[Yt-dev] Parallel Hop
Stephen Skory
stephenskory at yahoo.com
Thu Jan 22 17:26:35 PST 2009
All,
> Could you quantify that a bit, Stephen? I definitely agree with the
> point about the fuzziness of halo boundaries, but how far off are the
> results when you vary processor count? If you were to make halo
> catalogs of the same dataset using 1,2,4,8, etc. processors, and then
> compare them (assuming that n=1 processor is the "perfect" solution),
> how far off are the halo centers?
If you're interested, I've made a parameter-space survey of processor counts and padding, here, with lots of pictures:
http://stephenskory.com/research/?p=1469
It's password protected. Contact me off-list if you want it.
But in summary, I found that parallel hop differs from serial by no more than 1% in absolute particle count, and the change is larger in smaller haloes, which are already vague to begin with. Even for very large objects (relative to the box) a little bit of padding goes a long way, 0.05 is nearly identical to a padding of 0.2. However, padding is still required to get good answers. The centers change by very, very little between serial and parallel.
_______________________________________________________
sskory at physics.ucsd.edu o__ Stephen Skory
http://physics.ucsd.edu/~sskory/ _.>/ _Graduate Student
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