diff --git a/pytorch_lightning/trainer/data_loading.py b/pytorch_lightning/trainer/data_loading.py
index 7d0b8180..b3e15024 100644
--- a/pytorch_lightning/trainer/data_loading.py
+++ b/pytorch_lightning/trainer/data_loading.py
@@ -133,6 +133,7 @@ class TrainerDataLoadingMixin(ABC):
                 world_size = {
                     'ddp': self.num_nodes * self.num_processes,
                     'ddp2': self.num_nodes,
+                    'ddp_cpu': self.num_processes * self.num_nodes
                 }
                 sampler = DistributedSampler(
                     dataloader.dataset,
diff --git a/pytorch_lightning/trainer/trainer.py b/pytorch_lightning/trainer/trainer.py
index eeafb73f..deed0098 100644
--- a/pytorch_lightning/trainer/trainer.py
+++ b/pytorch_lightning/trainer/trainer.py
@@ -614,17 +614,8 @@ class Trainer(
                         return bool(parsing.strtobool(x))
 
                 if arg == 'gpus':
-                    def allowed_type(x):
-                        if ',' in x:
-                            return str(x)
-                        else:
-                            return int(x)
-
-                    def arg_default(x):
-                        if ',' in x:
-                            return str(x)
-                        else:
-                            return int(x)
+                    allowed_type = Trainer.allowed_type
+                    arg_default = Trainer.arg_default
 
                 parser.add_argument(
                     f'--{arg}',
@@ -637,6 +628,18 @@ class Trainer(
 
         return parser
 
+    def allowed_type(x):
+        if ',' in x:
+            return str(x)
+        else:
+            return int(x)
+
+    def arg_default(x):
+        if ',' in x:
+            return str(x)
+        else:
+            return int(x)
+
     @classmethod
     def from_argparse_args(cls, args, **kwargs):
 
@@ -711,6 +714,10 @@ class Trainer(
         model.logger = self.logger
         self.copy_trainer_model_properties(model)
 
+        # clean hparams
+        if hasattr(model, 'hparams'):
+            parsing.clean_namespace(model.hparams)
+
         # set up the passed in dataloaders (if needed)
         self.__attach_dataloaders(model, train_dataloader, val_dataloaders)
 
diff --git a/pytorch_lightning/trainer/training_io.py b/pytorch_lightning/trainer/training_io.py
index 4bb3c406..82bc0829 100644
--- a/pytorch_lightning/trainer/training_io.py
+++ b/pytorch_lightning/trainer/training_io.py
@@ -101,7 +101,7 @@ from pytorch_lightning.overrides.data_parallel import (
     LightningDistributedDataParallel,
     LightningDataParallel,
 )
-from pytorch_lightning.utilities import rank_zero_warn
+from pytorch_lightning.utilities import rank_zero_warn, parsing
 
 try:
     import torch_xla
@@ -325,7 +325,7 @@ class TrainerIOMixin(ABC):
             checkpoint['native_amp_scaling_state'] = self.scaler.state_dict()
 
         if hasattr(model, "hparams"):
-            self.__clean_namespace(model.hparams)
+            parsing.clean_namespace(model.hparams)
             is_namespace = isinstance(model.hparams, Namespace)
             checkpoint['hparams'] = vars(model.hparams) if is_namespace else model.hparams
             checkpoint['hparams_type'] = 'namespace' if is_namespace else 'dict'
@@ -339,31 +339,6 @@ class TrainerIOMixin(ABC):
 
         return checkpoint
 
-    def __clean_namespace(self, hparams):
-        """
-        Removes all functions from hparams so we can pickle
-        :param hparams:
-        :return:
-        """
-
-        if isinstance(hparams, Namespace):
-            del_attrs = []
-            for k in hparams.__dict__:
-                if callable(getattr(hparams, k)):
-                    del_attrs.append(k)
-
-            for k in del_attrs:
-                delattr(hparams, k)
-
-        elif isinstance(hparams, dict):
-            del_attrs = []
-            for k, v in hparams.items():
-                if callable(v):
-                    del_attrs.append(k)
-
-            for k in del_attrs:
-                del hparams[k]
-
     # --------------------
     # HPC IO
     # --------------------
diff --git a/pytorch_lightning/utilities/parsing.py b/pytorch_lightning/utilities/parsing.py
index 26fc410d..2549e485 100644
--- a/pytorch_lightning/utilities/parsing.py
+++ b/pytorch_lightning/utilities/parsing.py
@@ -1,3 +1,6 @@
+from argparse import Namespace
+
+
 def strtobool(val):
     """Convert a string representation of truth to true (1) or false (0).
     Copied from the python implementation distutils.utils.strtobool
@@ -18,3 +21,29 @@ def strtobool(val):
         return 0
     else:
         raise ValueError(f'invalid truth value {val}')
+
+
+def clean_namespace(hparams):
+    """
+    Removes all functions from hparams so we can pickle
+    :param hparams:
+    :return:
+    """
+
+    if isinstance(hparams, Namespace):
+        del_attrs = []
+        for k in hparams.__dict__:
+            if callable(getattr(hparams, k)):
+                del_attrs.append(k)
+
+        for k in del_attrs:
+            delattr(hparams, k)
+
+    elif isinstance(hparams, dict):
+        del_attrs = []
+        for k, v in hparams.items():
+            if callable(v):
+                del_attrs.append(k)
+
+        for k in del_attrs:
+            del hparams[k]
diff --git a/tests/trainer/test_trainer_cli.py b/tests/trainer/test_trainer_cli.py
index bfc67111..93cbb8e2 100644
--- a/tests/trainer/test_trainer_cli.py
+++ b/tests/trainer/test_trainer_cli.py
@@ -47,6 +47,11 @@ def test_add_argparse_args_redefined(cli_args):
         assert depr_name not in args
 
     trainer = Trainer.from_argparse_args(args=args)
+
+    # make sure trainer can be pickled
+    import pickle
+    pickle.dumps(trainer)
+
     assert isinstance(trainer, Trainer)