[Mesa-users] Questions about the debugging controls

[Rob Farmer]

grep -rinI 'log eps nuc ratio' star/p*/*
star/private/timestep.f90:1703:            if (s% report_all_dt_limits)
write(*,4) 'log eps nuc ratio', &

That leads to the function check_dlog_eps_nuc_change, note there are some
divide by eps_nuc's in there. So having 0's floating around (when you set
eps_nuc_factor to 0) is not going to help. I would suggest just using s%
dxdt_nuc_factor = 0d0  which turns off composition change from burning but
keeps eps_nuc set. That way your star won't just collapse as it runs out of
nuclear energy.

Try setting
report_solver_progress = .true.

and send the output for a step that seems to cause problems.

Rob



On Mon, 16 Aug 2021 at 20:31, Jeremy Sakstein <sakstein at hawaii.edu> wrote:

> Hi everyone,
>
> I've been having some convergence issues so I used the debugging controls:
>
> report_why_dt_limits
> report_all_dt_limits
> report_hydro_dt_info
>
> To try to figure out what is causing them. These helped a lot and I have
> been able to push the model much further but I am still unable to get full
> convergence so I wanted to ask a couple of questions.
>
> Currently, when I turn on report_why_dt_limits it just tells me
>
> "timestep_hold > model_number, so no timestep increase"
>
> If I also turn on report_all_dt_limits it tells me "log eps nuc ratio"
> followed by some ratios so I assume that eps_nuc is what is limiting the
> timestep? Is this the correct interpretation of this information?
>
> When I set
>
>    delta_log_eps_nuc_limit = -1
>    delta_log_eps_nuc_hard_limit = -1
>
> I still get this message, which confused me a bit because surely this
> means that eps_nuc should no longer limit the timestep?
>
> As an extreme test, I updated extras_start_step to set
>
> s% dxdt_nuc_factor = 0d0
>
> s% eps_nuc_factor = 0d0
>
> which I think should effectively turn off nuclear burning. Indeed, the
> abundances don't seem to change but I still get the same eps_nuc warning
> from report_all_dt_limits.
>
> Is someone able to tell me whether these changes are doing what I expected
> given my output?
>
> It would be great if someone could suggest either further ways I can
> determine what is limiting the timestep, or how to stop eps_nuc limiting
> the timestep if this is really what is happening.
>
> Cheers,
>
> Jeremy
>
>
>
>
> --
> Jeremy Sakstein (He/Him/His)
> Assistant Professor of Theoretical Physics
> Department of Physics & Astronomy
> University of Hawaiʻi at Mānoa
> Watanabe Hall
> 2505 Correa Road
> Honolulu, HI, 96822, USA
> http://www.jeremysakstein.com
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
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