diff --git a/jarvis_util/shell/mpi_exec.py b/jarvis_util/shell/mpi_exec.py
index f72abca..30e5419 100644
--- a/jarvis_util/shell/mpi_exec.py
+++ b/jarvis_util/shell/mpi_exec.py
@@ -144,9 +144,11 @@ def __init__(self, cmd, exec_info):
     def mpicmd(self):
         params = [f'mpiexec -n {self.nprocs}']
         if self.ppn is not None:
-            params.append(f'-ppn {self.ppn}')
+            params.append(f'--ppn {self.ppn}')
         if len(self.hostfile):
-            if self.hostfile.is_subset() or self.hostfile.path is None:
+            if self.hostfile.hosts[0] == 'localhost' and len(self.hostfile) == 1:
+                pass
+            elif self.hostfile.is_subset() or self.hostfile.path is None:
                 params.append(f'--hosts {",".join(self.hostfile.hosts)}')
             else:
                 params.append(f'--hostfile {self.hostfile.path}')