Restarting

General

Cholla supports restarting a simulation from a checkpoint. Currently, hydro, MHD, dust, cosmology, scalars, and particles are all supported in restarts.

Cholla can read either concatenated or raw (un-concatenated) output files using either the Read_Grid_Cat or Read_Grid initial conditions function in the input parameter file. These functions can also be called using command line overriding with no change to the input parameter file. For example:

./bin/cholla input_file.txt  # original run
./bin/cholla input_file.txt init=Read_Grid indir=./dirname/ outdir=./dirname/ nfile=4  # restart

Read_Grid requires that the restart has the same number of processes as the original simulation.

Input data should be located in [indir], which should end with a slash (/) and may be a relative path. [outdir] is the directory where new data will be written. The files located in [indir] are expected to be named according to the following templates provided in the following table, where time = [nfile] * outstep and [rank] is the MPI rank ID.

data-type	Corresponding file-names	Other notes
hydro, mhd, dust, scalars	[nfile].h5.[rank]	Loading hydro is governed by Grid3D::Read_Grid() in src/io/io.cpp.
particles	[indir][nfile]_particles.h5.[rank]	Loading particles is governed by this section of code
gravity	[indir][nfile]_gravity.h5.[rank]

NOTE: Read_Grid_Cat restarts of simulations involving cosmology, gravity, or particles have not been rigorously tested