fix horovod

Author: four4fish

pytorch_lightning/strategies/horovod.py

@@ -36,7 +36,7 @@
 class HorovodStrategy(ParallelStrategy):
     """Plugin for Horovod distributed training integration."""
 
-    distributed_backend = "horovod"
+    # distributed_backend = "horovod"
 
     def __init__(
         self,
@@ -197,11 +197,15 @@ def _filter_named_parameters(model: nn.Module, optimizer: Optimizer) -> List[Tup
 
     @classmethod
     def register_strategies(cls, strategy_registry: Dict) -> None:
-        strategy_registry.register(
-            cls.distributed_backend,
-            cls,
-            description=f"{cls.__class__.__name__} Strategy",
-        )
+        if _HOROVOD_AVAILABLE:
+            import horovod.torch as hvd
+            hvd.init()
+
+            strategy_registry.register(
+                cls.distributed_backend,
+                cls,
+                description=f"{cls.__class__.__name__} Strategy",
+            )
 
     def teardown(self) -> None:
         super().teardown()