Re: [mesa-users] minimum mass fraction values

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

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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>>
>>
>> --
>> 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
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>> http://sdm.link/oxford
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>>
>


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