[yt-users] RAMSES units bug in yt-3.0

[Sam Geen]

OK, interesting. In theory RAMSES should have identical units for both 
particles and gas. I can hunt down a run with particles to test if you like.

Thanks!
Sam

On 09/05/14 17:22, Matthew Turk wrote:
> Hi Sam,
>
> On reflection, I think this might be related to getting the *particle*
> masses correct.  I will take a look at it as soon as I can.
>
> -Matt
>
> On Fri, May 9, 2014 at 11:00 AM, Sam Geen <samgeen at astro.ox.ac.uk> wrote:
>> Hmm, that looks like it should be "mass_unit = rho_u * length_unit**3" in
>> line 492. You're right that it mentions the boxlength issue, though.
>>
>>
>> On 09/05/14 16:50, Matthew Turk wrote:
>>> Hi Sam,
>>>
>>> Okay, sounds good.  Looking at how code unit attributes are set up:
>>>
>>>
>>> https://bitbucket.org/yt_analysis/yt/src/a14a150c7c81850df81346162bdaff271e77eb50/yt/frontends/ramses/data_structures.py?at=yt-3.0#cl-482
>>>
>>> suggests to me that length_unit takes into account boxlen, and
>>> mass_unit does not.  The comments have some indication why this might
>>> be.
>>>
>>> -Matt
>>>
>>> On Fri, May 9, 2014 at 10:46 AM, Sam Geen <samgeen at astro.ox.ac.uk> wrote:
>>>> Yep; both this and dd["density"] give cgs values that are too small by
>>>> roughly a factor of boxlen**3.
>>>>
>>>> One other thing I need to try is to make sure I'm using the very latest
>>>> version of YT; I've been playing around with the Ramses frontend so it's
>>>> possible my version is somehow out of sync. Will let you know if this
>>>> fixes
>>>> things.
>>>>
>>>>
>>>> On 09/05/14 16:42, Matthew Turk wrote:
>>>>> Hi Sam,
>>>>>
>>>>> Can you verify the units are in fact incorrect in *cgs*?  Something
>>>>> like this would work:
>>>>>
>>>>> ds = load(...)
>>>>> dd = ds.all_data()
>>>>> print dd.quantities.total_quantitiy("cell_mass").in_cgs()
>>>>>
>>>>> Your second message makes me wonder if there's just a slipup in how
>>>>> the units are returned.
>>>>>
>>>>> -Matt
>>>>>
>>>>> On Fri, May 9, 2014 at 10:37 AM, Sam Geen <samgeen at astro.ox.ac.uk>
>>>>> wrote:
>>>>>> Sorry for the spam; a second bug I've seen is that the density and
>>>>>> pressure
>>>>>> unit labels on figures appears to be broken; it seems to print a
>>>>>> latex-mangled code names for the units rather than the cgs name of the
>>>>>> units; see attached example. Temperature is fine.
>>>>>>
>>>>>>
>>>>>> On 09/05/14 16:28, Sam Geen wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> Just to say that in the latest version of yt-3.0 (i.e. since various
>>>>>>> fields were renamed or re-implemented), I've found a bug in the
>>>>>>> implementation of "cell_mass", which is giving results that are too
>>>>>>> low
>>>>>>> in
>>>>>>> my runs; I believe the issue is that it's missing a factor of
>>>>>>> pf["boxlen"]**3 (which is of course only a problem if boxlen is not
>>>>>>> 1).
>>>>>>> The
>>>>>>> previous "CellMass_Msun" worked fine. If I get time I might take a
>>>>>>> look
>>>>>>> and
>>>>>>> issue a pull request, but otherwise I'm just flagging this in case
>>>>>>> someone
>>>>>>> else runs into problems; you can just manually multiply the result by
>>>>>>> pf["boxlen"]**3 until it's fixed.
>>>>>>>
>>>>>>> Cheers,
>>>>>>>
>>>>>>> Sam
>>>>>>> _______________________________________________
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>>>>>>> yt-users at lists.spacepope.org
>>>>>>> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>>>>>>
>>>>>>
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