Running the code

After building the code, an executable named athena will be created in the /build/src subdirectory. To run it, an input file must also be specified on the command line, e.g.

$ athena -i example.athinput

Examples of input files can be found in the /inputs subdirectory. Input files that work with the built-in test problems can be found in /inputs/tests.

When the code runs, all output files are created in the current working directory by default. The code will output simulation progress and some diagnosis messages to stdout.

Command-Line Options

A variety of command-line options have been implemented in AthenaK. The list of the options as well as the code configuration is given by the -h switch:

$ athena -h
Athena v0.1
Usage: athena [options] [block/par=value ...]
Options:
  -i <file>       specify input file [athinput]
  -r <file>       restart with this file
  -d <directory>  specify run dir [current dir]
  -n              parse input file and quit
  -c              show configuration and quit
  -m              output mesh structure and quit
  -t hh:mm:ss     wall time limit for final output
  -h              this help

Overriding Parameters in Input File

Some parameter values specified in the input file can be overridden by specifying new values on the command-line using the following format: <parameter_block>/<parameter>=<value>. For example, if you want to extend the simulation time limit when restarting,

$ athena -r example.00010.rst time/tlim=100

Some parameters, such as the sizes of the Mesh and MeshBlock, cannot be changed in this way.

Resuming Cluster Jobs from Latest Restart File

Large jobs on clusters often require submitting requests to continue from a checkpoint. The following snippet can help in making a submission script (e.g. for Slurm) that does this automatically. This uses $input_dir/$name.athinput but overrides the job/basename field to be $name. Only the # Parameters section needs to be modified from job to job, and generally at most the tlim entry needs to be modified with each restart. Additional command-line overrides can be specified with additional lines to the arguments variable.

# Parameters
name=<name of job and input file>
bin_name=<name of executable>
input_dir=<path to directory containing input file>
data_dir=<path to directory for writing outputs>
arguments="\
  time/tlim=<tlim> \
"

# Check for restart file
test_file=$(find $data_dir/rst -maxdepth 1 -name "$name.*.rst" -print -quit)
if [ -n "$test_file" ]; then
  restart_files=$(ls -t $data_dir/rst/$name.*.rst)
  restart_file=(${restart_files[0]})
  restart_line="-r $restart_file"
  printf "\nrestarting from $restart_file\n\n"
else
  restart_line="-i $input_dir/$name.athinput job/basename=$name"
  printf "\nstarting from beginning\n\n"
fi

# Run code
<srun or equivalent> <options> $bin_name -d $data_dir $restart_line $arguments