Release (#467)

* smurf ethics

* smurf ethics

* removed auto ddp fix

* removed auto ddp fix

* removed auto ddp fix

* removed auto ddp fix

* removed auto ddp fix

* removed auto ddp fix

Author: williamFalcon

pytorch_lightning/trainer/ddp_mixin.py

@@ -49,14 +49,13 @@ def set_distributed_mode(self, distributed_backend, nb_gpu_nodes):
                     'Trainer(distributed_backend=dp) (or ddp)'
                 raise MisconfigurationException(m)
 
-        # use ddp automatically if nb_gpu_nodes > 1
-        if nb_gpu_nodes > 1 and self.use_dp:  # pragma: no cover
-            self.use_ddp = True
-            self.use_dp = False
+        # throw error to force user ddp or ddp2 choice
+        if nb_gpu_nodes > 1 and not (self.use_ddp2 or self.use_ddp):  # pragma: no cover
             w = 'DataParallel does not support nb_gpu_nodes > 1. ' \
                 'Switching to DistributedDataParallel for you. ' \
-                'To silence this warning set distributed_backend=ddp'
-            warnings.warn(w)
+                'To silence this warning set distributed_backend=ddp' \
+                'or distributed_backend=ddp2'
+            raise MisconfigurationException(w)
 
         logging.info(f'gpu available: {torch.cuda.is_available()}, used: {self.on_gpu}')
 
@@ -173,7 +172,7 @@ def ddp_train(self, gpu_nb, model):
         if self.distributed_backend == 'ddp':
             device_ids = [gpu_nb]
         elif self.use_ddp2:
-            device_ids = None
+            device_ids = self.data_parallel_device_ids
 
         # allow user to configure ddp
         model = model.configure_ddp(model, device_ids)