Add gpu pickleable module to torch

src/garage/torch/__init__.py

@@ -4,7 +4,7 @@
                                      compute_advantages, expand_var,
                                      filter_valids, flatten_batch,
                                      flatten_to_single_vector, global_device,
-                                     NonLinearity, output_height_2d,
+                                     Module, NonLinearity, output_height_2d,
                                      output_width_2d, pad_to_last, prefer_gpu,
                                      product_of_gaussians, set_gpu_mode,
                                      soft_update_model, state_dict_to,
@@ -31,4 +31,5 @@
     'output_height_2d',
     'expand_var',
     'state_dict_to',
+    'Module',
 ]

src/garage/torch/_functions.py

@@ -331,11 +331,11 @@ def state_dict_to(state_dict, device):
     """Move optimizer to a specified device.
 
     Args:
-        state_dict (dict): state dictionary to be moved
+        state_dict (dict): state dictionary to be moved.
         device (str): ID of GPU or CPU.
 
     Returns:
-        dict: state dictionary moved to device
+        dict: state dictionary moved to device.
     """
     for param in state_dict.values():
         if isinstance(param, torch.Tensor):
@@ -345,6 +345,61 @@ def state_dict_to(state_dict, device):
     return state_dict
 
 
+# pylint: disable=abstract-method
+class Module(nn.Module):
+    """Wrapper class for Garage PyTorch modules."""
+
+    def __getstate__(self):
+        """Save the current device of the module before saving module state.
+
+        Returns:
+            dict: State dictionary.
+        """
+        # do we always run experiments on global device?
+        save_from_device = global_device()
+        self.to('cpu')
+        state = self.__dict__.copy()
+        state['device'] = save_from_device
+        return state
+
+    def __setstate__(self, state):
+        """Restore the module state, moving it back to the original device if possible.
+
+        Args:
+            state (dict): State dictionary.
+
+        """
+        system_device = global_device()
+        save_from_device = state['device']
+        if save_from_device == system_device:
+            module_state_to(state, system_device)
+        # what to do if it doesn't match?
+        # do I need to set global device to the current device?
+        del state['device']
+        self.__dict__ = state
+        if save_from_device == system_device:
+            self.to(system_device)
+
+
+def module_state_to(state, device):
+    """Move elements of a module state to a device.
+
+    Notes - are there other types of parameters in a
+    module state to be moved? are some of them recursive?
+
+    Args:
+        state (dict): State dictionary.
+        device (str): ID of GPU or CPU.
+
+    Returns:
+        dict: moved state dict.
+    """
+    for param in state.values():
+        if hasattr(param, 'to'):
+            param = param.to(device)
+    return state
+
+
 # pylint: disable=W0223
 class NonLinearity(nn.Module):
     """Wrapper class for non linear function or module.

src/garage/torch/policies/policy.py

@@ -1,12 +1,11 @@
 """Base Policy."""
 import abc
 
-import torch
-
 from garage.np.policies import Policy as BasePolicy
+from garage.torch import Module
 
 
-class Policy(torch.nn.Module, BasePolicy, abc.ABC):
+class Policy(Module, BasePolicy, abc.ABC):
     """Policy base class.
 
     Args:

tests/garage/torch/policies/test_categorical_cnn_policy.py

@@ -4,6 +4,7 @@
 import torch
 
 from garage.envs import GymEnv
+from garage.torch import global_device, set_gpu_mode
 from garage.torch.policies import CategoricalCNNPolicy
 
 from tests.fixtures.envs.dummy import DummyDictEnv, DummyDiscretePixelEnv
@@ -152,3 +153,36 @@ def test_obs_unflattened(self, hidden_channels, kernel_sizes, strides,
         obs = env.observation_space.sample()
         action, _ = policy.get_action(env.observation_space.flatten(obs))
         env.step(action)
+
+
+@pytest.mark.gpu
+@pytest.mark.parametrize(
+    'hidden_channels, kernel_sizes, strides, hidden_sizes', [
+        ((3, ), (3, ), (1, ), (4, )),
+        ((3, 3), (3, 3), (1, 1), (4, 4)),
+        ((3, 3), (3, 3), (2, 2), (4, 4)),
+    ])
+def test_is_pickleable_on_gpu(hidden_channels, kernel_sizes, strides,
+                              hidden_sizes):
+    """Test if policy is pickable when on gpu."""
+    set_gpu_mode(True)
+    env = GymEnv(DummyDiscretePixelEnv(), is_image=True)
+    policy = CategoricalCNNPolicy(env_spec=env.spec,
+                                  image_format='NHWC',
+                                  kernel_sizes=kernel_sizes,
+                                  hidden_channels=hidden_channels,
+                                  strides=strides,
+                                  hidden_sizes=hidden_sizes)
+    policy.to(global_device())
+    env.reset()
+    obs = env.step(1).observation
+
+    output_action_1, _ = policy.get_action(obs)
+
+    p = cloudpickle.dumps(policy)
+    policy_pickled = cloudpickle.loads(p)
+    output_action_2, _ = policy_pickled.get_action(obs)
+
+    assert env.action_space.contains(output_action_1)
+    assert env.action_space.contains(output_action_2)
+    assert output_action_1.shape == output_action_2.shape