Let Accelerator inherit from ABC to make sure abstractmethod takes effect (#11521)

pytorch_lightning/accelerators/accelerator.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 abc import abstractmethod
+from abc import ABC, abstractmethod
 from typing import Any, Dict, Union
 
 import torch
@@ -19,7 +19,7 @@ import torch
 import pytorch_lightning as pl
 
 
-class Accelerator:
+class Accelerator(ABC):
     """The Accelerator Base Class. An Accelerator is meant to deal with one type of Hardware.
 
     Currently there are accelerators for:
@@ -45,7 +45,7 @@ class Accelerator:
         """
 
     def get_device_stats(self, device: Union[str, torch.device]) -> Dict[str, Any]:
-        """Gets stats for a given device.
+        """Get stats for a given device.
 
         Args:
             device: device for which to get stats
@@ -58,4 +58,4 @@ class Accelerator:
     @staticmethod
     @abstractmethod
     def auto_device_count() -> int:
-        """Get the devices when set to auto."""
+        """Get the device count when set to auto."""

tests/accelerators/test_accelerator_connector.py

@@ -336,7 +336,9 @@ def test_accelerator_choice_ddp_cpu_custom_cluster(_, tmpdir):
 @mock.patch("pytorch_lightning.strategies.DDPStrategy.setup_distributed", autospec=True)
 def test_custom_accelerator(device_count_mock, setup_distributed_mock):
     class Accel(Accelerator):
-        pass
+        @staticmethod
+        def auto_device_count() -> int:
+            return 1
 
     class Prec(PrecisionPlugin):
         pass