[yt-dev] ipython-physics

[Britton Smith]

+1 for Sympy + Dimensionful.

On Tue, Oct 23, 2012 at 11:57 AM, Anthony Scopatz <scopatz at gmail.com> wrote:

> I am +1 for adding sympy.
>
>
> On Tue, Oct 23, 2012 at 9:55 AM, Matthew Turk <matthewturk at gmail.com>wrote:
>
>> Hi all,
>>
>> Sorry for letting this drop.
>>
>> My feeling is that we should definitely go with dimensionful (Casey's
>> project), and add SymPy to the stack.  It seems likely that the
>> emerging SciPy stack will include SymPy as a component, and
>> furthermore it's pure python, so it should not be terribly difficult
>> to include in that respect.
>>
>> Having a coherent unit stack is crucial.  Right now we have the
>> really, really terrible (and I take full blame for this) overloading
>> of parameter files like dictionaries.  As an example, here's how Enzo
>> would work:
>>
>> pf["time"]
>> pf["InitialTime"]
>> pf["kpc"]
>> pf["HydroMethod"]
>> pf["seconds"]
>> pf["Density"]
>>
>> All of these do different things.  And, on the backend, they query
>> different dictionaries -- units, conversion_factors, and parameters.
>> This is not okay!  We have:
>>
>> pf.current_time
>>
>> but this is given in code units for some reason for most codes.
>>
>> I think we should move to a system where when querying, the person
>> doing the querying needs to explicitly state what they want.  And all
>> the unit conversion stuff (time, length, fluid, etc) needs to be
>> handled by a separate process -- and my preference would be that it
>> would be handled by dimensionful.  I think that can come in at a
>> higher level than the conversion from on-disk to CGS, but it should
>> come in somewhere.
>>
>> I would absolutely love to rip out all of the dictionary-access for
>> parameters this instant -- moving to tuples of (value, unit) was the
>> first step, to get away from value/pf[unit].  But we can't do this
>> just yet, and it needs to happen at a 3.0 break.
>>
>> What does everyone think?  Can we do a [+-][01] on SymPy +
>> Dimensionful, or do we need more info?
>>
>> -Matt
>>
>> On Sat, Oct 6, 2012 at 12:59 AM, Anthony Scopatz <scopatz at gmail.com>
>> wrote:
>> > Hi Mike,
>> >
>> > ipython-physics looks like a good, relatively simple solution.  I would
>> > assume that we would use this *instead* of sympy to prevent having to
>> add
>> > yet-another-dependency and end up packaging this right with yt.  (ip-p
>> seems
>> > to be unlicensed yet 'placed in the public domain', which is weird
>> since the
>> > public domain is not a legal construct everywhere.  We would need to ask
>> > them about that before including in yt.)
>> >
>> > That said, I think a sympy solution would end up being more powerful
>> > ultimately.  Additionally, ip-p definitely needs some clean up before
>> > inclusion.  At quick glance they seems to use camel case for some
>> functions,
>> > their main class NumberDict subclasses from dict (huge no-no,
>> > collections.MutableMapping people!), all of the _addUnit() calls at the
>> end
>> > of the file should be hard coded into _unit_table (or a mapped call),
>> they
>> > seem to be definitely using eval() wrong by not having an empty globals
>> dict
>> > which captures builtins, and the unit comments never seem to be used
>> (so why
>> > have them?).  And they have no tests!
>> >
>> > So I would be in favor a rewrite of ip-p, but sympy would be better ;)
>> >
>> > Be Well
>> > Anthony
>> >
>> > On Fri, Oct 5, 2012 at 7:24 PM, Michael Kuhlen <mqk at astro.berkeley.edu>
>> > wrote:
>> >>
>> >> Hi yt gang
>> >>
>> >> Just had a little chat with Matt, and he suggested I bring up
>> >> ipython-physics for discussion. Sounds like unit handling is an issue
>> that
>> >> needs to be addressed in yt. I've found ipython-physics to be pretty
>> neat
>> >> and quite usable. Maybe this is something worth tying into yt? Matt
>> also
>> >> mentioned that Casey had written a sympy-based library for handling
>> units;
>> >> how does it compare to what ipython-physics does?
>> >>
>> >> Mike
>> >>
>> >> --
>> >> *********************************************************************
>> >> *                                                                   *
>> >> *  Dr. Michael Kuhlen              Theoretical Astrophysics Center  *
>> >> *  email: mqk at astro.berkeley.edu   UC Berkeley                      *
>> >> *  cell phone: (831) 588-1468      B-116 Hearst Field Annex # 3411  *
>> >> *  skype username: mikekuhlen      Berkeley, CA 94720               *
>> >> *                                                                   *
>> >> *********************************************************************
>> >>
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>> >
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