Error handling for accelerator="mps" and ddp strategy pairing

src/pytorch_lightning/trainer/connectors/accelerator_connector.py

@@ -283,6 +283,25 @@ def _check_config_and_set_final_flags(
                 f" Available names are: {', '.join(self._accelerator_types)}."
             )
 
+        # mps accelerator incompatible with ddp-family
+        ddp_classes = (
+                            DDPStrategy,
+                            DDPSpawnShardedStrategy,
+                            DDPShardedStrategy,
+                            DDPFullyShardedNativeStrategy,
+                            DDPFullyShardedStrategy,
+                            DDPSpawnStrategy,
+                        )
+        is_ddp_str = isinstance(strategy, str) and "ddp" in strategy
+        if (
+            accelerator is not None
+            and strategy is not None
+            and (isinstance(accelerator, str) and accelerator == "mps")
+            and (is_ddp_str or (isinstance(strategy, ddp_classes))
+            )
+        ):
+            raise MisconfigurationException("With `accelerator=mps`, strategies from DDP Family are not compatible")
+
         self._accelerator_flag = accelerator
 
         if precision is not None:

tests/tests_pytorch/trainer/connectors/test_accelerator_connector.py

@@ -369,6 +369,33 @@ def test_exception_invalid_strategy():
         Trainer(strategy="tpu_spawn")
 
 
+@pytest.mark.parametrize(
+    ["strategy", "strategy_class"],
+    (
+        ("ddp_spawn", DDPSpawnStrategy),
+        ("ddp_spawn_find_unused_parameters_false", DDPSpawnStrategy),
+        ("ddp", DDPStrategy),
+        ("ddp_find_unused_parameters_false", DDPStrategy),
+        ("dp", DataParallelStrategy),
+        ("ddp_sharded", DDPShardedStrategy),
+        ("ddp_sharded_spawn", DDPSpawnShardedStrategy),
+    ),
+)
+@RunIf(mps=True)
+def test_exception_invalid_ddp_strategy_with_mps(strategy, strategy_class):
+    # check with str
+    with pytest.raises(
+        MisconfigurationException, match=r"With `accelerator=mps`, strategies from DDP Family are not compatible"
+    ):
+        Trainer(accelerator="mps", strategy=strategy)
+
+    # check with instance
+    with pytest.raises(
+        MisconfigurationException, match=r"With `accelerator=mps`, strategies from DDP Family are not compatible"
+    ):
+        Trainer(accelerator="mps", strategy=strategy_class())
+
+
 @pytest.mark.parametrize(
     ["strategy", "strategy_class"],
     [