Hi everyone,

I'm finally following up on this thread.  I just submitted a pull request for the docs that includes some documentation of how to create fields that use ghost zones.  Some of it was a little tricky to explain, so let me know if the wording can be improved.

Britton

On Wed, Jan 4, 2012 at 2:03 PM, Matthew Turk <matthewturk@gmail.com> wrote:
Hi Britton,

On Wed, Jan 4, 2012 at 1:32 PM, Britton Smith <brittonsmith@gmail.com> wrote:
> Hi Matt,
>
> I'm not sure I understand the change that you're talking about, but it seems
> that they were auto-detected in the past, since the example without them
> there used to work.  I'm in favor of returning to that if possible.
> Regardless, I think it would be worthwhile to add something to the derived
> fields documentation discussing this.  I could add that if we wanted it, but
> it will be good to have it reviewed, since I'm not very familiar with how it
> works.

I think the best solution would be to have it simply auto-detect the
fields necessary, rather than mandating they be specified (which may
not always give the correct results.)  I'll implement this tomorrow
morning.

After some digging, it seems to me that this situation arose because
we fixed a bug which had silently allowed this to occur, related to
checking for field parameters in fields requiring ghost zones.

-Matt

>
> Britton
>
>
> On Wed, Jan 4, 2012 at 1:26 PM, Matthew Turk <matthewturk@gmail.com> wrote:
>>
>> Hi Britton,
>>
>> It may not be documented, but I think we can actually auto-detect
>> them; this would add on a list of lists of strings to the hierarchy,
>> but I think that is manageable.  Would this be worthwhile?
>>
>> -Matt
>>
>> On Wed, Jan 4, 2012 at 1:24 PM, Britton Smith <brittonsmith@gmail.com>
>> wrote:
>> > Hi Sam,
>> >
>> > That fixed it, thanks!  I actually encountered this problem while
>> > working on
>> > my own derived field that used ghost zones and was using
>> > VorticitySquared as
>> > my example for how to do it.  I think in the past it was not required to
>> > list the fields with ValidateSpatial, which is why it was working as is
>> > in
>> > older versions.  I wasn't able to find documentation on how to make
>> > fields
>> > that use ghost_zones.  If it's in there and I just missed it, could
>> > someone
>> > point me toward it?  If not, I could add something to the Creating
>> > Derived
>> > Fields section.
>> >
>> > Britton
>> >
>> >
>> > On Wed, Jan 4, 2012 at 11:46 AM, Sam Skillman <samskillman@gmail.com>
>> > wrote:
>> >>
>> >> Hey Britton,
>> >>
>> >> It looks like VorticitySquared wasn't specifying the necessary fields
>> >> (x,y,z velocity) in the definition.  I will push a change momentarily
>> >> after
>> >> I look around at any other ghost zone requiring fields to make sure
>> >> they
>> >> work.  DivV, for example, does the right thing.
>> >>
>> >> Sam
>> >>
>> >>
>> >> On Wed, Jan 4, 2012 at 9:32 AM, Britton Smith <brittonsmith@gmail.com>
>> >> wrote:
>> >>>
>> >>> Hi everyone,
>> >>>
>> >>> I'm having a problem using fields that use ghost zones.  The following
>> >>> simple script:
>> >>> http://paste.yt-project.org/show/2010/
>> >>>
>> >>> gives this error:
>> >>> http://paste.yt-project.org/show/bOikDPScBBtDiUGvH11X/
>> >>>
>> >>> I am working from the tip, but I get the same behavior from yt/2.3.
>> >>> In
>> >>> yt/2.2, everything is working.  I am working now to narrow that range
>> >>> down a
>> >>> bit, but does anyone have an idea?
>> >>>
>> >>> Britton
>> >>>
>> >>> _______________________________________________
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>> >>
>> >>
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