[yt-users] Cell Volume in regions

[Daniel]

Hi Desika,

If I read the log right the latest change is:

changeset:   12732:c9e843865b2a
branch:      yt
tag:         tip
parent:      12499:1b93a1840f38
user:        dcollins4096
date:        Sun Jul 06 20:08:39 2014 -0400

Thanks,
Daniel


On 10 July 2014 10:08, Desika Narayanan <dnarayan at haverford.edu> wrote:

> Hi Daniel,
>
> Which changeset are you on?  (Matt can correct me on this) but I think
> there was a time when the default was that over_refine_factor = 1.
>  Though that wouldn't explain equal cell and particle numbers...
>
> -d
>
>
> On Wed, Jul 9, 2014 at 3:29 PM, Daniel <cunnama at gmail.com> wrote:
>
>> I was comparing density and temperature to the cell_volume.
>>
>>
>> On 9 July 2014 20:04, Nathan Goldbaum <nathan12343 at gmail.com> wrote:
>>
>>> Which fields were you comparing with?
>>>
>>>
>>> On Wednesday, July 9, 2014, Daniel <cunnama at gmail.com> wrote:
>>>
>>>> Hi Matt,
>>>>
>>>> No, just loading a standard GadgetDataset:
>>>>
>>>> bbox = [[0.0, 1000000.0],
>>>>         [0.0, 1000000.0],
>>>>         [0.0, 1000000.0]]
>>>>
>>>> unit_base = {'UnitLength_in_cm'         : 3.08568e+21,
>>>>              'UnitMass_in_g'            :   1.989e+43,
>>>>              'UnitVelocity_in_cm_per_s' :      100000}
>>>>
>>>> pf = GadgetDataset("snapshot_050", unit_base = unit_base, bounding_box
>>>> = bbox)
>>>>
>>>> Cheers,
>>>> Daniel
>>>>
>>>>
>>>> On 9 July 2014 17:58, Matthew Turk <matthewturk at gmail.com> wrote:
>>>>
>>>>> Hi Daniel,
>>>>>
>>>>> On Wed, Jul 9, 2014 at 10:57 AM, Daniel <cunnama at gmail.com> wrote:
>>>>> > Hi Nathan,
>>>>> >
>>>>> > Thanks for getting back to me.
>>>>> >
>>>>> > That is odd, because then if my region includes all the particles I
>>>>> have
>>>>> > equal elements in cell_volume and all the other gas quantities?
>>>>> >
>>>>>
>>>>> Yup, that is a bit odd.  How are you loading the data?  Are you
>>>>> specifying either n_ref or over_refine_factor when doing so?
>>>>>
>>>>> -Matt
>>>>>
>>>>> > Kind Regards,
>>>>> > Daniel
>>>>> >
>>>>> >
>>>>> > On 9 July 2014 15:06, Nathan Goldbaum <nathan12343 at gmail.com> wrote:
>>>>> >>
>>>>> >> Hi Daniel,
>>>>> >>
>>>>> >> The cell_volume field is an alias for ('gas, 'cell_volume'), which
>>>>> for
>>>>> >> Gadget data corresponds to the volume of octree cells. In general
>>>>> there will
>>>>> >> be fewer octree cells than particles.  I'm a little surprised the
>>>>> numbers
>>>>> >> are so close since the default option is to refine octree cells
>>>>> when more
>>>>> >> than 64 particles are in a cell, although the precise structure of
>>>>> the
>>>>> >> octree will depend on the particle distribution.
>>>>> >>
>>>>> >> Nathan
>>>>> >>
>>>>> >>
>>>>> >> On Wednesday, July 9, 2014, Daniel <cunnama at gmail.com> wrote:
>>>>> >>>
>>>>> >>> Hi there,
>>>>> >>>
>>>>> >>> I am extracting a region from a Gadget dataset using the sphere
>>>>> function
>>>>> >>> and then attempting to access the "cell_volume" field.
>>>>> >>>
>>>>> >>> For some reason the number of elements in the cell volume field is
>>>>> not
>>>>> >>> equal to the number of particles in the region.
>>>>> >>>
>>>>> >>> For example I have 4341760 particles but only 4228930 cell volume
>>>>> >>> elements.
>>>>> >>>
>>>>> >>> I have extracted a sphere which encompassed all the particles and
>>>>> the
>>>>> >>> number of cell volume elements is then equal.
>>>>> >>>
>>>>> >>> Any ideas or advice would be greatly appreciated.
>>>>> >>>
>>>>> >>> Kind Regards,
>>>>> >>> Daniel
>>>>> >>
>>>>> >>
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>>>>> >
>>>>> >
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