Add ddp_find_unused_parameters_false to Registry (#7224)

pytorch_lightning/plugins/training_type/ddp.py

@@ -330,3 +330,12 @@ class DDPPlugin(ParallelPlugin):
     def post_training_step(self):
         if not self.lightning_module.automatic_optimization:
             self.model.require_backward_grad_sync = True
+
+    @classmethod
+    def register_plugins(cls, plugin_registry: Dict) -> None:
+        plugin_registry.register(
+            "ddp_find_unused_parameters_false",
+            cls,
+            description="DDP Plugin with `find_unused_parameters` as False",
+            find_unused_parameters=False
+        )

tests/plugins/test_plugins_registry.py

@@ -14,8 +14,7 @@
 import pytest
 
 from pytorch_lightning import Trainer
-from pytorch_lightning.plugins import TrainingTypePluginsRegistry
-from pytorch_lightning.plugins.training_type.deepspeed import DeepSpeedPlugin
+from pytorch_lightning.plugins import DDPPlugin, DeepSpeedPlugin, TrainingTypePluginsRegistry
 from tests.helpers.runif import RunIf
 
 
@@ -75,7 +74,7 @@ def test_training_type_plugins_registry_with_deepspeed_plugins(plugin_name, init
 
 @RunIf(deepspeed=True)
 @pytest.mark.parametrize("plugin", ["deepspeed", "deepspeed_stage_2_offload", "deepspeed_stage_3"])
-def test_training_type_plugins_registry_with_trainer(tmpdir, plugin):
+def test_deepspeed_training_type_plugins_registry_with_trainer(tmpdir, plugin):
 
     trainer = Trainer(
         default_root_dir=tmpdir,
@@ -84,3 +83,13 @@ def test_training_type_plugins_registry_with_trainer(tmpdir, plugin):
     )
 
     assert isinstance(trainer.training_type_plugin, DeepSpeedPlugin)
+
+
+def test_ddp_training_type_plugins_registry_with_trainer(tmpdir):
+
+    trainer = Trainer(
+        default_root_dir=tmpdir,
+        plugins="ddp_find_unused_parameters_false",
+    )
+
+    assert isinstance(trainer.training_type_plugin, DDPPlugin)