[Yt-dev] covering grids

[Matthew Turk]

Sorry, the bzr repo is at:

http://bzr.enzotools.org/yt/integer_cgrid/

On Thu, Feb 12, 2009 at 3:45 PM, Matthew Turk <matthewturk at gmail.com> wrote:
> Hey guys,
>
> I have implemented the integer-based covering grid.  It's not really
> much faster; the interpolated one should be, but the primary one is
> not.  (This was disappointing to me.)
>
> Anyway, this exposed a slight bug in the covering grid generation of
> ghost zones.  I have attached an example plot.  Upper left is the new,
> upper right is the old, lower left is the relative difference.
> abs(new-old)/(new+old).
>
> It looks to me like an off-by-one in the grid values.  This should not
> change substantially any of the calculations, as it still gives
> *correct* values, so contouring and whatnot should still work exactly
> correctly.  We just get a little bit of bonus data one one side and a
> little less on the other.  It's *possible* that if your contour join
> was exclusively in the ghost zone of a single grid that you now have
> too many; this seems kind of unlikely to me, but it still should be
> addressed.  I'm going to fix it, but probably by inserting the new
> routine rather than by fixing the old one.  The only thing remaining
> (you can see for yourself at my bzr repo:
> http://bzr.enzotools.org/integer_cgrid/ ) thing to do is to do
> periodic domains and smoothing.  For smoothing I will be implementing
> the (int math friendly) algorithm from Ralf Kaehler.
>
> -Matt
>