[Mesa-users] dt_limit: max increase and decrease

Jacqueline Goldstein jgoldstein at astro.wisc.edu
Fri Feb 2 07:14:07 EST 2018

I am running the simplex module in MESA r10081 and see dt_limit outputs  ‘max increase’ and ‘max decrease’ but don’t understand what these are.

I see the output is set here
star/private/star_private_def.f90:         dt_why_str(Tlim_max_timestep_factor) = 'max increase’
star/private/star_private_def.f90:         dt_why_str(Tlim_min_timestep_factor) = ‘min increase’

And that the timestep factor is defined here
star/public/star_def.inc:      integer, parameter :: Tlim_max_timestep_factor = Tlim_struc + 1
star/public/star_def.inc:      integer, parameter :: Tlim_min_timestep_factor = Tlim_max_timestep_factor + 1

where Tlim_struc is defined
star/public/star_def.inc:      integer, parameter :: Tlim_struc = 1

and set to ‘varcontrol’ here
star/private/star_private_def.f90:         dt_why_str(Tlim_struc) = ‘varcontrol'

Conceptually I understand that Varcontrol limits how much a variable is allowed to change between steps, but can someone help me follow that up the chain to understand what max increase and min increase are?

Thank you,

Jacqueline Goldstein
PhD Graduate Student | Astronomy
University of Wisconsin - Madison

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