[yt-dev] "faking" away variable-by-level refinement

Chris Malone chris.m.malone at gmail.com
Thu May 23 12:10:30 PDT 2013


Casey - Ok good, I didn't know there was anyone else who had used that
feature.  One issue with a script to alter the dataset by adding levels is
that I think BoxLib likes --- but perhaps doesn't _enforce_ --- there to be
some padding between levels so that a coarse level isn't entirely covered
by fine data.  Again, this could be remedied by interpolation, but I don't
really care about the data on this intermediate level.  The approach within
yt would be nice because it could simply ignore the data, possibly.

Matt -

> > So, for the time being, I want to move forward with testing out the
> > consolidated BoxLib frontend on a real dataset.  I could, of course,
> write a
> > script offline that would take my old datafile, create intermediate-level
> > grids and populate the data by averaging or interpolating the real data
> so
> > that all levels have the same refinement ratio, but I've just "faked" the
> > data for the levels that I have added.
>
> Ah, wow!  And have the tests worked so far?
>

This was something that I could do, but have not yet.  I apologize if that
was misleading!


> I have thought about this, and I believe it's quite reasonable.  For
> what it's worth, we do something slightly similar with the RAMSES
> frontend, in that we have a min_level that we assume it refines to.
> (Not completely the same thing, but similar idea.)  There is a
> mechanism for creating a fake grid, which is to set up a covering
> grid, but that assumes the existence of a hierarchy already.  But it
> might also be possible to fake the grid itself during the creation of
> the hierarchy (setting a flag on it or something) and doubling up the
> data.
>

Ok, so there is some fake grid precedent.  I'll look at the Ramses code to
get a feel for what is happening there.  If we don't actually care about
the data on the fake grid, does it even need to be doubled?  It surely
doesn't need to be a deep copy, but does data actually need to exist within
the hierarchy at a specific level, or would that cause problems?

Chris
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