Setting initial conditions in restart files

PrincetonUniversity / athena

Athena++ radiation GRMHD code and adaptive mesh refinement (AMR) framework

https://www.athena-astro.app

BSD 3-Clause "New" or "Revised" License

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Setting initial conditions in restart files #615

Closed liangwang0734 closed 1 month ago

liangwang0734 commented 1 month ago

Hi Athena++ community, how I can set the state variable values in a restart file using an external data source (with B field also on Yee mesh)?

My case of application is not really external: We have an Athena++ simulation with 4x4x4=64 meshblocks per processor (after two uniform refinements) and found it seems to be scale worse than a simulation with the same global mesh size but only 1 large meshblock per processor. Thus we want to dump the data from the former simulation to a restart file compatible with the latter simulation.

msbc commented 1 month ago

What you want to do here is to make sure to dump out data in double precision (-h5double) and dump both the conservative variables (cons) and face centered B-fields (b). Then you basically just use the code from https://github.com/PrincetonUniversity/athena/blob/master/src/pgen/from_array.cpp in your pgen to read those hdf5 files and set the corresponding mesh block data.

liangwang0734 commented 1 month ago

Thank you @msbc , I will try that.

msbc commented 1 month ago

@liangwang0734 I just realized that I forgot to mention that the -h5double flag is a configuration time option, so you'll have to recompile your athena executable.