[yt-users] IsBound and mpi4py

[Stephen Skory]

Hi Eve,

> But is the derived quantity "IsBound" also not parallel in general? The code
> I'm using does not use clump object at all; all it's doing is picking out a
> sphere object centred around some point in the box

"IsBound" is precisely the expensive operation I mentioned in my last
email that is not parallel. That calls the functionality that
calculates the gravitational attraction between all cells in the
object and tells you if the object is bound or not. When someone is
sufficiently motivated, there are parallel treecodes that could be
included in yt, but that would be a significant project, and is not
likely to happen any time soon. Unless you want to volunteer! :)

> I thought the reason why clump finding does not work in parallel was because
> parallel contour algorithm was not yet implemented, which, if I understand
> correctly, is separate from "IsBound".

Yes, that is another reason why clump finding is not truly parallel.

The only way clump finding is parallelized now is over individual
clumps. That is, given a bunch of different objects, each object can
be processed by a single core, and therefore many are done at the same
time, but all the heavy lifting (IsBound) is done in serial.

-- 
Stephen Skory
s at skory.us
http://stephenskory.com/
510.621.3687 (google voice)