[dynamo][pytree][1/N] make CXX pytree traceable: tree_iter / tree_leaves (#137397)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/137397
Approved by: https://github.com/jansel
ghstack dependencies: #141360

test/dynamo/test_misc.py

@@ -32,7 +32,7 @@ import torch
 import torch._dynamo.testing
 import torch._inductor.test_case
 import torch.onnx.operators
-import torch.utils._pytree as pytree
+import torch.utils._pytree as python_pytree
 import torch.utils.cpp_extension
 from torch import Tensor
 from torch._C import FileCheck
@@ -89,9 +89,11 @@ from torch.testing._internal.jit_utils import JitTestCase
 from torch.testing._internal.logging_utils import logs_to_string
 
 
-HAS_OPTREE = importlib.util.find_spec("optree")
+HAS_OPTREE = python_pytree._cxx_pytree_exists
 if HAS_OPTREE:
-    import optree
+    import torch.utils._cxx_pytree as cxx_pytree
+else:
+    cxx_pytree = None
 
 MyTuple = collections.namedtuple("MyTuple", ["a", "b", "ab"])
 T = typing.TypeVar("T")
@@ -293,9 +295,9 @@ class MiscTests(torch._inductor.test_case.TestCase):
 
     @unittest.skipIf(not HAS_OPTREE, "missing optree package")
     def test_optree_graph_break_message(self):
-        @torch.compile(
+        import optree
-            backend="eager",
+
-        )
+        @torch.compile(backend="eager")
         def fn(x):
             d = {"a": 1}
             optree.tree_flatten(d)
@@ -8666,9 +8668,9 @@ def ___make_guard_fn():
 
     def test_tracing_py_tree(self):
         def fn(xs):
-            flat_xs, spec = pytree.tree_flatten(xs)
+            flat_xs, spec = python_pytree.tree_flatten(xs)
             res = [x.clone() for x in flat_xs]
-            return pytree.tree_unflatten(res, spec)
+            return python_pytree.tree_unflatten(res, spec)
 
         xs = [torch.tensor(i) for i in range(3)]
 
@@ -8678,12 +8680,10 @@ def ___make_guard_fn():
         self.assertEqual(counter.op_count, 3)
 
     def test_tracing_nested_py_tree(self):
-        import torch.utils._pytree as pytree
-
         def fn(xs):
-            flat_xs, spec = pytree.tree_flatten(xs)
+            flat_xs, spec = python_pytree.tree_flatten(xs)
             res = [x.clone() for x in flat_xs]
-            return pytree.tree_unflatten(res, spec)
+            return python_pytree.tree_unflatten(res, spec)
 
         xs = [torch.tensor(i) for i in range(3)]
         xsl = [xs, xs, xs, xs]
@@ -8696,12 +8696,10 @@ def ___make_guard_fn():
         self.assertEqual(counter.op_count, 12)
 
     def test_tracing_nested_py_tree_tuples(self):
-        import torch.utils._pytree as pytree
-
         def fn(xs):
-            flat_xs, spec = pytree.tree_flatten(xs)
+            flat_xs, spec = python_pytree.tree_flatten(xs)
             res = [x.clone() for x in flat_xs]
-            return pytree.tree_unflatten(res, spec)
+            return python_pytree.tree_unflatten(res, spec)
 
         xs = [torch.tensor(i) for i in range(3)]
         xsl = (xs, xs, xs, xs)
@@ -8714,12 +8712,10 @@ def ___make_guard_fn():
         self.assertEqual(counter.op_count, 12)
 
     def test_tracing_nested_py_tree_dicts(self):
-        import torch.utils._pytree as pytree
-
         def fn(xs):
-            flat_xs, spec = pytree.tree_flatten(xs)
+            flat_xs, spec = python_pytree.tree_flatten(xs)
             res = [x.clone() for x in flat_xs]
-            return pytree.tree_unflatten(res, spec)
+            return python_pytree.tree_unflatten(res, spec)
 
         xs = [torch.tensor(i) for i in range(3)]
         xsl = {
@@ -8752,12 +8748,10 @@ def ___make_guard_fn():
         self.assertEqual(counter.op_count, 2)
 
     def test_tracing_nested_py_tree_mixed_all(self):
-        import torch.utils._pytree as pytree
-
         def fn(xs):
-            flat_xs, spec = pytree.tree_flatten(xs)
+            flat_xs, spec = python_pytree.tree_flatten(xs)
             res = [x.clone() for x in flat_xs]
-            return pytree.tree_unflatten(res, spec)
+            return python_pytree.tree_unflatten(res, spec)
 
         xs = [torch.tensor(i) for i in range(3)]
         xsa = (xs, xs)
@@ -8802,13 +8796,12 @@ def ___make_guard_fn():
         self.assertEqual(cnt.frame_count, 2)
 
     def test_tracing_py_tree_tensor_subclass(self):
-        import torch.utils._pytree as pytree
         from torch.testing._internal.two_tensor import TwoTensor
         from torch.utils.checkpoint import checkpoint
 
         def fn(xs):
             nested_xs = [[xs]]
-            flat_xs, spec = pytree.tree_flatten(xs)
+            flat_xs, spec = python_pytree.tree_flatten(xs)
             return flat_xs[0].clone()
 
         # use checkpoint to trigger a "sourceless" tensor subclass
@@ -8823,13 +8816,11 @@ def ___make_guard_fn():
         self.assertEqual(counter.op_count, 2)
 
     def test_tracing_tree_map_only(self):
-        import torch.utils._pytree as pytree
-
         def fn(xs):
             def mapper(x):
                 return x.clone()
 
-            y = pytree.tree_map_only(torch.Tensor, mapper, xs)
+            y = python_pytree.tree_map_only(torch.Tensor, mapper, xs)
             return y
 
         xs = [torch.tensor(i) for i in range(3)] + ["hi"]
@@ -10183,7 +10174,9 @@ def ___make_guard_fn():
         self.assertEqual(actual, expected)
 
     def test_pytree_tree_leaves(self):
-        implemtations = [("python", pytree)]
+        implemtations = [("python", python_pytree)]
+        if cxx_pytree is not None:
+            implemtations.append(("cxx", cxx_pytree))
 
         for name, module in implemtations:
             with self.subTest(f"pytree implement: {name}"):
@@ -10215,7 +10208,7 @@ def ___make_guard_fn():
                 self.assertEqual(actual, expected)
 
     def test_pytree_tree_flatten_unflatten(self):
-        implemtations = [("python", pytree)]
+        implemtations = [("python", python_pytree)]
 
         for name, module in implemtations:
             with self.subTest(f"pytree implement: {name}"):
@@ -10264,7 +10257,7 @@ def ___make_guard_fn():
             self.assertEqual(actual, expected)
 
     def test_pytree_tree_map(self):
-        implemtations = [("python", pytree)]
+        implemtations = [("python", python_pytree)]
 
         for name, module in implemtations:
             with self.subTest(f"pytree implement: {name}"):

torch/_dynamo/guards.py

@@ -2080,10 +2080,11 @@ class GuardBuilder(GuardBuilderBase):
         obj_ref = None
         # Not necessary to have weakref for Enum type, but there is a bug that
         # makes hasattr(guarded_object.__class__, "__weakref__") return True.
+        supports_weakref = (
+            getattr(guarded_object.__class__, "__weakrefoffset__", 0) != 0
+        )
         # See D64140537 for why we are checking for tuple.
-        if hasattr(guarded_object.__class__, "__weakref__") and not isinstance(
+        if supports_weakref and not isinstance(guarded_object, (enum.Enum, tuple)):
-            guarded_object, (enum.Enum, tuple)
-        ):
             obj_ref = weakref.ref(guarded_object)
 
         guard.set_export_info(

torch/_dynamo/polyfills/__init__.py

@@ -23,6 +23,7 @@ if TYPE_CHECKING:
         itertools as itertools,
         operator as operator,
         os as os,
+        pytree as pytree,
         sys as sys,
     )
 

torch/_dynamo/polyfills/loader.py

@@ -18,6 +18,7 @@ POLYFILLED_MODULE_NAMES: Tuple[str, ...] = (
     "itertools",
     "operator",
     "os",
+    "pytree",
     "sys",
 )
 POLYFILLED_MODULES: Tuple["ModuleType", ...] = tuple(

torch/_dynamo/polyfills/pytree.py

@@ -0,0 +1,89 @@
+"""
+Python polyfills for torch.utils.pytree
+"""
+
+from __future__ import annotations
+
+from typing import Any, Callable, Iterable, TYPE_CHECKING
+
+import torch.utils._pytree as python_pytree
+
+from ..decorators import substitute_in_graph
+
+
+if TYPE_CHECKING:
+    from torch.utils._cxx_pytree import PyTree
+
+
+__all__: list[str] = []
+
+
+if python_pytree._cxx_pytree_exists:
+    import optree
+    import optree._C
+
+    import torch.utils._cxx_pytree as cxx_pytree
+
+    @substitute_in_graph(
+        optree._C.is_dict_insertion_ordered,
+        can_constant_fold_through=True,
+    )
+    def _(*args: Any, **kwargs: Any) -> bool:
+        # In namespace 'torch', the dictionary is always traversed in insertion order.
+        # This function returns True.
+        raise ValueError(
+            "Should not be called directly "
+            "because the original function will be called in the constant fold path."
+        )
+
+    __name = ""
+    for __name in (
+        "is_namedtuple",
+        "is_namedtuple_class",
+        "is_namedtuple_instance",
+        "is_structseq",
+        "is_structseq_class",
+        "is_structseq_instance",
+        "namedtuple_fields",
+        "structseq_fields",
+    ):
+        __func = getattr(optree, __name)
+        substitute_in_graph(__func, can_constant_fold_through=True)(
+            __func.__python_implementation__
+        )
+        del __func
+    del __name
+
+    @substitute_in_graph(cxx_pytree.tree_iter, can_constant_fold_through=False)
+    def tree_iter(
+        tree: PyTree,
+        is_leaf: Callable[[PyTree], bool] | None = None,
+    ) -> Iterable[Any]:
+        stack = [tree]
+        while stack:
+            node = stack.pop()
+            if node is None or (is_leaf is not None and is_leaf(node)):
+                yield node
+                continue
+            if optree.register_pytree_node.get(type(node), namespace="torch") is None:  # type: ignore[attr-defined]
+                yield node
+                continue
+
+            children, *_ = optree.tree_flatten_one_level(
+                node,
+                is_leaf=is_leaf,
+                none_is_leaf=True,
+                namespace="torch",
+            )
+            stack.extend(reversed(children))
+
+    __all__ += ["tree_iter"]
+
+    @substitute_in_graph(cxx_pytree.tree_leaves, can_constant_fold_through=True)
+    def tree_leaves(
+        tree: PyTree,
+        is_leaf: Callable[[PyTree], bool] | None = None,
+    ) -> list[Any]:
+        return list(tree_iter(tree, is_leaf=is_leaf))
+
+    __all__ += ["tree_leaves"]

torch/_dynamo/trace_rules.py

@@ -3310,6 +3310,7 @@ MOD_INLINELIST = [
     "torch.testing",
     "torch.utils._content_store",
     "torch.utils._contextlib",
+    "torch.utils._cxx_pytree",
     "torch.utils._device",
     "torch.utils._foreach_utils",
     "torch.utils._python_dispatch",

torch/utils/_cxx_pytree.py

@@ -30,10 +30,10 @@ from typing import (
 from typing_extensions import deprecated
 
 import optree
-from optree import PyTreeSpec  # direct import for type annotations
+from optree import PyTreeSpec as TreeSpec  # direct import for type annotations
 
-import torch.utils._pytree as _pytree
+import torch.utils._pytree as python_pytree
-from torch.utils._pytree import KeyEntry
+from torch.utils._pytree import KeyEntry as KeyEntry
 
 
 __all__ = [
@@ -79,7 +79,6 @@ R = TypeVar("R")
 
 Context = Any
 PyTree = Any
-TreeSpec = PyTreeSpec
 FlattenFunc = Callable[[PyTree], Tuple[List[Any], Context]]
 UnflattenFunc = Callable[[Iterable[Any], Context], PyTree]
 OpTreeUnflattenFunc = Callable[[Context, Iterable[Any]], PyTree]
@@ -151,9 +150,7 @@ def register_pytree_node(
         from_dumpable_context=from_dumpable_context,
     )
 
-    from . import _pytree as python
+    python_pytree._private_register_pytree_node(
-
-    python._private_register_pytree_node(
         cls,
         flatten_fn,
         unflatten_fn,
@@ -871,24 +868,19 @@ def treespec_dumps(treespec: TreeSpec, protocol: Optional[int] = None) -> str:
             f"treespec_dumps(spec): Expected `spec` to be instance of "
             f"TreeSpec but got item of type {type(treespec)}."
         )
-    from ._pytree import (
-        tree_structure as _tree_structure,
-        treespec_dumps as _treespec_dumps,
-    )
 
-    orig_treespec = _tree_structure(tree_unflatten([0] * treespec.num_leaves, treespec))
+    dummy_tree = tree_unflatten([0] * treespec.num_leaves, treespec)
-    return _treespec_dumps(orig_treespec, protocol=protocol)
+    orig_treespec = python_pytree.tree_structure(dummy_tree)
+    return python_pytree.treespec_dumps(orig_treespec, protocol=protocol)
 
 
 def treespec_loads(serialized: str) -> TreeSpec:
     """Deserialize a treespec from a JSON string."""
-    from ._pytree import (
+    orig_treespec = python_pytree.treespec_loads(serialized)
-        tree_unflatten as _tree_unflatten,
+    dummy_tree = python_pytree.tree_unflatten(
-        treespec_loads as _treespec_loads,
+        [0] * orig_treespec.num_leaves,
+        orig_treespec,
     )
-
-    orig_treespec = _treespec_loads(serialized)
-    dummy_tree = _tree_unflatten([0] * orig_treespec.num_leaves, orig_treespec)
     treespec = tree_structure(dummy_tree)
     return treespec
 
@@ -1002,6 +994,10 @@ def key_get(obj: Any, kp: KeyPath) -> Any:
     raise NotImplementedError("KeyPaths are not yet supported in cxx_pytree.")
 
 
-_pytree._cxx_pytree_imported = True
+with python_pytree._NODE_REGISTRY_LOCK:
-for args, kwargs in _pytree._cxx_pytree_pending_imports:
+    python_pytree._cxx_pytree_imported = True
+    args, kwargs = (), {}  # type: ignore[var-annotated]
+    for args, kwargs in python_pytree._cxx_pytree_pending_imports:
         _private_register_pytree_node(*args, **kwargs)
+    python_pytree._cxx_pytree_pending_imports.clear()
+    del args, kwargs