mesa-users] Using Mesa

[Bill Paxton]

On Nov 10, 2008, at 5:09 AM, Roni Waldman wrote:

> I am interested in trying out mesa,

> Where is the actual evolution code, and how do I run it?


Hi Roni,

I'm happy that you're interested in trying out mesa.   The top-level  
stellar evolution package is "mesa/star".

Like the other packages, mesa/star is organized with sources in  
public and private directories.  In mesa/star/public you'll find  
procedures (in star_lib.f), stellar data (in star_data.dek), and  
control parameters (in star_controls.dek).  Code that actually runs  
the mesa/star evolution package can be found in mesa/star/test/src.   
However, you shouldn't have to edit those files (at least not for  
now).  Instead, the parameters of a run are read from a text file  
called 'inlist' that lives in the star/test directory.  You can edit  
that file to pick things such as initial_mass and initial_Z as well  
as more exotic things like which nuclear net to use.

After you've set up inlist, you can launch the code by using one of  
several little script files that are found in star/test:

./rn
  -- run an evolution using the current contents of inlist.

Information about the state of the star is periodically written to  
the terminal (at a frequency determined by the 'log_cnt' control).

The code also periodically saves "snapshots" of the internal state  
for possible restarts (the 'photostep' control determines how often  
this happens).  For model numbers that are a multiple of 1000, the  
name of the snapshot is simply the model number.  Otherwise, the name  
is 'x' followed by the last 3 digits of the model number. For  
example, a snapshot of model 1325 will be saved as x325.  The  
snapshot files are saved in the 'photos' directory.  (This naming  
scheme was created after I filled up my disc with snapshots during an  
overnight run -- now with photostep set to 10 or 20, I can let it run  
overnight without worrying about creating too many snapshots.)

If you want to change some controls and restart from the snapshot in  
x325, do

./re x325
   -- restart using snapshot in file photos/x325

Logs and profiles are written to the 'LOGS' directory in test  
(profiles are saved at a frequency determined by the  
'profile_interval' control; a star log entry is created for each model).

The files 'log1.data', 'log2.data', etc. have information about a  
particular model.
The file 'profiles.index' has information about what's in those log  
files.
Finally, 'star.log' has the history for the entire run of a variety  
of values.

The LOGS information is automatically reset when you start a new  
evolution using ./rn, but it is not reset when you do a restart  
using ./re -- however it is okay to delete the entire contents of  
LOGS at any time during a run; it will automatically remake the files  
and keep going from there.

You'll find that the profiles and logs are organized as columns of  
data with enough text info included to make it reasonably clear  
what's what.

I use Tioga for plotting (it was created for this sort of thing), and  
the plot routines that I use for mesa/star can be found in  
star_history and star_profile.

At this time, the documentation for mesa/star is limited to emails  
from me!    So don't hesitate to ask.  Just understand that things  
are still in a very preliminary state; I'm sure there are lots of  
bugs out there waiting to be found.  ; - )

Cheers,
Bill

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