[Mesa-users] STELLA Errors and Number of Frequency Bins

Sun May 17 11:09:16 EDT 2020

Hi Jake,

Just a reminder from the relevant discussion in the MESA4 instrument paper.   See the last paragraph in section 6.4.  Here are the important parts for the topic of your concern:
Our emphasis is on bolometric luminosities, where 40 STELLA frequency bins are adequate. However, broadband light curves are also reported by STELLA. Figure 35 shows how the STELLA colors change as one goes from 40 to 200 frequency bins in a model approximately matching the bolometric luminosity of SN 1999em (99em_19 in Table 3). This reflects the fact that a given band is spanned by only a small number of frequency bins. The non-public research version of STELLA can opt to use many more frequency bins to address under-resolution issues. There are no current plans to include that capability in MESA.

The version of STELLA included in the mesa distribution is great for bolometric luminosities, and that’s what we intended as it’s use.  We show color light curves in MESA4 because those are important, and approximate results are possible with the STELLA version in MESA.  But that doesn’t mean you can hope/expect to get high quality color light curves with this tool.  If you need that, then you need to use a tool that is appropriate for that purpose.  You might contact the STELLA group about perhaps using their more advanced versions.  Or see about using SEDONA.   Or ….

If you can get value out of using the MESA version of STELLA in ways that don’t break it, that’s wonderful.  If it breaks when you push it, then back up a bit until it works again.  That may mean sticking to 100 bins instead of 200 if you find that sometimes things fail with the larger number.   If you are afraid the color lightcurve results are not converged then don’t use them. 

Happy computing,
-Bill

> On May 17, 2020, at 7:50 AM, Jake Nicoll via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Jared,
> 
> Thank you for looking into this. I will continue to run with as many frequency bins as I can.
> 
> I attached a comparison of the UVBRI quasi-bolometric light curves from the mesa.lbol files corresponding to runs with various frequencies. Ignoring the fact that I have not achieved a perfect fit or extended the light curves past the default 170 days yet, you can observe that the light curves seem to be "converging" as the number of frequency bins increases. However, there is some significant oscillation of the tails as one increases from 40 to 60 to 80 bins, and this oscillation makes the dependence of the light curve on the number of frequency bins unclear. It makes me wonder a little whether jumping to, say, 200 frequency bins would significantly impact the light curve. Just food for thought.
> 
> Thanks again,
> -Jake
> 
> From: Jared Goldberg <goldberg at physics.ucsb.edu <mailto:goldberg at physics.ucsb.edu>>
> Sent: Friday, May 15, 2020 4:39 PM
> To: Jake Nicoll <jwnicoll at outlook.com <mailto:jwnicoll at outlook.com>>
> Cc: mesa-users at lists.mesastar.org <mailto:mesa-users at lists.mesastar.org> <mesa-users at lists.mesastar.org <mailto:mesa-users at lists.mesastar.org>>
> Subject: Re: [Mesa-users] STELLA Errors and Number of Frequency Bins
>  
> Hi Jake, 
> I am running STELLA in the 12778 version of MESA with the mesa.abn and mesa.hyd files created using the example_make_pre_ccsn and example_ccsn_IIP test suite cases (with certain parameters adjusted for specific cases). I am trying to use more frequency bins to better fit individual U, B, V, R, and I color curves to observational data. However, I sometimes encounter errors which disappear when using fewer bins.
> For example, I successfully ran STELLA with the attached mesa.hyd and the mesa.abn files with 400 spatial zones and 120 frequency bins. However, when I tried to use 150 frequency bins, I received the error: "0Matrix is numerically singular-decomposition aborted", and STELLA failed to run.
> 
> I have seen the error myself, and can reproduce it with your input files. I also ran your mesa.hyd and mesa.abn files on 2 different computer architectures. On my Arch linux desktop I found the same singular matrix message you did, whereas on my mac laptop the calculation ran to ~160 days with 150 frequency bins, but crashed with a "file already open" warning (memory-related) without generating any mesa.lbol or useful output. We suspect a possible memory leak, such as in the opacity table calculations, which is being looked into further. Moreover, the numbers of grid points (for the opacity tables) and frequency bins are somehow capped for computational reasons, and these limits are hard-coded into the version of STELLA that ships with MESA. Thus for the memory issue with finer frequency binning, unfortunately there is simply an upper limit on the number of bins you can use. My solution has been "run with 100-120 bins and see if the results you care about are converged" and the occasional corollary "don't trust the colors much if they're not converged." 
>  
> I am wondering if someone can help me understand these errors and let me know if there is a way to work around them that does not involve using fewer frequency bins. 
> I have also received error messages which read "Segmentation fault, invalid memory reference" for other sets of .abn and .hyd files.  I am not sure if these error messages are related, but I have worked around both of them by reducing the number of frequency bins I run with.
> 
> I believe the issues are related, and again are likely related to these memory limitations and the calculation of the opacity tables.  The "invalid memory reference" segfault, in fact, occurred for me after the opacity table calculation as STELLA started its hydrodynamical when I tried to run these same .abn/.hyd files with 200 frequency bins. Unfortunately, the best work-around is to use fewer frequency bins, and check convergence. (Say, run with 100, 120, and 130 bins, and see how different the colors look).
> 
> Cheers, 
> ~Jared 
>  
> 
> On Fri, May 8, 2020 at 1:19 PM Jake Nicoll via Mesa-users <mesa-users at lists.mesastar.org <mailto:mesa-users at lists.mesastar.org>> wrote:
> Hi all,
> 
> I am running STELLA in the 12778 version of MESA with the mesa.abn and mesa.hyd files created using the example_make_pre_ccsn and example_ccsn_IIP test suite cases (with certain parameters adjusted for specific cases). I am trying to use more frequency bins to better fit individual U, B, V, R, and I color curves to observational data. However, I sometimes encounter errors which disappear when using fewer bins.
> 
> For example, I successfully ran STELLA with the attached mesa.hyd and the mesa.abn files with 400 spatial zones and 120 frequency bins. However, when I tried to use 150 frequency bins, I received the error: "0Matrix is numerically singular-decomposition aborted", and STELLA failed to run.
> 
> I have also received error messages which read "Segmentation fault, invalid memory reference" for other sets of .abn and .hyd files. I am not sure if these error messages are related, but I have worked around both of them by reducing the number of frequency bins I run with.
> 
> I am wondering if someone can help me understand these errors and let me know if there is a way to work around them that does not involve using fewer frequency bins.
> 
> Best,
> -Jake Nicoll
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