[yt-dev] Comment on YTEP-0028: No. of Base Units

[John Zuhone]

Hi Axel,

Just a quick question, are you all using mol and candela in your code? How do you envision the units representation in your files working with yt’s?

Best,

John
 
> On May 31, 2016, at 1:05 PM, Huebl, Axel <a.huebl at hzdr.de> wrote:
> 
> Hi John,
> 
> independent of the dev branch, I am really just referring to the written
> proposal in YTEP-0028 as of
>  https://ytep.readthedocs.io/en/latest/YTEPs/YTEP-0028.html <https://ytep.readthedocs.io/en/latest/YTEPs/YTEP-0028.html>
> .
> 
> I was just wondering since it is still "in progress" and we are
> implementing the openPMD description right now as a frontend which can
> express each quantity as a power to the seven SI base units in a generic
> fashion:
> 
>  https://git.io/vriio <https://git.io/vriio>
>  example: https://git.io/vrdpA <https://git.io/vrdpA>
> 
> Sounds great to extent the new UnitSystem a bit further to cover those.
> Allowing an additional measure for the angles is actually a nice thing -
> I like that, it's quite a common representation problem.
> 
> 
> Best,
> Axel
> 
> On 31.05.2016 15:36, John ZuHone wrote:
>> Hi Axel,
>> 
>> First, I presume you are referring to the new unit system functionality
>> in the development branch of yt, correct?
>> 
>> Currently in yt, "mol" is treated as "dimensionless" and we do not have
>> units of candela. I recognize this is different from the SI standard,
>> which has them as base units as you mentioned, and actually treats
>> angles as dimensionless.
>> 
>> There are a couple of things going on here:
>> 
>> 1. Angles are given a dimension since they have an important role in the
>> areas of science for which yt was originally tailored to, and it helps
>> things from a design perspective to distinguish them from dimensionless
>> units.
>> 
>> 2. The reason for the variance with the SI standard regarding mol and
>> candela is somewhat historical as well; yt originally worked only in CGS
>> units and even now assumes those as a default units base. The support
>> for different unit systems is new. The fact that we treat mol as
>> dimensionless and do not have candela is simply because a use case
>> requiring otherwise has not presented itself yet.
>> 
>> Do you have an application of yt that requires a closer adherence to the
>> SI standard? If so, we'd be willing to look into making some changes
>> along these lines.
>> 
>> Best,
>> 
>> John
>> 
>> 
>> ================================
>> John ZuHone, Chandra/ACIS Operations
>> Harvard-Smithsonian Center for Astrophysics
>> 
>> 60 Garden St. <x-apple-data-detectors://0 <x-apple-data-detectors://0>>, MS-67       (w) 617-496-1816
>> <tel:617-496-1816 <tel:617-496-1816>>
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>> <tel:781-708-5004 <tel:781-708-5004>>
>> 
>> john.zuhone at cfa.harvard.edu <mailto:john.zuhone at cfa.harvard.edu> <mailto:john.zuhone at cfa.harvard.edu <mailto:john.zuhone at cfa.harvard.edu>>
>> http://hea-www.cfa.harvard.edu/~jzuhone <http://hea-www.cfa.harvard.edu/~jzuhone>
>> ================================
>> 
>> On May 31, 2016, at 9:15 AM, Huebl, Axel <a.huebl at hzdr.de <mailto:a.huebl at hzdr.de>
>> <mailto:a.huebl at hzdr.de <mailto:a.huebl at hzdr.de>>> wrote:
>> 
>>> Dear yt-Developers,
>>> 
>>> we found today that the UnitSytem in YTEP-0028 has only 4 (MKS: 5) base
>>> units + the angular measure.
>>> 
>>> This is a bit confusing since the SI unit system has seven base units,
>>> further including mol (amount of substance) and candela (luminous
>>> intensity), which are not available.
>>> 
>>> Is this intentional?
>>> 
>>> 
>>> Best,
>>> Axel
>>> 
>>> -- 
>>> 
>>> Axel Huebl
>>> Phone +49 351 260 3582
>>> https://www.hzdr.de/crp
>>> Computational Radiation Physics
>>> Laser Particle Acceleration Division
>>> Helmholtz-Zentrum Dresden - Rossendorf e.V.
>>> 
>>> Bautzner Landstrasse 400, 01328 Dresden
>>> POB 510119, D-01314 Dresden
>>> Vorstand: Prof. Dr.Dr.h.c. R. Sauerbrey
>>>         Prof. Dr.Dr.h.c. P. Joehnk
>>> VR 1693 beim Amtsgericht Dresden
>>> 
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>> 
>> 
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> 
> -- 
> 
> Axel Huebl
> Phone +49 351 260 3582
> https://www.hzdr.de/crp <https://www.hzdr.de/crp>
> Computational Radiation Physics
> Laser Particle Acceleration Division
> Helmholtz-Zentrum Dresden - Rossendorf e.V.
> 
> Bautzner Landstrasse 400, 01328 Dresden
> POB 510119, D-01314 Dresden
> Vorstand: Prof. Dr.Dr.h.c. R. Sauerbrey
>          Prof. Dr.Dr.h.c. P. Joehnk
> VR 1693 beim Amtsgericht Dresden
> 
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