -0700, Bruno Giacomazzo wrote:
>> 	I found out that the problem is due to 1D ASCII output
>> 	(which is active in that parfile) and that makes the runs
>> 	particularly slow above ~100 cores on this machine.
> 
> That is not not just on this machine. xD output with x>=1 doesn't scale.
> Anywhere. Use HDF5, except for debugging where ASCII might be more
> convenient and you don't care about performance. There isn't much you
> could do about that without changing CarpetIOASCII.

	thank you for your comment. It's the first time that I see such a strong impact on runs using only ~100 cores. One of the reasons I did these tests was also that I was experiencing some problems with one of my production runs that was slower on Stampede than on Ranger.

>> 	and hence I didn't plot them in the other figure). I didn't try
>> 	using 1D hdf5 output instead, does anyone use it?
> 
> Not 1D, but 2D, and that works very well.


	I use 2D hdf5, but sometimes it's useful to have also 1D data (without having to postprocess 2D or 3D hdf5 files). I never used the 1D hdf5 output available in Carpet and I was wondering if other people use it.

Cheers,
Bruno

Dr. Bruno Giacomazzo
JILA - University of Colorado
440 UCB
Boulder, CO 80309
USA

Tel.  : +1 303-492-5170
Fax  : +1 303-492-5235
email : bruno.giacomazzo at jila.colorado.edu
web: http://www.brunogiacomazzo.org

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