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

[Matthew Turk]

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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>>>>>
>>>>>
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