[Mesa-users] What is a dt error and how to fix it?

[Rob Farmer]

Hi,
>terminated evolution: cannot find acceptable model

This is telling you that mesa is struggling to find a valid solution.
Sometimes lowering min_timestep_limit helps to get through a hard phase,
but in this case at 10^-15 s you're at a very small timestep so the model
isn't going to go anywhere. You should also look at the terminal output to
see what is limiting MESA's timestep.

Have you looked at some plots to see what MESA is doing at this point in
time? That is the first place to look to see what MESA is doing and if it
is doing something sensible.

>redo with smaller timestep to get closer to stopping target
log_center_temperature >= log_center_temp_limit    0.9534297744E+01
 0.7600000000E+01

I'm not sure why you have in your inlist_to_lgT9.9: log_center_temp_limit =
7.60d0  considering this inlist is is meant to be for Si burning and beyond
(and in fact your model has a lgT at the center of 9.53 and is starting at
a core temperature of lgT=9.3). I expect this is causing some issues,
perhaps try altering this to match what the filename of the inlist suggests:

log_center_temp_limit = 9.90d0

it should be doing

Rob


On Sat, 20 Jun 2020 at 09:18, Pieter de Klerk via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi all,
>
> I am using MESA r12778, MESA SDK x86_64-linux-20.3.2, and my OS is Linux.
>
> So, I am trying to run a 22Msun model from the pre-main sequence to the
> core-collapse stages but a dt error keeps on popping up whenever MESA reads
> an inlist file (inlist_to_lgT_9.9 in this case):
>
> redo with smaller timestep to get closer to stopping target
> log_center_temperature >= log_center_temp_limit    0.9534297744E+01
>  0.7600000000E+01
>                                                               .
>                                                               .
>                                                               .
>
>  retry     951
>                                                      dt
>  7.6255263322678794D-15
>                                      min_timestep_limit
>  7.6499999999999993D-15
>
>  stopping because of problems dt < min_timestep_limit
>
>
> terminated evolution: cannot find acceptable model
>
> termination code: min_timestep_limit
>
> I am new to MESA and would like to know what a dt err is, how to fix this
> error, and how it can be avoided.
>
> It says "redo with smaller timestep to get closer to stopping target..."
> so I decreased the order of magnitude of min_timestep_limit but that did
> not help.
>
> Is there something I should add or remove in this model?
>
> The error pops up on photo x950.
>
> I attached a folder containing the inlist files.
>
>  22M model+.zip
> <https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F1gQlKaTY50hhf1seVveCLhX6IXBek3HAw%2Fview%3Fusp%3Ddrive_web&data=02%7C01%7Cr.j.farmer%40uva.nl%7C667831f6c19b4c4b2f7608d8154550b2%7Ca0f1cacd618c4403b94576fb3d6874e5%7C1%7C0%7C637282734742536599&sdata=XKWRfkuomR%2BzMK%2Fy2%2Bh9Ct2NJsqJ9E6Cha8wXjqFmqk%3D&reserved=0>
> Kind regards,
> Pieter.
>
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