Make parallel devices optional across all plugins

pytorch_lightning/plugins/training_type/ddp.py

@@ -15,7 +15,7 @@
 import subprocess
 import sys
 from time import sleep
-from typing import Any, Dict, Optional, Union
+from typing import Any, Dict, List, Optional, Union
 
 import numpy as np
 import torch
@@ -58,11 +58,11 @@ class DDPPlugin(ParallelPlugin):
 
     def __init__(
         self,
-        parallel_devices,
-        num_nodes=1,
+        parallel_devices: Optional[List[torch.device]] = None,
+        num_nodes: int = 1,
         cluster_environment: ClusterEnvironment = None,
-        sync_batchnorm=False,
-        **kwargs: Dict[str, Any],
+        sync_batchnorm: bool = False,
+        **kwargs: Union[Any, Dict[str, Any]],
     ) -> None:
         super().__init__(parallel_devices=parallel_devices, cluster_environment=cluster_environment)
         self.interactive_ddp_procs = []

pytorch_lightning/plugins/training_type/ddp_spawn.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 import os
 import re
-from typing import Any, Dict, Optional, Union
+from typing import Any, Dict, List, Optional, Union
 
 import torch
 import torch.distributed as torch_distrib
@@ -46,11 +46,11 @@ class DDPSpawnPlugin(ParallelPlugin):
 
     def __init__(
         self,
-        parallel_devices,
-        num_nodes=1,
+        parallel_devices: Optional[List[torch.device]] = None,
+        num_nodes: int = 1,
         cluster_environment: ClusterEnvironment = None,
         sync_batchnorm: bool = False,
-        **kwargs: Dict[str, Any],
+        **kwargs: Union[Any, Dict[str, Any]],
     ):
         super().__init__(parallel_devices=parallel_devices, cluster_environment=cluster_environment)
         self.num_nodes = num_nodes

pytorch_lightning/plugins/training_type/dp.py

@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from typing import List
+from typing import List, Optional
 
 import torch
 from torch.nn import DataParallel
@@ -23,7 +23,7 @@
 
 class DataParallelPlugin(ParallelPlugin):
 
-    def __init__(self, parallel_devices: List[torch.device]):
+    def __init__(self, parallel_devices: Optional[List[torch.device]]):
         super().__init__(parallel_devices=parallel_devices, cluster_environment=None)
 
     def setup(self, model):

pytorch_lightning/plugins/training_type/horovod.py

@@ -28,7 +28,7 @@
 
 class HorovodPlugin(ParallelPlugin):
 
-    def __init__(self, parallel_devices: List[torch.device]):
+    def __init__(self, parallel_devices: Optional[List[torch.device]] = None):
         super().__init__(parallel_devices=parallel_devices, cluster_environment=None)
 
     @property

pytorch_lightning/plugins/training_type/parallel.py

@@ -32,7 +32,7 @@ class ParallelPlugin(TrainingTypePlugin, ABC):
 
     def __init__(
         self,
-        parallel_devices: List[torch.device],
+        parallel_devices: Optional[List[torch.device]] = None,
         cluster_environment: Optional[ClusterEnvironment] = None,
     ):
         super().__init__()

pytorch_lightning/plugins/training_type/rpc.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 import os
 from contextlib import suppress
-from typing import Optional, Sequence
+from typing import List, Optional, Sequence
 
 import torch
 
@@ -42,7 +42,7 @@ class RPCPlugin(DDPPlugin):
     def __init__(
         self,
         rpc_timeout_sec: float = DEFAULT_RPC_TIMEOUT_SEC,
-        parallel_devices: Sequence[int] = (),
+        parallel_devices: Optional[List[torch.device]] = None,
         num_nodes: Optional[int] = None,
         cluster_environment: Optional[ClusterEnvironment] = None,
         sync_batchnorm: Optional[bool] = None,

pytorch_lightning/plugins/training_type/single_device.py

@@ -8,7 +8,7 @@
 
 class SingleDevicePlugin(TrainingTypePlugin):
 
-    def __init__(self, device: torch.device) -> bool:
+    def __init__(self, device: torch.device):
         super().__init__()
         self.device: torch.device = device
 

pytorch_lightning/plugins/training_type/tpu_spawn.py

@@ -1,7 +1,7 @@
 import io
 import os
 import re
-from typing import Any, Dict, Iterable, Optional, Sequence, Tuple, Union
+from typing import Any, Dict, Iterable, List, Optional, Sequence, Tuple, Union
 
 import torch
 import torch.multiprocessing as mp
@@ -26,7 +26,12 @@
 
 class TPUSpawnPlugin(DDPSpawnPlugin):
 
-    def __init__(self, parallel_devices: Sequence[int], num_nodes: int = 1, **kwargs: Dict[str, Any]) -> None:
+    def __init__(
+        self,
+        parallel_devices: Optional[List[torch.device]] = None,
+        num_nodes: int = 1,
+        **kwargs: Dict[str, Any]
+    ) -> None:
         super().__init__(
             parallel_devices, num_nodes=num_nodes, cluster_environment=None, sync_batchnorm=False, **kwargs
         )

pytorch_lightning/trainer/connectors/accelerator_connector.py

@@ -405,7 +405,7 @@ def select_training_type_plugin(self) -> TrainingTypePlugin:
         return plugin
 
     def resolve_training_type_plugin(self, training_type: TrainingTypePlugin) -> TrainingTypePlugin:
-        # necessary for RPC, when user has to provide balance
+        # necessary for when the user has passed in a plugin
         if hasattr(training_type, 'parallel_devices') and not getattr(training_type, 'parallel_devices'):
             training_type.parallel_devices = self.parallel_devices
             if hasattr(training_type, 'num_processes'):