Merge pull request #73 from zwicker-group/mpi_guard

Prevent writing results in sub-nodes of an MPI program

modelrunner/model/base.py

@@ -16,6 +16,15 @@
 from ..storage import ModeType, StorageGroup, open_storage
 from .parameters import DeprecatedParameter, HideParameter, Parameterized
 
+# read state of the current MPI node
+try:
+    from mpi4py import MPI
+except ImportError:
+    mpi_rank: int = 0  # no MPI -> current process is main process
+else:
+    mpi_rank = MPI.COMM_WORLD.rank
+
+
 if TYPE_CHECKING:
     from ..run.results import Result  # @UnusedImport
 
@@ -223,13 +232,13 @@ def run_from_command_line(
 
         # run the model
         result = mdl.get_result()
-        if mdl.output:
-            # write the results to a file
+
+        # write the results
+        if mdl.output and mpi_rank == 0:
+            # Write the results to a file if `output` is specified and if we are on the
+            # root node of an MPI run (or a serial program). The second check is a
+            # safe-guard against writing data on sub-nodes during an MPI program.
             mdl.write_result(result=result)
-        # else:
-        #     # display the results on stdout
-        #     storage = MemoryStorage()
-        #     result.to_file(storage)
 
         # close the output file
         mdl.close()