[yt-users] RFC: RAMSES field aliases in yt-3.0

Sam Geen samgeen at astro.ox.ac.uk
Mon Nov 25 10:39:32 PST 2013


I've hacked up a simple example of what I mean (attached).

On 25/11/13 17:50, Nathan Goldbaum wrote:
> Matt's opened a PR for this here:
>
> https://bitbucket.org/yt_analysis/yt-3.0/pull-request/140/adding-field_aliases-to-ramses-datasets/diff 
>
>
> Sam, if you could enumerate how to map from the boolean flags you're 
> suggesting to a final field list, I think that would help immensely.
>
>
> On Mon, Nov 25, 2013 at 8:42 AM, Sam Geen <samgeen at astro.ox.ac.uk 
> <mailto:samgeen at astro.ox.ac.uk>> wrote:
>
>     Yes and no. NVAR must be big enough, but it can be bigger than
>     necessary (I think); it's a Makefile setting when compiling
>     Ramses. You can guarantee that the first 4 variables are the same,
>     but after that I suspect the best approach is to use boolean flags
>     to specify whether the run contains MHD, RHD, metals, etc.
>     Normally it's a good guess that 5 is pressure and 6 (if it exists)
>     is metals, but as I said it seems like MHD puts the B-field before
>     pressure and metallicity.
>
>
>     On 25/11/13 17:36, Nathan Goldbaum wrote:
>>     Does that mean that it should be possible to infer the field list
>>     from NVAR alone?
>>
>>
>>     On Mon, Nov 25, 2013 at 8:29 AM, Sam Geen <samgeen at astro.ox.ac.uk
>>     <mailto:samgeen at astro.ox.ac.uk>> wrote:
>>
>>         For MHD, the variables stored are the B-field strengths on
>>         the faces of each cell - the fields in order are: (1)
>>         density, (2-4) [x,y,z] velocity, (5-7) [x,y,z] B-field left,
>>         (8-10) [x,y,z] B-field right, (11) pressure (thermal + MHD),
>>         then (12+) any passive scalars (metals, etc) - see
>>         mhd/output_hydro.f90. Note that the MHD module adds 3
>>         variables, so the number of variables will be nvar+3.
>>
>>         For RHD (Joki Rosdahl's M1 method implementation, at least -
>>         someone else will have to help with the ATON version), there
>>         is a separate "rt_" output file for each CPU (like the
>>         hydro/amr/particles), as well as a separate info file (there
>>         is a bitbucket link on the Ramses homepage if you want to see
>>         what the latest version of the code does in detail). The RHD
>>         module divides photons into "nGroups" different flux bins;
>>         for each bin, it writes a photon density and then a flux
>>         vector. nGroups is stored in the rt info file; nrtvar is
>>         written to the rt_ binary file, but this is (I think) a
>>         Makefile setting and not guaranteed to be nGroups/(1+ndim)
>>         (the user is, I believe, normally free to waste memory by
>>         allocating more variables than they need). For details it
>>         might be easiest to download the latest code and look at the
>>         code in the folder rt/, or ask Romain or Joki Rosdahl directly.
>>
>>         (Feel free to correct me if any of this is wrong!)
>>
>>         I agree that setting the default to the standard five
>>         (perhaps some boolean variables for common configurations
>>         such as metals, RHD, MHD, etc) and then letting users set or
>>         add their own fields by hand if they need to is a good approach.
>>
>>
>>         On 25/11/13 16:23, Matthew Turk wrote:
>>
>>             Hi all, especially RAMSES users,
>>
>>             I'm setting up aliases to make it easier to load RAMSES
>>             datasets that
>>             have different field configurations.
>>
>>             Right now, to specify a different set of fields, you have
>>             to do:
>>
>>             pf = load( ... , fields = [ "Density", "x-velocity", ...])
>>
>>             I am going to change this to add on different field
>>             configurations
>>             that can be specified with just a string.  For instance:
>>
>>             pf = load(..., fields = "standard_five")
>>
>>             I'm wondering what the different configurations are.  I
>>             have these two:
>>
>>             standard_five: Density, x-velocity, y-velocity,
>>             z-velocity, Pressure
>>             standard_six: Density, x-velocity, y-velocity,
>>             z-velocity, Pressure, Metallicity
>>
>>             But for MHD and RHD, what are the additional fields that
>>             should be
>>             added, and in what order?  And are there other common
>>             configurations
>>             that should be aliased?
>>
>>             If we can come up with a set of aliases that match most
>>             use cases,
>>             that'd work quite well.  I'm going to issue a PR for this
>>             shortly, and
>>             hopefully it will make everybody's life a bit easier.
>>
>>             -Matt
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