Ensure accelerator is valid if running interactively

pytorch_lightning/accelerators/accelerator_connector.py

@@ -82,6 +82,7 @@ def __init__(
         # initialization
         self._device_type = DeviceType.CPU
         self._distrib_type = None
+        self.ipython_compatible_distrib_types = [DistributedType.DP, DistributedType.DDP_SPAWN, DistributedType.DDP_SHARDED_SPAWN]
 
         self.num_processes = num_processes
         self.tpu_cores = device_parser.parse_tpu_cores(tpu_cores)
@@ -500,7 +501,10 @@ def set_distributed_mode(self, distributed_backend: Optional[str] = None):
             else:
                 rank_zero_warn('You are running on single node with no parallelization, so distributed has no effect.')
                 self._distrib_type = None
-
+
+        # finished configuring self._distrib_type, check ipython environment
+        self.check_ipython_compatibility()
+
         # for DDP overwrite nb processes by requested GPUs
         if (
             self._device_type == DeviceType.GPU
@@ -542,6 +546,27 @@ def _set_horovod_backend(self):
         else:
             self.num_processes = hvd.local_size()
 
+    def check_ipython_compatibility(self):
+        """Raises a `MisconfigurationException` if the accelerator is not compatible with IPython and code is run in an IPython kernel."""
+        if self._distrib_type not in self.ipython_compatible_distrib_types:
+            # check ipython env
+            import sys
+            in_ipython = False
+            in_ipython_kernel = False
+            if 'IPython' in sys.modules:
+                from IPython import get_ipython
+                ip = get_ipython()
+                in_ipython = ip is not None
+
+            if in_ipython:
+                in_ipython_kernel = getattr(ip, 'kernel', None) is not None
+
+            if in_ipython_kernel:
+                raise MisconfigurationException(
+            "Selected distributed backend {self._distrib_type} not compatible with IPython environment"
+            "Run your code as a script, or choose one of compatible backends {self.ipython_compatible_distrib_types} as accelerator backend"
+            )
+
     def check_horovod(self):
         """Raises a `MisconfigurationException` if the Trainer is not configured correctly for Horovod."""
         if not _HOROVOD_AVAILABLE: