[Mesa-users] convergence problems in specific mass range

Tue Apr 9 06:23:50 EDT 2019

Hello Warrick,

First, thank you for help!
I am attaching some files to provide the missing context.

1. When the problems arises, the star is still in it's pre-main  
sequence phase, but beyond the phase in which it is exhibiting strong  
deuterium burning. The first retry comes at step 1741, when log_LH is  
still around -4. It is at the point of evolution in which the  
temperature starts to rise again (see tracks.png). The big points  
corresponds to step 1741 in all three evolutions, and they seem to  
correspond well to each other. Concerning profiles, the opacity  
profile looks exactly the same for all three masses at this step  
(opacities.png). The same holds for logT and logP (see logT.png and  
logP.png).

2. 'Working' means for me, that the evolution finished at the point  
where central hydrogen abundance reaches the value 0.66. The models  
with 0.54 and 0.56 solar masses reach this point after ~2380 steps.

Switching of convective premixing will of course make the evolution  
run much faster but it still shows the same convergence problems.  
Changing the net to basic.net resolves the problem, so the issue might  
be correlated to the net. Even if I run from step 1500 with a photo  
from the evolution with basic net, the problem doesn't arise. So  
something from the deuterium burning phase?

You are right, the inlist is kind of a mess. This has it's reasons,  
but i forgot to check it before sending this mail, I am sorry. I am  
resending a more tidy version of it.

Again, thank you for your help!

Zitat von Warrick Ball <W.H.Ball at bham.ac.uk>:

> Hi Thomas,
>
> I've started running your inlist but it's quite slow and it would  
> anyway be helpful if you could provide a lot more context.  For  
> example, you've said that MESA starts doing retries and backups "at  
> some point", which you've also mentioned is around model number  
> 1800.  But what point in the star's evolution is this? e.g. has it  
> started burning hydrogen yet?
>
> You've also mentioned that your inlist "works" (without having told  
> us in the email what it means to "work", though the inlist has a  
> stopping condition of X_c=0.66) for masses M/Msun = 0.54 or 0.56.   
> What's the difference between these three runs? i.e. if you compare  
> the histories of the three runs at M/Msun = 0.54, 0.55 and 0.56,  
> what changes?  What about profiles for each mass around model number  
> 1800?  And the corresponding age (or central hydrogen abundance)?
>
> Another typical thing to do is try switching off your non-default  
> options and build back up to the inlist that's not working the way  
> you expect. For example, I noticed you're using convective  
> premixing.  Have you tried switching that off?  What does that tell  
> you?
>
> These are just some ideas for the kinds of things you can look into  
> that will make it easier for someone (yourself included!) to  
> identify a solution to your problem.  It sounds like you've already  
> computed enough data to ask these more specific questions.
>
> It's also a good idea to clean up your inlists to only contain  
> values that have been changed from the defaults.*  It makes it  
> easier for others to identify potential issues and rules out some.   
> For example, you're using the non-default reaction network  
> (`pp_cno_extras_o18_ne22.net`).  Does the problem persist if you use  
> `basic.net`?  If so, you can just remove all of that from the inlist  
> (and it'll allow us to reproduce the problem faster).
>
> Cheers,
> Warrick
>
> * Similar advice is given at the beginning of the default  
> `star/work/inlist_project` file:
>
> ! For the sake of future readers of this file (yourself included),
> ! ONLY include the controls you are actually using.  DO NOT include
> ! all of the other controls that simply have their default values.
>
>
> ------------
> Warrick Ball
> Postdoc, School of Physics and Astronomy
> University of Birmingham, Edgbaston, Birmingham B15 2TT
> W.H.Ball at bham.ac.uk
> +44 (0)121 414 4552
>
>
> On Tue, 9 Apr 2019, Thomas.Steindl at student.uibk.ac.at wrote:
>
>> Hello everyone,
>>
>> I am running the same inlist for masses between 0.5 and 6 solar  
>> masses with steps of 0.05 solar masses. For some reason, the  
>> evolution of the 0.55 solar mass model stops after roughly 1800  
>> steps. All other masses work. If I change the mass to 0.54 solar  
>> masses, it works (same for 0.56). Therefore, there is something  
>> weird happening in the mass range around 0.55. I have been looking  
>> at the temperature, pressure, opacity and density profiles, yet I  
>> cannot find unexpected behavior.
>>
>> To clarify what happens: I am using MESA version r11532. At some  
>> point MESA starts doing retrys and backups until the timestep is to  
>> small. Taking a smaller limit for min_timestep_limit does not work  
>> - it will still stop. I have been checking the output of the newton  
>> solver - it takes up to 25 iterations at the end until giving up  
>> either because of average, max resid or tiny corrections.  
>> Additionally, using things like soften_grad_T do not improve the  
>> convergence substantially, the evolution just stops a few steps  
>> later.
>>
>> I am attaching the inlist. I would appreciate any help for  
>> resolving this problem. Thank you very much in advance.
>>
>> kind regards,
>> Thomas
>>
>

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