[yt-dev] Projection wipes grids

[Elizabeth Tasker]

Hi Matt,

OK! I'll add a warning comment to my own program and we'll all live in hope I read my own notes, or at least google the mailing list before asking you the same question in 6 months time ;-)


Elizabeth


On 2012-07-04, at 7:53 PM, Matthew Turk wrote:

> Hi Elizabeth,
> 
> This is probably due to the projection scripts calling either
> preload() for the data fields, or calling clear_data() on the grids.
> 
> Right now unless we can track down where those calls are made, and
> come up with a way to temporarily disable them, I think your best bet
> is avoiding projecting.  The longer term solution, which could be
> useful for other applications as well, is a data sidecar file -- so
> you could save a field generated in memory to disk.  I don't know when
> I will be able to work on that, but perhaps someone else here will
> have some ideas.
> 
> -Matt
> 
> On Wed, Jul 4, 2012 at 4:37 AM, Elizabeth Tasker
> <tasker at astro1.sci.hokudai.ac.jp> wrote:
>> Hi,
>> 
>> I'm using a code which creates a new field by assigning values to
>> individual cells.
>> 
>> If --in the middle of the script-- I create a projected image, the new
>> field gets wiped.
>> 
>> This script demonstrates the problem:
>> 
>> http://paste.yt-project.org/show/2517/
>> 
>> Here, the code loops over two objects, and gives their neighbouring
>> cells values in the new field and creates an extracted region from
>> those cells.
>> 
>> When the second object is called, the code reassigns its cells to
>> object one and creates a new extracted region of object one's cells.
>> 
>> If line 53 is not called (p = pc.add_projection("Density", 2)), this
>> is fine. Both objects initially have 26 cells and then object one gets
>> 52 cells.
>> 
>> If the projection is created, the code forgets about the cells it
>> assigned to object 1 in the first loop and object 1 ends up with only
>> object 2's cells.
>> 
>> 
>> This isn't a huge problem for me, since I can just ensure I never call
>> a projection during my script.
>> 
>> But.... I am liable to forget and clobber my data at a later point! Is
>> it easy to somehow bank the new field so it's not destroyed during a
>> projection? (If not, no worries.)
>> 
>> (Matt, I know we previously discussed how projection didn't know about
>> the new field. Possibly, this is a logical consequence from that and
>> if so, I'm sorry to repeat the question!)
>> 
>> Elizabeth
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