Add a class to freeze parameters

DPI/utils.py

@@ -17,6 +17,7 @@ import dmc2gym
 
 import cv2
 from PIL import Image
+from typing import Iterable
 
 
 class eval_mode(object):
@@ -197,6 +198,12 @@ def make_env(args):
         )
     return env
 
+def soft_update_params(net, target_net, tau):
+    for param, target_param in zip(net.parameters(), target_net.parameters()):
+        target_param.data.copy_(
+            tau * param.data + (1 - tau) * target_param.data
+        )
+
 def save_image(array, filename):
     array = array.transpose(1, 2, 0)
     array = (array * 255).astype(np.uint8)
@@ -256,4 +263,40 @@ class CorruptVideos:
                     print(f"{filepath} is corrupt.")
                     if delete:
                         self._delete_corrupt_video(filepath)
-                        print(f"Deleted {filepath}")
+                        print(f"Deleted {filepath}")
+
+
+def get_parameters(modules: Iterable[nn.Module]):
+    """
+    Given a list of torch modules, returns a list of their parameters.
+    :param modules: iterable of modules
+    :returns: a list of parameters
+    """
+    model_parameters = []
+    for module in modules:
+        model_parameters += list(module.parameters())
+    return model_parameters
+
+class FreezeParameters:
+    def __init__(self, modules: Iterable[nn.Module]):
+        """
+        Context manager to locally freeze gradients.
+        In some cases with can speed up computation because gradients aren't calculated for these listed modules.
+        example:
+        ```
+        with FreezeParameters([module]):
+          output_tensor = module(input_tensor)
+        ```
+        :param modules: iterable of modules. used to call .parameters() to freeze gradients.
+        """
+        self.modules = modules
+        self.param_states = [p.requires_grad for p in get_parameters(self.modules)]
+
+    def __enter__(self):
+
+        for param in get_parameters(self.modules):
+            param.requires_grad = False
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        for i, param in enumerate(get_parameters(self.modules)):
+            param.requires_grad = self.param_states[i]