[Yt-dev] Parallel Hop

Matthew Turk matthewturk at gmail.com
Tue Feb 24 10:09:51 PST 2009


Anybody have any thoughts on this?  I'd like to wrap this up in the
next four days, if possible.

On Fri, Feb 20, 2009 at 5:49 PM, Matthew Turk <matthewturk at gmail.com> wrote:
> 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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>



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