[Mesa-users] Technical issue: calculations going incredibly slow

Warrick Ball W.H.Ball at bham.ac.uk
Tue May 4 09:20:58 UTC 2021

Hi Amedeo,

I haven't tried your inlists (thanks for attaching them!) but a few more details would help.  What phase of evolution is the star in when it starts slowing down?  If you reboot and run `./rn`, does it always start slowing down at the same timestep?  Or is it always after about 10 minutes, and not necessarily at the same timestep?

I ask these questions because I have two ideas.  First, you might be filling enough RAM that the various microphysics tables start using the hard drive page file, which could be slow.  If this might be the case, try adding

     num_steps_for_garbage_collection = 1000 ! or something greater than default 0

to the `&star_job` part of your inlist.

My second (probably wrong) idea is that your CPU is overheating and the system is slowing it down.  I'm not sure about this because it isn't clear that rebooting would give it enough time to cool off.  There are many tools available but on Linux you can try [1]

     cat /sys/class/thermal/thermal_zone*/temp

for a quick look (output is in "millicelsius").  If this is getting to ~80-85°C, this might be your problem.


[1] https://askubuntu.com/questions/15832/how-do-i-get-the-cpu-temperature


Warrick Ball
Postdoc, School of Physics and Astronomy
University of Birmingham, Edgbaston, Birmingham B15 2TT
W.H.Ball at bham.ac.uk
+44 (0)121 414 4552

On Tue, 4 May 2021, mesa-users at lists.mesastar.org wrote:

> Hi all,
> here is my problem. I have set a pretty vanilla simulation on MESA (inlists attached), but because of some weird black magic my calculations go fast enough over the first ten minutes, and then they dramatically slow down. And I'm not talking about
> timesteps, but about the actual calculation time for each timestep.
> Even more weirdly, if I reset my PC and restart the simulations (./re) the code goes fast for another ~10 minutes and then slows again.
> I'm using Ubuntu 20.04, and I made sure no other process was running at the same time. And yes: I set the right number of cores.
> Did this happen to anyone else? Do you have any idea on how to solve this?
> Cheers,
> Amedeo

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