Restart file strategy

From: Robin Booth <>
Date: Wed, 1 Sep 2021 11:36:38 +0000

Hi Volker

I noticed that my Gadget4 run appeared to "stall" for several hours periodically during a run, with these instances roughly correlating to requested restart file outputs.
On further investigation, from inspection of the balance.txt file for example (see extract attached), it would appear that this is caused by the code performing a Nsync-grv on the entire particle set, including an expensive fof tree walk. This pushes up the CPU step time from typically 4 minutes to around 8 hours! Does that seem reasonable to you? I assume that this process is necessary for the restart files to record the particle parameters for all particles at the same timestep.
If this is indeed the correct restart file behaviour, then my conclusion would be that it is extremely counter-productive to request restart file output too frequently during a simulation run, particularly where I am running the simulation in time-limited "chunks". My understanding from the documentation is that a restart file will in any case be generated automatically when the run time approaches the limit set by the TimeLimitCPU parameter. Would you agree with this conclusion?



Received on 2021-09-01 13:36:53

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