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Reference

Configuration

csauto reads its configuration from a TOML file and environment variables.

Config file lookup order

csauto finds csauto.toml in this order (first match wins):

1. --config /path/to/csauto.toml (CLI flag)
2. CSAUTO_CONFIG environment variable
3. ./csauto.toml (current working directory)
4. <repo_root>/csauto.toml (repository root, i.e. parent of the csauto/ package)

If no file is found, all default values are used.

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Complete annotated configurations

Local workstation (native)

Code
# Use the code_saturne binary installed on the machine
runtime = "native"
solver_bin = "/opt/code_saturne/bin/code_saturne"

# No Slurm; csauto run launches at most 2 cases at a time
use_slurm = false
max_parallel = 2

# Web UI: accessible only from this machine
host = "127.0.0.1"
port = 8000

HPC cluster with Slurm

Code
# Native code_saturne on the compute nodes
runtime = "native"
solver_bin = "/opt/code_saturne/bin/code_saturne"

# Submit each case as a Slurm job
use_slurm = true

# MPI options injected via CS_MPIEXEC_OPTIONS for each sbatch job
mpi_exec_options = "--mca btl vader,self,tcp --bind-to core"

# csauto run keeps at most 20 jobs submitted (queued or running) at a time
max_parallel = 20

# Serve UI on login node, tunnel with: ssh -L 8000:127.0.0.1:8000 login-node
host = "127.0.0.1"
port = 8000

Singularity / Apptainer container

Code
runtime = "singularity"
singularity_image = "/opt/images/code_saturne.sif"
singularity_bin = "/usr/bin/apptainer"   # optional: auto-detected if in PATH

use_slurm = false
max_parallel = 2

host = "127.0.0.1"
port = 8000

For code_saturne with use_slurm = true, csauto submits a dedicated batch script for the Singularity runtime (.csauto.slurm.sh in the case folder). The job follows the same pattern as a manual HPC launch: code_saturne run --stage --initialize, then srun ./cs_solver --mpi, then code_saturne run --finalize. Other runs are submitted with sbatch --wrap.

Docker container

Code
runtime = "docker"
docker_image = "simvia/code_saturne"   # optional: the solver's own image by default

use_slurm = false
max_parallel = 2

host = "127.0.0.1"
port = 8000

Containers mount the campaign folder at /csauto and start the solver inside the case folder (docker run --rm ...). Any image works:

• an image whose ENTRYPOINT is the solver, or a script that sets up the environment and starts it (modules, spack, conda, a switch to another user), gets only the solver's arguments, as before;
• an image whose ENTRYPOINT runs the command it is given (tini --, exec "$@" scripts) gets the full solver command;
• an image without ENTRYPOINT gets the solver as --entrypoint, so it must be on the image's PATH.

csauto tells the first two apart by starting the image once with true (one short container per image, the first time a csauto process launches it).

code_aster

Code
solver = "code_aster"
runtime = "docker"   # docker_image defaults to simvia/code_aster:17.4.0

max_parallel = 2

For the native runtime, run_aster must be in PATH, or solver_bin must point to it.

In containers, csauto starts run_aster with bash, after sourcing /opt/activate.sh when the image has it (the simvia/code_aster images do). A custom image needs bash, and run_aster on its PATH once that file is sourced (or from the start, when the image has no such file). An image whose ENTRYPOINT starts run_aster itself only gets its arguments.

Remote access with authentication

Code
runtime = "native"
solver_bin = "/opt/code_saturne/bin/code_saturne"
use_slurm = false
max_parallel = 4

# Expose UI to all interfaces
host = "0.0.0.0"
port = 8000

# Required when host is not 127.0.0.1 or localhost
[api]
token = "your-secret-token"

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All configuration keys

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Environment variables

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Priority rules

Runtime: CLI flags (--runtime, --solver-bin, etc.) override the TOML values.

Solver: commands on an existing campaign use the solver recorded in RUNS/campaign.json by prepare, whatever directory they run from; a different solver in csauto.toml is ignored with a warning. prepare refuses to add cases to a folder prepared for another solver.

Slurm detection order:

1. use_slurm in csauto.toml: if set, this is authoritative
2. CSAUTO_USE_SLURM environment variable
3. Auto-detection: checks if sbatch is in PATH and Slurm environment variables are set

API token: serve --token overrides [api].token from config.

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Auto runtime resolution

When runtime = "auto", csauto tries backends in this order, among the runtimes the solver supports (code_saturne and code_aster support all three):

1. Explicit solver_bin set → use native
2. Explicit singularity_image set → use singularity
3. docker command available → use docker
4. The solver's executable (code_saturne, run_aster) in PATH → use native
5. None found → error

Asking explicitly for a runtime the solver does not support is refused before anything starts.

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mpi_exec_options and Slurm

When Slurm submission is active and mpi_exec_options is set, code_saturne receives the value as:

Code
CS_MPIEXEC_OPTIONS="<mpi_exec_options>" <code_saturne run command>

With a container runtime, the variable is set inside the container instead. If not set, no CS_MPIEXEC_OPTIONS is injected. code_aster ignores this option.