[mesa-users] critical problem with history interval

[Jakub Ostrowski]

Hi Lars,

My biggest issue is now the problem with MESA which I described and it basicaly doesn't have anything in common with WNJ.

The comparison is secondary thing. I pointed it out because I wanted to give you a reason why I've found this bug and I also think that this stage of evolution is a shortcoming of MESA. This is weird because it perfectly handles much more sophisticated stages.

Of course I can happily provide my settings of WNJ to anyone who is interested. Just tell me what you need and you'll have it. I'm definitely going to compare more tracks myself when the problem with MESA is gone.

And yes, you are right: WNJ doesn't have helium burning implemented so that the tracks I've shown you are everything you can get for massive stars. I cut calculations when central temperature rises to 10^8 K because higher values would be unrealistic due to the lack of support for next stages of nuclear burning.

Cheers,
Jakub


On 11 sty 2013, at 16:09, Lars Bildsten <bildsten at kitp.ucsb.edu> wrote:

> Jakub, 
> 
> It seems you are raising two distinct issues: 
> 
>     1. MS and just after MS, How does MESA compare to WNJ? For that exercise, it would seem to me that many on this mailing list 
>          can now make comparisons assuming you can let them know exactly all the settings in teh WNJ code. Such comparisons are 
>         extremely valuable and revealing, so I am eager to see how that works. 
> 
>     2. post MS and into the red. ..  It seems that WNJ does not proceed into that regime? If not, then look at the recent MESA Paper II where 
>           comparisons were made to STERN. If WNJ proceeds into that regime, let's make some comparisons with similar settings. 
> 
>   Thanks for your continued interest in using MESA! 
> 
>    Cheers
> 
> Lars
> 
> 
> On Jan 11, 2013, at 6:06 AM, Jakub Ostrowski wrote:
> 
>> Hi!
>> 
>> I'm reporting a critical problem that renders MESA pretty useless for me until I understand what's going on.
>> 
>> I observed that changing value of history_interval from 5 to 1 in 15 M_S model made enormous difference in evolution track which is rather ridiculous behavior. I can obtain one of two very different solutions just changing this one seemingly irrelevant parameter. 
>> <15m-hr.pdf>
>> Take a look at this HR diagram. Red line depicts the track I obtained with history_interval = 1 and green line is for history_interval = 5. I'll talk about blue line later on. Tracks are very different and the parameters of models are very different too. For example, model with logTeff ~ 4.20 that undergoes helium burning in the core and moves towards hotter temperature has for history_interval = 1 central abundance of he4 ~ 0.35 while model on similar place in HR but with history_interval = 5 has central abundance of he4 ~ 0.70. 
>> 
>> Which track is real? I have no idea. And take a look for similar figure calculated for 16 M_S models. The difference is even more obvious.
>> 
>> <16m-hr.pdf>
>> 
>> In order to solve a problem I have calculated 15 M_S model at least ten times, just changing history_interval. Generally speaking I always obtained one of these two solutions, but I ended with conclusion that it is even possible to obtain two solutions with history_interval = 1, but most likely there will look like in the first figure. This is even more problematic.
>> 
>> So my questions are: what's the reason for this behavior and how to fix it? And which (if any) solution is real?
>> 
>> There is also another problem that I would lie to point out. On both figures I plotted tracks from Warsaw - New Jersey code (blue lines). The main reason why I wanted history_interval = 1 was because of very poor reproduction of contraction after main sequence in MESA. Unfortunately even with every model in history file it looks like MESA loses some information - time step seems to be too long for this stage of evolution. There are only few points at this stage of evolution while Warsaw code beautifully renders this moment of star's life. I attached the files I used to plot these tracks.
>> 
>> Do you have any comments about that? Is it possible to get closer to solution of Warsaw - New Jersey code here?
>> 
>> All calculations have been carried out using MESA 4740 on OS X 10.8.2 with the latest SDK. I attached all inlists and obtained history files for every case shown on these plots.
>> 
>> I hope this is my simple failure and not a serious bug :)
>> Cheers,
>> Jakub
>> 
>> <report.zip>------------------------------------------------------------------------------
>> Master HTML5, CSS3, ASP.NET, MVC, AJAX, Knockout.js, Web API and
>> much more. Get web development skills now with LearnDevNow -
>> 350+ hours of step-by-step video tutorials by Microsoft MVPs and experts.
>> SALE $99.99 this month only -- learn more at:
>> http://p.sf.net/sfu/learnmore_122812_______________________________________________
>> mesa-users mailing list
>> mesa-users at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/mesa-users
>