renv changes an environment variable according to the MPI rank / task ID of the process as a prefix to your application.

Say goodbye to your complicated Bash wrapper scripts!

Just insert renv in the command line before your application, giving the environment variable to change as the single, first argument. Similar to env or xenv:

srun -n 2 renv MYVAR ./myapp -a 1

This will set MYVAR to 0 for task 0 and 1 for task 1.

The program can be installed through pip:

python3 -m pip install git+https://github.com/FZJ-JSC/renv

• -h: Print help
• -g, --global: Use global task IDs and not node-local task IDs (i.e. SLURM_PROCID instead of SLURM_LOCALID)
• -f, --force: Allow overwrite a pre-existing environment variable
• -m, --map: Don't simply set the task ID to the environment variable, but first replace it according to a map; i.e. --map '0: 2' would set the environment variable for task 0 to 2, and not to 0
• --separator-map, --separator-keyval: Change the separator for parsing the map and the key-val-pairs, respectively. Default are , for entries in the map and : to separate keys and values. Use RENV_SEPARATOR_MAP and RENV_SEPARATOR_KEYVAL to override the behavior globally (the command line option takes precedence, though).

Right now, only Slurm is supported; but other schedulers are prepared. Please file an issue.

• Simple usage:

  $ srun -n 2 renv ABC env | grep ABC
  ABC=1
  ABC=2

• Set environment variable CUDA_VISIBLE_DEVICES to 3 for rank 0 and 2 for rank 1:

  $ srun -n 2 renv --map '0:3,1:2' CUDA_VISIBLE_DEVICES env | grep CUDA_VISIBLE_DEVICES

• Combine both examples by stacking renv:

  $ srun -n 1 renv ABC renv --map '0:2,1:2' CUDA_VISIBLE_DEVICES env | grep "CUDA_VISIBLE_DEVICES\|ABC"

• Combine with env:

  $ srun -n 1 env ABC=DEF CUDA_VISIBLE_DEVICES=0 renv --map '1:3,2:2' CUDA_VISIBLE_DEVICES env | grep "CUDA_VISIBLE_DEVICES\|ABC"