[BugFix] Make functorch.dim optional

tensordict/_lazy.py

@@ -21,7 +21,15 @@
 import numpy as np
 import torch
 import torch.distributed as dist
-from functorch import dim as ftdim
+
+try:
+    from functorch import dim as ftdim
+
+    _has_funcdim = True
+except ImportError:
+    from tensordict.utils import _ftdim_mock as ftdim
+
+    _has_funcdim = False
 from tensordict._td import _SubTensorDict, _TensorDictKeysView, TensorDict
 from tensordict._tensordict import _unravel_key_to_tuple, unravel_key_list
 from tensordict.base import (

tensordict/_td.py

@@ -20,7 +20,15 @@
 
 import numpy as np
 import torch
-from functorch import dim as ftdim
+
+try:
+    from functorch import dim as ftdim
+
+    _has_funcdim = True
+except ImportError:
+    from tensordict.utils import _ftdim_mock as ftdim
+
+    _has_funcdim = False
 
 from tensordict.base import (
     _ACCEPTED_CLASSES,
@@ -1561,7 +1569,11 @@ def _get_names_idx(self, idx):
         else:
 
             def is_boolean(idx):
-                from functorch import dim as ftdim
+                try:
+                    from functorch import dim as ftdim
+
+                except ImportError:
+                    from tensordict.utils import _ftdim_mock as ftdim
 
                 if isinstance(idx, ftdim.Dim):
                     return None

tensordict/nn/params.py

@@ -14,7 +14,15 @@
 from typing import Any, Callable, Iterator, OrderedDict, Sequence, Type
 
 import torch
-from functorch import dim as ftdim
+
+try:
+    from functorch import dim as ftdim
+
+    _has_funcdim = True
+except ImportError:
+    from tensordict.utils import _ftdim_mock as ftdim
+
+    _has_funcdim = False
 
 from tensordict._lazy import _CustomOpTensorDict, LazyStackedTensorDict
 from tensordict._td import _SubTensorDict, TensorDict

tensordict/utils.py

@@ -39,7 +39,13 @@
 
 import numpy as np
 import torch
-from functorch import dim as ftdim
+
+try:
+    from functorch import dim as ftdim
+
+    _has_funcdim = True
+except ImportError:
+    _has_funcdim = False
 from packaging.version import parse
 from tensordict._contextlib import _DecoratorContextManager
 from tensordict._tensordict import (  # noqa: F401
@@ -2207,3 +2213,16 @@ def is_non_tensor(data):
 
 def _is_non_tensor(cls: type):
     return getattr(cls, "_is_non_tensor", False)
+
+
+if not _has_funcdim:
+
+    class _ftdim_mock:
+        class Dim:
+            pass
+
+        class Tensor:
+            pass
+
+        def dims(self, *args, **kwargs):
+            raise ImportError("functorch.dim not found")

test/test_tensordict.py

@@ -29,7 +29,15 @@
     prod,
     TestTensorDictsBase,
 )
-from functorch import dim as ftdim
+
+try:
+    from functorch import dim as ftdim
+
+    _has_funcdim = True
+except ImportError:
+    from tensordict.utils import _ftdim_mock as ftdim
+
+    _has_funcdim = False
 
 from tensordict import LazyStackedTensorDict, make_tensordict, TensorDict
 from tensordict._lazy import _CustomOpTensorDict
@@ -7869,6 +7877,7 @@ def _pool_fixt():
         yield pool
 
 
+@pytest.mark.skipif(not _has_funcdim, reason="functorch.dim could not be found")
 class TestFCD(TestTensorDictsBase):
     """Test stack for first-class dimension."""