Bug - Fix issue that the root mpi rank may not be the first in the hostfile (#270)

**Description**
Launch mpi on the sorted first host in the hostfile.

superbench/runner/ansible.py

@@ -26,6 +26,7 @@ def __init__(self, config):
             'host_pattern': 'localhost',
             'cmdline': '--forks 128',
         }
+        self._head_host = None
         if config:
             inventory_file = getattr(config, 'host_file', None)
             inventory_list = getattr(config, 'host_list', None)
@@ -34,9 +35,10 @@ def __init__(self, config):
             if inventory_file or inventory_list:
                 self._config['host_pattern'] = 'all'
                 inventory = InventoryManager(loader=DataLoader(), sources=inventory_file or f'{inventory_list},')
-                host_list = inventory.get_groups_dict()['all']
+                host_list = inventory.get_hosts(pattern='all', order='sorted')
                 if len(host_list) > 0:
                     self._config['cmdline'] = '--forks {}'.format(len(host_list))
+                    self._head_host = host_list[0].get_name()
                 if inventory_list in ['localhost', '127.0.0.1']:
                     self._config['cmdline'] += ' --connection local'
                 self._config['cmdline'] += ' --inventory {}'.format(inventory_file or f'{inventory_list},')
@@ -87,7 +89,10 @@ def update_mpi_config(self, ansible_config):
         Returns:
             dict: Updated Ansible config dict.
         """
-        ansible_config['host_pattern'] += '[0]'
+        if not self._head_host:
+            ansible_config['host_pattern'] += '[0]'
+        else:
+            ansible_config['host_pattern'] = self._head_host
         return ansible_config
 
     def get_shell_config(self, cmd):

tests/runner/test_ansible.py

@@ -38,10 +38,12 @@ def setUp(self):
                 'host_password': 'pass',
             })
         )
+        _, self.test_mpi_host_file = tempfile.mkstemp()
 
     def tearDown(self):
         """Hook method for deconstructing the test fixture after testing it."""
         Path(self.host_file).unlink()
+        Path(self.test_mpi_host_file).unlink()
 
     def test_init_config(self):
         """Test initial config of client."""
@@ -61,6 +63,63 @@ def test_update_mpi_config(self):
         self.assertDictEqual(
             self.ansible_client.update_mpi_config(self.ansible_client._config), {
                 **self.ansible_client._config,
+                'host_pattern': '10.0.0.10',
+            }
+        )
+
+    def test_update_mpi_config_for_different_inventory(self):
+        """Test update_mpi_config of client for different inventory."""
+        # Test for out-of-order
+        with open(self.test_mpi_host_file, 'w') as fd:
+            fd.write('all:\n  hosts:\n    10.0.0.12:\n    10.0.0.11:\n    10.0.0.10:\n    10.0.0.13:\n    10.0.0.14:\n')
+        mess_hosts = AnsibleClient(
+            OmegaConf.create(
+                {
+                    'host_file': self.test_mpi_host_file,
+                    'host_username': 'user',
+                    'host_password': 'pass',
+                }
+            )
+        )
+        self.assertDictEqual(
+            mess_hosts.update_mpi_config(mess_hosts._config), {
+                **mess_hosts._config,
+                'host_pattern': '10.0.0.10',
+            }
+        )
+        # Test for localhost
+        with open(self.test_mpi_host_file, 'w') as fd:
+            fd.write('all:\n  hosts:\n    localhost:\n')
+        localhost = AnsibleClient(
+            OmegaConf.create(
+                {
+                    'host_file': self.test_mpi_host_file,
+                    'host_username': 'user',
+                    'host_password': 'pass',
+                }
+            )
+        )
+        self.assertDictEqual(
+            localhost.update_mpi_config(localhost._config), {
+                **localhost._config,
+                'host_pattern': 'localhost',
+            }
+        )
+        # Test for no host
+        with open(self.test_mpi_host_file, 'w') as fd:
+            fd.write('all:\n  hosts:\n')
+        no_hosts = AnsibleClient(
+            OmegaConf.create(
+                {
+                    'host_file': self.test_mpi_host_file,
+                    'host_username': 'user',
+                    'host_password': 'pass',
+                }
+            )
+        )
+        self.assertDictEqual(
+            no_hosts.update_mpi_config(no_hosts._config), {
+                **no_hosts._config,
                 'host_pattern': 'all[0]',
             }
         )