[Yt-dev] Parallel Hop

[Matthew Turk]

Hi Stephen and others,

After my first email, I realized that we should not want the Domain to
be considered equal, but that I think we should not consider the dx's
to be different.  This breaks a bit of generalization, but I'm okay
with that.  Domains I think we should keep general.  I propose that we
accept a parameter:

minimum_halo_mass

which we can use to come up with padding by:

rho = total_mass / product(root_grid_dimensions)

this gives us a mass per root grid cell.  (Note that this is also the
mean dark matter density of the universe, if we only have DM
particles.  But HOP is more general than just DM, so we do not make
this assumption.)  We should have padding such that it's
over-resolving our minimum mass by some factor B.

padding = B * root_dx * minimum_halo_mass / rho

The reason I'm looking at this in terms of root grid cells is the
typical sync between root grid cells and the particles; Brian's done
some work with particle dimensions differing from the hydro dims, but
I think what we can consider is that even in that case, the two are
*correlated* by some multiple of RefineBy.  The same is true for
simulations with "zoom" particles.

Maybe I'm on the wrong track, but does this make sense to anyone else?
 Brian, Britton?

-Matt

On Fri, Feb 20, 2009 at 3:18 PM, Stephen Skory <stephenskory at yahoo.com> wrote:
>
>> I personally feel we should allow the user to specify the minimum
>> percentage of the matter enclosed in their box, and provide a
>> relatively low value for this.  From this, a length scale drops out,
>> based on the total number of particles and the domain size.  We cannot
>> assume that the domain runs from 0 to 1 or that the three axes are
>> identical.
>
> That's an OK solution for the dimensional problems you raise.
>
>  _______________________________________________________
> sskory at physics.ucsd.edu           o__  Stephen Skory
> http://physics.ucsd.edu/~sskory/ _.>/ _Graduate Student
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