[yt-users] Bad grid edges in particle fields

[Matthew Turk]

Hi Casey,

There's not yet a FAQ on this -- feel free to add it to the yt FAQ or
to the Enzo docs under the FAQ section, and it'll geti ncluded in the
respective rebuilds.

A few months ago someone claimed to me that they had solved this
problem in Enzo with a one or two line modification to the IO
routines, by adding a boundary exchange just before output.  This fix
was never described or passed along.  For the purposes of yt I think
we can address it more directly by allowing a buffer zone when
calculating CIC_Deposit and including particles in the manner similar
to the fix you showed in the other thread.

-Matt

On Tue, Feb 28, 2012 at 10:14 AM, Casey W. Stark <caseywstark at gmail.com> wrote:
> Thanks Matt.
>
> Good to know that it is Enzo and not a bug either. Is there a FAQ on issues
> like this anywhere? It would be very helpful for new users and I would be
> happy to document this one.
>
> Best,
> Casey
>
>
> On Tuesday, February 28, 2012, Matthew Turk wrote:
>>
>> Hi Casey,
>>
>> On Mon, Feb 27, 2012 at 11:45 PM, Casey W. Stark <caseywstark at gmail.com>
>> wrote:
>> > Hi all.
>> >
>> > This is a projection of the Dark_Matter_Density field from the initial
>> > output of a standard enzo cosmological run with just 2 cores. It looks
>> > like
>> > something is going wrong on the grid boundaries. This occurs for
>> > projections
>> > and slices, but only for gridded particle data. The gas density looks
>> > fine.
>> > It seems to occur at every grid boundary, which I tested by increasing
>> > the
>> > number of cores (so the same number of grids).
>>
>> This is "real" in the sense that what you're seeing *is* in the data,
>> but in fact is not a problem in the simulation.  The grid edges show
>> up because particles *should* but *cannot* be interpolated across
>> these boundaries during yt, and in Enzo to get them to be interpolated
>> at the output time an exchange of boundary conditions has to occur.
>> Adding this to Enzo shouldn't be hard; adding it to yt might be
>> possible if you extend your other patch to work with smoothed covering
>> grids and validate spatial of at least one or two zones.
>>
>> -Matt
>>
>> >
>> > I can't tell if this is an enzo or yt issue, but I figured I should ask
>> > here
>> > first in case I missed something on the yt side. Has anyone seen this
>> > before?
>> >
>> > Best,
>> > Casey
>> >
>> > P.S. What is the status of the yt image server? Should we attach or
>> > imgur
>> > images in the future?
>> >
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