libEnsemble with Flux¶

Flux is a flexible, hierarchical resource manager and job scheduler used on a growing number of systems, including LLNL’s El Capitan.

libEnsemble can read Flux resource lists and partition these to workers. By default this is done by reading an environment variable (FLUX_URI), which is then used to query flux resource list for the available nodes.

There are two independent ways to run applications under Flux with libEnsemble; see the Flux Executor page for a full comparison and usage examples of both:

Tell the MPIExecutor to use flux run as its launcher, either directly:

from libensemble.executors import MPIExecutor
exctr = MPIExecutor(custom_info={"mpi_runner": "flux"})

or via the built-in flux platform:

libE_specs["platform"] = "flux"

Use the native FluxExecutor, which submits jobs directly to Flux via its Python API instead of subprocessing a launcher. This requires the flux-core Python bindings and is particularly useful in containerized environments:
```
from libensemble.executors.flux_executor import FluxExecutor
exctr = FluxExecutor()
```