Update

[ghstack-poisoned]

torchrl/envs/common.py

@@ -2699,6 +2699,7 @@ def specs(self) -> Composite:
 
     @property
     def _has_dynamic_specs(self) -> bool:
+        # TODO: cache this value
         return _has_dynamic_specs(self.specs)
 
     def rollout(
@@ -2711,7 +2712,7 @@ def rollout(
         auto_cast_to_device: bool = False,
         break_when_any_done: bool | None = None,
         break_when_all_done: bool | None = None,
-        return_contiguous: bool = True,
+        return_contiguous: bool | None = False,
         tensordict: Optional[TensorDictBase] = None,
         set_truncated: bool = False,
         out=None,
@@ -2746,7 +2747,8 @@ def rollout(
             break_when_all_done (bool, optional): if ``True``, break if all of the contained environments reach any
                 of the done states. If ``False``, break if at least one environment reaches any of the done states.
                 Default is ``False``.
-            return_contiguous (bool): if False, a LazyStackedTensorDict will be returned. Default is True.
+            return_contiguous (bool): if False, a LazyStackedTensorDict will be returned. Default is `True` if
+                the env does not have dynamic specs, otherwise `False`.
             tensordict (TensorDict, optional): if ``auto_reset`` is False, an initial
                 tensordict must be provided. Rollout will check if this tensordict has done flags and reset the
                 environment in those dimensions (if needed).
@@ -2957,7 +2959,8 @@ def rollout(
             raise TypeError(
                 "Cannot have both break_when_all_done and break_when_any_done True at the same time."
             )
-
+        if return_contiguous is None:
+            return_contiguous = not self._has_dynamic_specs
         if policy is not None:
             policy = _make_compatible_policy(
                 policy,