[mesa-users] trace the computational cell that is limiting the timestep

[Bill Paxton]

Hi Mathieu,

1st, thanks for sending the inlist and a photo.  Usually it is better to send a saved model rather than a photo, but in this case it worked fine.

I made the following 3 changes in your inlist:

1)
use approx21.net instead of approx26.net

2)
      mesh_delta_coeff = 3
instead of
      mesh_delta_coeff = 1

for the late burning stages I've found that I can increase mesh_delta_coeff and still have enough cells.
in your case I'm still getting 1500+ cells even with mesh_delta_coeff = 3.
Try the larger value while you are trying to get things to work;
then come back and check for convergence by decreasing mesa_delta_coeff.

3)
         varcontrol_target = 1d-2
instead of
         varcontrol_target = 1d-4

again, like for mesh_delta_coeff, try a larger value while trying to get things to work.
then reduce it to check convergence later.

with these 3 changes, I was able to restart your photo and get it to go to core collapse in 247 steps in about 1.4 minutes of runtime.

       runtime, prev time, retries, backups, steps         1.4         2.0      9739       299    284247
     284247  10.126392   1848.395  23.430390  24.849838  12.308650   8.132779   0.000000   0.000000   0.327378   0.424153  10.954351   1538   9739
 -10.393057  10.622930   3.111692  21.739086  17.688434 -99.000000   4.175871   0.000010   0.000000   0.019025   0.350215   3.580514      3    299
 1.3391E+07  28.782825   4.244046  24.832632   1.198830  -9.604670   2.495086   0.000000   0.000000   0.000000  2.256E-01  0.000E+00  highT del Ye

Good luck!

-B








On Apr 13, 2014, at 7:46 AM, Mathieu wrote:

> Hi everyone,
> 
> I am wondering if there is a way to trace which computational cell is limiting the timestep in MESA 6208.
> 
> I am trying to simulate a 15 solar mass star with MESA 6208 and I find extremely small timesteps during Si shell burning.
> I know I could lower the min_timestep_limit (setting it to 10^-10 sec the run goes on), but I'd like to find why and where such small timesteps are needed.
> I attach the inlist I am using and a photo (284000), if someone wants to reproduce the problem.
> 
> Thanks for any suggestion,
> 
> Mathieu
> 
> 
> <284000><inlist_project.txt>------------------------------------------------------------------------------
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