Raise error when srun is not available

pympipool/__init__.py

@@ -1,11 +1,15 @@
 from ._version import get_versions
 from pympipool.mpi.executor import PyMPIExecutor
-from pympipool.slurm.executor import PySlurmExecutor
 
 try:  # The PyFluxExecutor requires flux-core to be installed.
     from pympipool.flux.executor import PyFluxExecutor
 except ImportError:
     pass
 
+try:  # The PySlurmExecutor requires the srun command to be available.
+    from pympipool.slurm.executor import PySlurmExecutor
+except ImportError:
+    pass
+
 __version__ = get_versions()["version"]
 del get_versions

pympipool/shared/interface.py

@@ -2,6 +2,10 @@
 import subprocess
 
 
+MPI_COMMAND = "mpiexec"
+SLURM_COMMAND = "srun"
+
+
 class BaseInterface(ABC):
     def __init__(self, cwd, cores=1, oversubscribe=False):
         self._cwd = cwd
@@ -94,7 +98,7 @@ def generate_command(self, command_lst):
 
 
 def generate_mpiexec_command(cores, oversubscribe=False):
-    command_prepend_lst = ["mpiexec", "-n", str(cores)]
+    command_prepend_lst = [MPI_COMMAND, "-n", str(cores)]
     if oversubscribe:
         command_prepend_lst += ["--oversubscribe"]
     return command_prepend_lst
@@ -103,7 +107,7 @@ def generate_mpiexec_command(cores, oversubscribe=False):
 def generate_slurm_command(
     cores, cwd, threads_per_core=1, gpus_per_core=0, oversubscribe=False
 ):
-    command_prepend_lst = ["srun", "-n", str(cores)]
+    command_prepend_lst = [SLURM_COMMAND, "-n", str(cores)]
     if cwd is not None:
         command_prepend_lst += ["-D", cwd]
     if threads_per_core > 1:

pympipool/slurm/executor.py

@@ -1,13 +1,21 @@
+import shutil
+import subprocess
+
+
 from pympipool.shared.executorbase import (
     cloudpickle_register,
     execute_parallel_tasks,
     ExecutorBase,
     executor_broker,
 )
-from pympipool.shared.interface import SrunInterface
+from pympipool.shared.interface import SrunInterface, SLURM_COMMAND
 from pympipool.shared.thread import RaisingThread
 
 
+if shutil.which(SLURM_COMMAND) is None:
+    raise ImportError("SLURM command " + SLURM_COMMAND + " not found.")
+
+
 class PySlurmExecutor(ExecutorBase):
     """
     Args: