Run WarpX

In order to run a new simulation:

  1. create a new directory, where the simulation will be run

  2. make sure the WarpX executable is either copied into this directory or in your PATH environment variable

  3. add an inputs file and on HPC systems a submission script to the directory

  4. run

1. Run Directory

On Linux/macOS, this is as easy as this

mkdir -p <run_directory>

Where <run_directory> by the actual path to the run directory.

2. Executable

If you installed warpX with a package manager, a warpx-prefixed executable will be available as a regular system command to you. Depending on the choosen build options, the name is suffixed with more details. Try it like this:

warpx<TAB>

Hitting the <TAB> key will suggest available WarpX executables as found in your PATH environment variable.

Note

WarpX needs separate binaries to run in dimensionality of 1D, 2D, 3D, and RZ. We encode the supported dimensionality in the binary file name.

If you compiled the code yourself, the WarpX executable is stored in the source folder under build/bin. We also create a symbolic link that is just called warpx that points to the last executable you built, which can be copied, too. Copy the executable to this directory:

cp build/bin/<warpx_executable> <run_directory>/

where <warpx_executable> should be replaced by the actual name of the executable (see above) and <run_directory> by the actual path to the run directory.

3. Inputs

Add an input file in the directory (see examples and parameters). This file contains the numerical and physical parameters that define the situation to be simulated.

On HPC systems, also copy and adjust a submission script that allocated computing nodes for you. Please reach out to us if you need help setting up a template that runs with ideal performance.

4. Run

Run the executable, e.g. with MPI:

cd <run_directory>

# run with an inputs file:
mpirun -np <n_ranks> ./warpx <input_file>

or

# run with a PICMI input script:
mpirun -np <n_ranks> python <python_script>

Here, <n_ranks> is the number of MPI ranks used, and <input_file> is the name of the input file (<python_script> is the name of the PICMI script). Note that the actual executable might have a longer name, depending on build options.

We used the copied executable in the current directory (./); if you installed with a package manager, skip the ./ because WarpX is in your PATH.

On an HPC system, you would instead submit the job script at this point, e.g. sbatch <submission_script> (SLURM on Cori/NERSC) or bsub <submission_script> (LSF on Summit/OLCF).

Tip

In the next sections, we will explain parameters of the <input_file>. You can overwrite all parameters inside this file also from the command line, e.g.:

mpirun -np 4 ./warpx <input_file> max_step=10 warpx.numprocs=1 2 2