​Hi Nathan, Thanks very much for the detailed response. I had no idea that ds.index contains so much information. I've looked at the grid data for a simulation I did and it's quite revealing. Unfortunately for my case, a 2D simulation, it seems that ds.index.get_smallest​_dx() includes the third (unused) dimension, which for some reason is given a (very small) thickness in FLASH data. As a result, I get that very small dimension from ds.index.get_smallest_dx(). Nevertheless, it seems that it should possible to get the smallest grid dimension in each direction via the use of ds.index.grids.RightEdge and ds.index.grids.LeftEdge. I'm working on it now. ​Regards, Jon​ On Sat, Sep 26, 2015 at 11:25 AM, <yt-users-request@lists.spacepope.org> wrote:

Date: Fri, 25 Sep 2015 14:00:13 -0500 From: Nathan Goldbaum <nathan12343@gmail.com> To: Discussion of the yt analysis package <yt-users@lists.spacepope.org> Subject: Re: [yt-users] optimal resolution for frb Message-ID: <CAJXewO= 1rW7E+VkFeVqogWV+8Uq_Tq_rkufLDZ3xaA8tWuQzWg@mail.gmail.com> Content-Type: text/plain; charset="utf-8"

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

-- ________________________________________________________ Jonathan D. Slavin Harvard-Smithsonian CfA jslavin@cfa.harvard.edu 60 Garden Street, MS 83 phone: (617) 496-7981 Cambridge, MA 02138-1516 cell: (781) 363-0035 USA ________________________________________________________