[Feature] COMPOSITE_LP_AGGREGATE env variable

ghstack-source-id: 16b07d0eac582cfd419612f87e38e1a7acffcfc0
Pull Request resolved: #1190

tensordict/nn/utils.py

@@ -450,7 +450,13 @@ def _generate_next_value_(name, start, count, last_values):
         return name.lower()
 
 
-_composite_lp_aggregate = _ContextManager()
+_composite_lp_aggregate = _ContextManager(
+    default=(
+        strtobool(os.getenv("COMPOSITE_LP_AGGREGATE"))
+        if os.getenv("COMPOSITE_LP_AGGREGATE") is not None
+        else None
+    )
+)
 
 
 def composite_lp_aggregate(nowarn: bool = False) -> bool | None:
@@ -467,9 +473,9 @@ def composite_lp_aggregate(nowarn: bool = False) -> bool | None:
         if not nowarn:
             warnings.warn(
                 "Composite log-prob aggregation wasn't defined explicitly and ``composite_lp_aggregate()`` will "
-                "currently return ``True``. However, from v0.9, this behaviour will change and ``composite_lp_aggregate`` will "
+                "currently return ``True``. However, from v0.9, this behavior will change and ``composite_lp_aggregate`` will "
                 "return ``False``. Please change your code accordingly by specifying the aggregation strategy via "
-                "`tensordict.nn.set_composite_lp_aggregate`.",
+                "`tensordict.nn.set_composite_lp_aggregate` or via the `COMPOSITE_LP_AGGREGATE` environment variable.",
                 category=DeprecationWarning,
             )
         return True
@@ -483,6 +489,8 @@ class set_composite_lp_aggregate(_DecoratorContextManager):
     will be summed into a single tensor with the shape of the root tensordict. This behaviour is being deprecated in favor of
     non-aggregated log-probs, which offer more flexibility and a somewhat more natural API (tensordict samples, tensordict log-probs, tensordict entropies).
 
+    The value of composite_lp_aggregate can also be controlled through the `COMPOSITE_LP_AGGREGATE` environment variable.
+
     Example:
         >>> _ = torch.manual_seed(0)
         >>> from tensordict import TensorDict