Re: [mesa-users] minimum mass fraction values

[amber l. <amb...@gm...>]

Whenever I run with the adaptive net, the nets in the "nets" folder usually
have 70-100 species in my experience. I don't know if that's typical. I am
still doing XRB, as well as other models. Generally I run with Max Z, N,
and A turned off and use Min_X values ~10e-11. The 10e-21 run was for
benchmarking and to see if there was any significant difference, I had the
elapsed time column added but I didn't check it the total run time, but I
can if you are interested. It was really just a one off. The machine I'm
speaking of has 48Gb of memory and it can run that adaptive net case with
mesa_67.net as the initial net in a day. FWIW, my experience with MESA as
well as in other general computing is that increasing memory gives more
speedup than increasing cores.   There's probably documentation for this
effect, maybe someone more CS trained than I has a reference.

On Thu, Mar 9, 2017 at 2:30 PM, Robert Farmer <rjf...@as...> wrote:

> >So 17Gb is the max mesa can use for the nuc nets matrix solver?
>
> this is the combination of nuclear network plus structure equations (they
> are solved simultaneously) matrix,  you may use more memory overall as this
> doesn't include things like the eos files that are loaded etc
>
> Are you still doing xray bursts? what did you have for the other adaptive
> net options?
>
> Rob
>
> On Thu, Mar 9, 2017 at 1:21 PM, amber lauer <amb...@gm...> wrote:
>
>> So 17Gb is the max mesa can use for the nuc nets matrix solver? I just
>> finished a run with an adaptive net with my min Z set at 10e-21, and I used
>> a starting model with an abundance profile containing roughly 20 species. I
>> just checked the profile in the region of interest for my research, and
>> even with those settings the net only has about 70 species. So it works out
>> OK, at least in my case.
>>
>> On Wed, Mar 8, 2017 at 11:53 AM, Robert Farmer <rjf...@as...> wrote:
>>
>>> >Unfortunately in my case, this can be as low as 10e-9. For more final
>>> models, I have a machine built specially for this purpose with 16 cores, so
>>> I can dedicate a bit more time for the larger networks.
>>>
>>> There are limits on how big the matrix mesa can solve based on memory
>>> limits. Mesa memory scales as ~num_isos**2 * num_zones, with an upper limit
>>> based of the size of the 4-byte int used to index the matrix array (2^31-1
>>> which is about ~17GB of memory for double precision numbers). This is about
>>> 400 isos with 1000 zones, so if you want more isotopes you will need to
>>> reduce your spatial resolution.
>>>
>>> >What about when starting from an abundance profile? If I have an
>>> isotope with abundance of 10e-13, but min x for keep is set at 10e-9, for
>>> example, will it eliminate it immediately? Or after a few steps?
>>>
>>> Immediately, though it might get re-added if there is a reaction that
>>> makes it. This is the problem i find with the adaptive nets is once you add
>>> an isotope it gets quite hard to remove it, given all the possible
>>> reactions that could make it, so the nets never get smaller.
>>>
>>> Rob
>>>
>>>
>>>
>>> On Wed, Mar 8, 2017 at 10:18 AM, amber lauer <amb...@gm...>
>>> wrote:
>>>
>>>> Yeah, we've all experienced that vicious slowdown. However when trying
>>>> to match observables, you have to at least use the values from observation
>>>> as a lower bound. Unfortunately in my case, this can be as low as 10e-9.
>>>> For more final models, I have a machine built specially for this purpose
>>>> with 16 cores, so I can dedicate a bit more time for the larger networks.
>>>>
>>>> What about when starting from an abundance profile? If I have an
>>>> isotope with abundance of 10e-13, but min x for keep is set at 10e-9, for
>>>> example, will it eliminate it immediately? Or after a few steps?
>>>>
>>>> On Wed, Mar 8, 2017 at 10:33 AM, Robert Farmer <rjf...@as...>
>>>> wrote:
>>>>
>>>>> Hi
>>>>>
>>>>> Those values come from the cited Woosley, Heger, et al, ApJSS,
>>>>> 151:75-102, 2004 paper. I would advise against using them for mesa, in fact
>>>>> i'm going to go change them. If you look in the MESA3 paper at the x-ray
>>>>> burst section, I use much larger values for the different controls, 10**-6
>>>>> to 10**-3, the smaller the number for xmin the more isotopes you get in the
>>>>> net and you can very quickly get more than mesa can cope with.
>>>>>
>>>>> Rob
>>>>>
>>>>> On Wed, Mar 8, 2017 at 9:00 AM, amber lauer <amb...@gm...>
>>>>> wrote:
>>>>>
>>>>>> I'm trying to decide on a good min X, not just for the adaptive net,
>>>>>> but also for inclusion in abundance profiles. I see that the 'standard'
>>>>>> values in star_job.defaults are 10e-23 and ~10e-18. Is there a
>>>>>> numerical/computational argument for a relevant threshold?
>>>>>>
>>>>>> --
>>>>>> Amber Lauer. M.S. Physics
>>>>>> PhD Candidate,
>>>>>> Graduate School of Physics,
>>>>>> Louisiana State University
>>>>>>
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>>>>>>
>>>>>
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>>>>>
>>>>
>>>>
>>>> --
>>>> Amber Lauer. M.S. Physics
>>>> PhD Candidate,
>>>> Graduate School of Physics,
>>>> Louisiana State University
>>>>
>>>> ------------------------------------------------------------
>>>> ------------------
>>>> Announcing the Oxford Dictionaries API! The API offers world-renowned
>>>> dictionary content that is easy and intuitive to access. Sign up for an
>>>> account today to start using our lexical data to power your apps and
>>>> projects. Get started today and enter our developer competition.
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>>>>
>>>
>>
>>
>> --
>> Amber Lauer. M.S. Physics
>> PhD Candidate,
>> Graduate School of Physics,
>> Louisiana State University
>>
>
>


-- 
Amber Lauer. M.S. Physics
PhD Candidate,
Graduate School of Physics,
Louisiana State University