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

[Nathan Goldbaum]

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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>>>
>>
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