[yt-users] optimal resolution for frb

Nathan Goldbaum nathan12343 at gmail.com
Fri Sep 25 12:00:13 PDT 2015


Making it easy to lock the FRB resolution to the simulation resolution or
some factor-of-two multiple would be a great improvement, and something
that would be not too hard I think. Right now you're right that it's not
very obvious how to do this. If you'd be interested in coming up with a UI
for making FRBs that are locked to the simulation resolution, I think that
would be a fun first yt project that many people would like to use.

One easy way to get the size of the smallest computational element is the
`ds.index.get_smallest_dx()` function, which will return the size of the
smallest cell width in code units. The ds.index object is the main way to
access information about the geometrical or mesh properties of a dataset.

For patch AMR datasets like FLASH, you can access the grid objects like so:

for grid in ds.index.grids:
    print grid.LeftEdge, grid.RightEdge  # left and right edge of the grid
in code units
    print grid.ActiveDimensions  # the dimensions of the grid patch (i.e.
number of zones along x, y, and z)
    print grid.Level  # AMR leve
    print grid.Children  # references to child grid objects, if any
    print grid.Parent # reference to parent grid
    print grid['dens'] # the on-disk gas density field

You can access any yt field on the grid object using a dictionary-like
lookup, just like any other yt data object.

-Nathan

On Fri, Sep 25, 2015 at 1:18 PM, Slavin, Jonathan <jslavin at cfa.harvard.edu>
wrote:

> Hi all,
>
> I've been doing FLASH runs in 2D and using yt to manipulate the data for
> display -- that is, I've been creating frb objects from slices (which are
> not really slices since the data is 2D anyways).  One thing that bothers me
> about this is the need to specify the dimensions of the frb.  For some
> reason 800 x 800 seems to be preferred in the yt docs, but it seems to me
> that there are certain optimal dimensions that depend on the grid
> structure.  For example an frb that uses pixels the size of the smallest
> resolution element/cell or some integer multiple of that (of course less
> refined cells would be split into multiple pixels).  How would one find
> what that grid size would be?  I guess what I'd need to know is the
> dimensions of that most refined cell in the computational grid.  How does
> one access the grid structure information in a dataset?
>
> Jon
>
> --
> ________________________________________________________
> Jonathan D. Slavin                 Harvard-Smithsonian CfA
> jslavin at cfa.harvard.edu       60 Garden Street, MS 83
> phone: (617) 496-7981       Cambridge, MA 02138-1516
> cell: (781) 363-0035             USA
> ________________________________________________________
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