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from collections import namedtuple
from typing import Any, Callable, Dict, List, NamedTuple, Optional, Tuple, Type
import torch.return_types
from torch.utils._pytree import PyTree, TreeSpec
FlattenFuncSpec = Callable[[PyTree, TreeSpec], List]
FlattenFuncExactMatchSpec = Callable[[PyTree, TreeSpec], bool]
SUPPORTED_NODES: Dict[Type[Any], FlattenFuncSpec] = {}
SUPPORTED_NODES_EXACT_MATCH: Dict[Type[Any], Optional[FlattenFuncExactMatchSpec]] = {}
def register_pytree_flatten_spec(
cls: Type[Any],
flatten_fn_spec: FlattenFuncSpec,
flatten_fn_exact_match_spec: Optional[FlattenFuncExactMatchSpec] = None,
) -> None:
SUPPORTED_NODES[cls] = flatten_fn_spec
SUPPORTED_NODES_EXACT_MATCH[cls] = flatten_fn_exact_match_spec
def tree_flatten_spec(
pytree: PyTree,
spec: TreeSpec,
exact_structural_match=False,
) -> List[Any]:
if spec.is_leaf():
return [pytree]
if spec.type not in SUPPORTED_NODES:
raise RuntimeError(
f"{type(pytree)} does not have a flatten_fn_spec associated with it. Please register one with "
"torch.fx._pytree.register_pytree_flatten_spec. If you have serialized your model, make "
"sure that any custom pytrees have been registered before loading it.",
)
flatten_fn_spec = SUPPORTED_NODES[spec.type]
child_pytrees = flatten_fn_spec(pytree, spec)
if exact_structural_match:
flatten_fn_exact_match_spec = SUPPORTED_NODES_EXACT_MATCH[spec.type]
if flatten_fn_exact_match_spec and not flatten_fn_exact_match_spec(
pytree,
spec,
):
raise RuntimeError(f"Cannot flatten pytree {pytree}, given spec: {spec}")
result = []
for child, child_spec in zip(child_pytrees, spec.children_specs):
flat = tree_flatten_spec(child, child_spec, exact_structural_match)
result += flat
return result
def _dict_flatten_spec(d: Dict[Any, Any], spec: TreeSpec) -> List[Any]:
return [d[k] for k in spec.context]
def _list_flatten_spec(d: List[Any], spec: TreeSpec) -> List[Any]:
return [d[i] for i in range(spec.num_children)]
def _tuple_flatten_spec(d: Tuple[Any], spec: TreeSpec) -> List[Any]:
return [d[i] for i in range(spec.num_children)]
def _namedtuple_flatten_spec(d: NamedTuple, spec: TreeSpec) -> List[Any]:
return [d[i] for i in range(spec.num_children)]
def _dict_flatten_spec_exact_match(d: Dict[Any, Any], spec: TreeSpec) -> bool:
return len(d) == spec.num_children
def _list_flatten_spec_exact_match(d: List[Any], spec: TreeSpec) -> bool:
return len(d) == spec.num_children
def _tuple_flatten_spec_exact_match(d: Tuple[Any], spec: TreeSpec) -> bool:
return len(d) == spec.num_children
def _namedtuple_flatten_spec_exact_match(d: NamedTuple, spec: TreeSpec) -> bool:
return len(d) == spec.num_children
register_pytree_flatten_spec(dict, _dict_flatten_spec, _dict_flatten_spec_exact_match)
register_pytree_flatten_spec(list, _list_flatten_spec, _list_flatten_spec_exact_match)
register_pytree_flatten_spec(
tuple,
_tuple_flatten_spec,
_tuple_flatten_spec_exact_match,
)
for return_type in torch.return_types.all_return_types:
register_pytree_flatten_spec(
return_type,
_tuple_flatten_spec,
_tuple_flatten_spec_exact_match,
)
register_pytree_flatten_spec(
namedtuple, # type: ignore[arg-type]
_namedtuple_flatten_spec,
_namedtuple_flatten_spec_exact_match,
)