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

[Sam Geen]

OK, will try to figure out all that tomorrow. I guess there's a guide to 
issuing pull requests on the yt site?

On 25/11/13 20:30, Matthew Turk wrote:
> Hi Sam,
>
> This looks great.  Any chance you could add this to the
> yt/frontends/ramses/definitions.py file as a function, issue a pull
> request, and we'll get your name in the commit log?  I'll then modify
> it to fit in and we'll use it as fallback when fields are specified.
>
> -Matt
>
> On Mon, Nov 25, 2013 at 1:39 PM, Sam Geen <samgeen at astro.ox.ac.uk> wrote:
>> 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> 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> 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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