[mesa-users] (no subject)

[Bill Paxton]

Hi Naveen,

On Dec 5, 2011, at 1:19 PM, naveen yadav wrote:

> Hi
> 
> 
> I am trying to run a model with low mass(0.5M_sun, 0.6M_sun).
> I am getting the output on terminal: 
> ...............................................................................................
>      dX_div_X too large for h1  917    0.5006254772E+00    0.5000000000E+00    0.7433708175E-02
>      dX_div_X too large for h1  897    0.5009315703E+00    0.5000000000E+00    0.7432030712E-02
>      dX_div_X too large for h1  898    0.5653517374E+00    0.5000000000E+00    0.7424575287E-02
>      dX_div_X too large for h1  900    0.5734262142E+00    0.5000000000E+00    0.7425290335E-02
>      dX_div_X too large for h1  898    0.5684504011E+00    0.5000000000E+00    0.7417244698E-02
>      dX_div_X too large for h1  905    0.5743475398E+00    0.5000000000E+00    0.7420076630E-02
> ...............................................................................................
> I find that the timestep.f has a parameter by this name. Can you please tell me  
> 1)what this parameter(dX_div_X) means ?


Sorry for the confusion --- I'll change the wording of that message for the next release to make it clearer.

As you discovered, it is giving you additional information about the timestep selection.   
Timesteps are limited to prevent too large change in mass fractions at any point.
The 1st line says that the relative change (dX_div_X) for mass fraction of h1 at cell 917 was too large
(the change was 0.5006254772 while the limit was 0.500000000), and this happened at mass coordinate 0.7433708175e-02.

So this isn't an error message -- it isn't even a warning.  it is just to give you some more information about the timestep selection.


> 2)Is there a description of these kind of control parameters somewhere in the code?


There are 3 kinds of controls for mesa/star -- they are defined in 3 files in the mesa/star/public directory.
The parameters for the "library" routines that do the work of evolving the model are in star_defaults.dek (&controls section of inlist)
The parameters for the "executive" routines are in run_star_defaults.dek (&star_job section of inlist)
And the parameters for the plotting routines are in pgstar_defaults.dek (&pgstar section of inlist)


Hope that helps.

Cheers,
Bill

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