[yt-users] wired square in enzo DM slice map

Junhwan Choi (최준환) choi.junhwan at gmail.com
Mon Jun 15 14:02:29 PDT 2015


Thank you Nathan,

As I mentioned in my original inquire, if I use other IC generator
such as CICASS, I do not get this wired square.
I found that the MUSIC generates ParticleDisplacements_x/y/z, while
the CICASS generates ParticlePositions for the DM particle position
information.
If this is the intrinsic enzo issue, there could be a subtle flaw for
the enzo's DM N-body calculation if one uses MUSIC output.
If this is a case, I had better report it to enzo user mailing list…

Best,
Junhwan


On Mon, Jun 15, 2015 at 1:20 PM, Nathan Goldbaum <nathan12343 at gmail.com> wrote:
> If this is a plot of the Enzo "Dark_Matter_Density" field that gets written
> to Enzo output files, then the artifacts you're seeing are generated by
> Enzo. yt is just plotting whatever is in your output files.
>
> You should be able to see how Enzo generates this field by grepping the
> codebase for "OutputSmoothedDarkMatter" and looking at the relevant code
> sections. One key thing: I believe Enzo's CIC deposit machinery doesn't
> handle grid boundary conditions properly, so and particles that should
> contribute to the cells that are at a grid boundary will only contribute if
> they are on one side of the grid boundary. This would lead to the deficits
> you're seeing. I haven't looked at that code in a while so please excuse me
> if I'm misremembering here.
>
> Hope that's helpful,
>
> Nathan
>
> On Mon, Jun 15, 2015 at 9:59 AM, Junhwan Choi (최준환) <choi.junhwan at gmail.com>
> wrote:
>>
>> Hi yt users,
>>
>> I have asked a similar question previously but I did get partial
>> answer so that I ask again.
>> I have made cosmological IC from MUSIC and run with enzo.
>> I made the DM density map with velocity arrow at z=200 which is
>> initial redshift using yt (and attach the figure).
>> It shows the wired square feature.
>> Previously, John wise suggested me to use enzo SPH smoothing to remove
>> this issue and it worked.
>> But, after test a few more run, I have couple more fundamental
>> questions on this issue.
>>
>> 1) Is this wired square effect is real effect in enzo or visualization in
>> yt?
>>     If this is an intrinsic enzo effect, we can say that DM gravity
>> calculation at high-z some kind of error.
>>     If this is an visualization effect, I found that other enzo
>> simulation using different IC generator does not show this effect (see
>> question 2).
>>     This difference makes me very confused.
>>
>> 2) I tested with other IC generator and I do not see the wired square
>> feature.
>>     I found that other IC generator output real DM position while
>> MUSIC IC generate displacement of DM particle position.
>>     Can it be the origin of issue?
>>
>>
>> I think this inquiry can go to enzo mailing list or MUSIC developer.
>> If it is necessary, I can ask it to other place.
>>
>> Thank you in advance,
>> Junhwan
>>
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>
>
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