[mesa-users] "failed to find all required l=0 modes"

[Richard Townsend]

Hi Warrick —

This is interesting; when running the example in star/astero/work, I find lots of similar occurrences of “failed to find all required l=0 modes”. I’m not sure whether these existed in older MESA versions; I’ll check. If not, then it looks like we have a regression which needs tracking down.

cheers,

Rich

> On Nov 11, 2014, at 1:28 AM, Warrick Ball <wball at astro.physik.uni-goettingen.de> wrote:
> 
> Hi,
> 
> In short, I was wrong about how to fix this issue.  If get_radial is set to .true., then the code thinks that chi^2 is small enough that it's worth evaluating the non-radial modes, which isn't the case.
> 
> So, for now, I'm just sidestepping the issue by cranking up the limit on the number of "bad" models.  When I have some time, I'll have another go at trying to understand how things should be restructured to make more sense.
> 
> But my previous "fix" is no fix!
> 
> Cheers,
> Warrick
> 
> On Fri, 7 Nov 2014, Warrick Ball wrote:
> 
>> Hi,
>> 
>> I was looking at the results of a recent asteroseismic fitting run using ersion 7184, and found errors of the form
>> 
>> "failed to find all required l=0 modes"
>> 
>> after nearly every chi^2 evaluation in the range where only the radial modes are considered.  This came as a surprise, since the code was returning a useful value of  chi^2.
>> 
>> I grepped the error message and identified it's source at line 375 of star/astero/src/extras_support.f.  The message is displayed when the function get_radial returns a false.  I then had a look at get_radial (line 631).
>> 
>>   if (chi2_radial > chi2_radial_limit .and. nl1 + nl2 + nl3 > 0) then
>>      write(*,'(a50,i6,99f16.2)') &
>>         'chi2_radial > chi2_radial_limit', &
>>             s% model_number, chi2_radial, chi2_radial_limit
>>      return
>>   end if
>>   get_radial = .true.
>> 
>> I might be misinterpreting the code, but it looks to me like this will leave get_radial as false if chi2_radial > chi2_radial_limit, and thus the error will be printed.  But the error message doesn't correspond to what's actually happened.  That is, the modes have all been found, but the current value of chi^2 is too large for it to be worth continuing to evaluate the higher-degree modes.
>> 
>> If I'm right, then the fix is simply to put get_radial = .true. before the last if block.  But, as always, I might be wrong...
>> 
>> Cheers,
>> Warrick
>> 
>> 
>> 
>> ------------
>> Warrick Ball
>> Postdoc, Institut für Astrophysik Göttingen
>> wball at astro.physik.uni-goettingen.de
>> +49 (0) 551 39 5069
> 
> 
> ------------
> Warrick Ball
> Postdoc, Institut für Astrophysik Göttingen
> wball at astro.physik.uni-goettingen.de
> +49 (0) 551 39 5069------------------------------------------------------------------------------
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