[yt-users] strange particle field behavior

[Geoffrey So]

In my work with the secretive enzo-BW (~1.5) data, I've always just defined
my own derived field using creation time when I needed to check if a
particle is a star.  I don't recall using it in the ellipsoid parameter
find.  Not sure if Stephen used it in his halo finder, but I thought he
made his own as well.

a quick grep in the source show it being used only in:
frontends/enzo/fields.py:def _IsStarParticle(field, data):
frontends/enzo/fields.py:add_field('IsStarParticle',
function=_IsStarParticle,

But I don't know if others use this or not, and I don't know if I want to
use it in the future if I implement dm or dm+star in ellipsoid halo
calculations.  So I'm with Nathan that it's probably better to fix if it's
an easy fix.

From
G.S.


On Fri, May 10, 2013 at 2:17 PM, Nathan Goldbaum <nathan12343 at gmail.com>wrote:

> Hey Britton,
>
> I'd say -1
>
> In principle we should be able to define boolean fields.  If there's
> something about the way that handle fields that prevents that, we should
> fix it.
>
> -Nathan
>
> On May 10, 2013, at 2:13 PM, Britton Smith <brittonsmith at gmail.com> wrote:
>
> Ok, so we should probably remove that field from the code base since it is
> not really doing the right thing.  It doesn't seem to be in use anywhere.
> Does anyone have any thoughts on removing this? +-1?
>
>
> On Fri, May 10, 2013 at 4:49 PM, Matthew Turk <matthewturk at gmail.com>wrote:
>
>> On Fri, May 10, 2013 at 4:44 PM, Britton Smith <brittonsmith at gmail.com>
>> wrote:
>> > Hi all,
>> >
>> > I am seeing something odd with a field called "IsStarParticle".  This
>> is an
>> > Enzo field defined in the following way:
>> >
>> > def _IsStarParticle(field, data):
>> >     is_star = (data['creation_time'] > 0).astype('float64')
>> >     return is_star
>> >
>> > When I do the following:
>> > print pf.h.grids[0]['IsStarParticle']
>> >
>> > I get the expected field of 1s and 0s.
>> >
>> > When I do this:
>> > all_data = pf.h.all_data()
>> > print all_data['IsStarParticle']
>> >
>> > I get the values that correspond to the creation_time field.  It does
>> not
>> > matter in what order I do this.  Whenever I try to access the field
>> from a
>> > geometric object, I get the actual creation time and not the field I
>> expect.
>> > Whenever I access it from a grid object, I get the right thing.
>> >
>> > Does anyone know what's going on here?
>>
>> No, not really.  But there is one thing that I should note, which is
>> that it may be getting caused by using "IsStarParticle" as a boolean
>> index.  Which would not work correctly, and would just return the 0th
>> and 1st values of whatever array it's being used as an index into.  I
>> think.
>>
>> -Matt
>>
>> >
>> > Britton
>> >
>> > _______________________________________________
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