[yt-users] basic question

[Elizabeth Tasker]

>> 
>> 
>> But basically, I can't create a function that I can plug into slice or projection without it running through the function a gazillion times?
> 
> You definitely can for slices.  If you define a derived field that is
> not ValidateSpatial, it will only be called once, on the slice.  The
> flow looks like this: inside get_data, for every field requested (in
> this case a derived field), it checks to see if it can generate that
> field.  If it can (i.e., it's not a grid-requiring or
> spatial-requiring field) it will do so.  If the field exists in the
> grid already, it will not be regenerated.
> 
> Unfortunately projections do require touching every grid.
> 

Hmm, OK I shall go away and think about this. Perhaps I could calculate my data set just once and then write a routine that simply checks which values are set on each grid, rather than perform the actual calculation....

Thanks!

Elizabeth