[nnx] support pure dicts

examples/nnx_toy_examples/02_lifted_transforms.py

@@ -86,6 +86,7 @@ def test_step(model: MLP, batch):
 total_steps = 10_000
 for step, batch in enumerate(dataset(32)):
   train_step(model, optimizer, batch)
+  print(nnx.graph.GRAPH_CONTEXT)
 
   if step % 1000 == 0:
     logs = test_step(model, (X, Y))

flax/nnx/filterlib.py

@@ -65,12 +65,21 @@ def filters_to_predicates(filters: tuple[Filter, ...]) -> tuple[Predicate, ...]:
         )
   return tuple(map(to_predicate, filters))
 
+
+class HasTag(tp.Protocol):
+  tag: str
+
+
+def _has_tag(x: tp.Any) -> tp.TypeGuard[HasTag]:
+  return hasattr(x, 'tag')
+
+
 @dataclasses.dataclass(frozen=True)
 class WithTag:
   tag: str
 
   def __call__(self, path: PathParts, x: tp.Any):
-    return hasattr(x, 'tag') and x.tag == self.tag
+    return _has_tag(x) and x.tag == self.tag
 
   def __repr__(self):
     return f'WithTag({self.tag!r})'

flax/nnx/graph.py

@@ -34,7 +34,7 @@
 from flax.nnx.statelib import FlatState, State
 from flax.nnx import variablelib
 from flax.nnx.variablelib import Variable, VariableState
-from flax.typing import Key, PathParts
+from flax.typing import Key, PathParts, is_key_like
 
 A = tp.TypeVar('A')
 B = tp.TypeVar('B')
@@ -43,6 +43,7 @@
 
 HA = tp.TypeVar('HA', bound=tp.Hashable)
 HB = tp.TypeVar('HB', bound=tp.Hashable)
+KeyT = tp.TypeVar('KeyT', bound=Key)
 
 Index = int
 Names = tp.Sequence[int]
@@ -241,6 +242,35 @@ def __treescope_repr__(self, path, subtree_renderer):
 
 jax.tree_util.register_static(NodeRef)
 
+@dataclasses.dataclass(frozen=True, repr=False)
+class VariableDef(reprlib.Representable):
+  type: type[Variable]
+  index: int
+  metadata: FrozenDict[str, tp.Any]
+
+  def __nnx_repr__(self):
+    yield reprlib.Object(type=type(self))
+    yield reprlib.Attr('type', self.type.__name__)
+    yield reprlib.Attr('index', self.index)
+    yield reprlib.Attr('metadata', reprlib.PrettyMapping(self.metadata))
+
+  def __treescope_repr__(self, path, subtree_renderer):
+    import treescope  # type: ignore[import-not-found,import-untyped]
+
+    return treescope.repr_lib.render_object_constructor(
+      object_type=type(self),
+      attributes={
+        'type': self.type,
+        'index': self.index,
+        'metadata': self.metadata,
+      },
+      path=path,
+      subtree_renderer=subtree_renderer,
+    )
+
+
+jax.tree_util.register_static(VariableDef)
+
 
 @dataclasses.dataclass(frozen=True, repr=False)
 class NodeDef(GraphDef[Node], reprlib.Representable):
@@ -253,7 +283,7 @@ class NodeDef(GraphDef[Node], reprlib.Representable):
   attributes: tuple[Key, ...]
   subgraphs: _HashableMapping[Key, NodeDef[tp.Any] | NodeRef[tp.Any]]
   static_fields: _HashableMapping[Key, tp.Any]
-  leaves: _HashableMapping[Key, NodeRef[tp.Any] | None]
+  leaves: _HashableMapping[Key, VariableDef | NodeRef[tp.Any]]
   metadata: tp.Any
   index_mapping: FrozenDict[Index, Index] | None
 
@@ -265,7 +295,7 @@ def create(
     attributes: tuple[Key, ...],
     subgraphs: tp.Iterable[tuple[Key, NodeDef[tp.Any] | NodeRef[tp.Any]]],
     static_fields: tp.Iterable[tuple[Key, tp.Any]],
-    leaves: tp.Iterable[tuple[Key, NodeRef[tp.Any] | None]],
+    leaves: tp.Iterable[tuple[Key, VariableDef | NodeRef[tp.Any]]],
     metadata: tp.Any,
     index_mapping: tp.Mapping[Index, Index] | None,
   ):
@@ -380,7 +410,7 @@ def _graph_flatten(
 
   subgraphs: list[tuple[Key, NodeDef[Node] | NodeRef]] = []
   static_fields: list[tuple[Key, tp.Any]] = []
-  leaves: list[tuple[Key, NodeRef | None]] = []
+  leaves: list[tuple[Key, VariableDef | NodeRef]] = []
 
   values, metadata = node_impl.flatten(node)
   for key, value in values:
@@ -393,10 +423,10 @@ def _graph_flatten(
       else:
         flat_state[(*path, key)] = value.to_state()
         variable_index = ref_index[value] = len(ref_index)
-        leaves.append((key, NodeRef(type(value), variable_index)))
-    elif is_state_leaf(value):
-      flat_state[(*path, key)] = value
-      leaves.append((key, None))
+        variabledef = VariableDef(
+          type(value), variable_index, FrozenDict(value.get_metadata())
+        )
+        leaves.append((key, variabledef))
     else:
       if isinstance(value, (jax.Array, np.ndarray)):
         path_str = '/'.join(map(str, (*path, key)))
@@ -420,7 +450,7 @@ def _graph_flatten(
 
 def unflatten(
   graphdef: GraphDef[Node],
-  state: GraphState,
+  state: tp.Mapping[KeyT, StateLeaf | tp.Mapping[Key, tp.Any]],
   /,
   *,
   index_ref: dict[Index, tp.Any] | None = None,
@@ -441,12 +471,12 @@ def unflatten(
       existing graph nodes are mutated to have the new content/topology
       specified by the graphdef.
   """
+  if isinstance(state, State):
+    state = state.raw_mapping
   if index_ref is None:
     index_ref = {}
   assert isinstance(graphdef, (NodeDef, NodeRef))
-  node = _graph_unflatten(
-    graphdef, state.raw_mapping, index_ref, index_ref_cache
-  )
+  node = _graph_unflatten(graphdef, state, index_ref, index_ref_cache)
   return node
 
 def _graph_unflatten(
@@ -480,7 +510,7 @@ def _graph_unflatten(
   node_impl = get_node_impl_for_type(nodedef.type)
 
   def _get_children():
-    children: dict[Key, StateLeaf | Node] = {}
+    children: dict[Key, NodeLeaf | Node] = {}
 
     # NOTE: we could allw adding new StateLeafs here
     if unkown_keys := set(state) - set(nodedef.attributes):
@@ -491,13 +521,13 @@ def _get_children():
     #  - (3) the key can be a subgraph, a leaf, or a static attribute
     for key in nodedef.attributes:
       if key not in state:
-        # TODO(cgarcia): maybe we shouldn't support unflattening with missing keys?
         # if key is not present create an empty types
         if key in nodedef.static_fields:
           children[key] = nodedef.static_fields[key]
         elif key in nodedef.subgraphs:
           # if the key is a subgraph we create an empty node
           subgraphdef = nodedef.subgraphs[key]
+          assert not isinstance(subgraphdef, VariableDef)
           if isinstance(subgraphdef, NodeRef):
             # subgraph exists, take it from the cache
             children[key] = index_ref[subgraphdef.index]
@@ -511,10 +541,10 @@ def _get_children():
               subgraphdef, substate, index_ref, index_ref_cache
             )
         elif key in nodedef.leaves:
-          noderef = nodedef.leaves[key]
-          if noderef is not None and noderef.index in index_ref:
+          variabledef = nodedef.leaves[key]
+          if variabledef.index in index_ref:
             # variable exists, take it from the cache
-            children[key] = index_ref[noderef.index]
+            children[key] = index_ref[variabledef.index]
           else:
             # key for a variable is missing, raise an error
             raise ValueError(
@@ -546,41 +576,47 @@ def _get_children():
             )
 
         elif key in nodedef.leaves:
-          if not is_state_leaf(value):
-            raise ValueError(f'Expected a leaf for {key!r}, but got {value!r}')
-
-          noderef = nodedef.leaves[key]
-
-          if noderef is None:
-            # if the leaf is None, it means that the value was originally
-            # a non-VariableState leaf, however we allow providing a
-            # VariableState presumbly created by modifying the State
-            if isinstance(value, VariableState):
-              value = value.to_variable()
-            children[key] = value
-          elif noderef.index in index_ref:
+          # if not is_state_leaf(value):
+          #   raise ValueError(f'Expected a leaf for {key!r}, but got {value!r}')
+
+          variabledef = nodedef.leaves[key]
+
+          if variabledef.index in index_ref:
             # add an existing variable
-            children[key] = index_ref[noderef.index]
+            assert isinstance(variabledef, NodeRef)
+            children[key] = index_ref[variabledef.index]
           else:
             # its a unseen variable, create a new one
-            if not isinstance(value, VariableState):
-              raise ValueError(
-                f'Expected a Variable type for {key!r}, but got {type(value)}.'
-              )
+            assert isinstance(variabledef, VariableDef)
+            # if not isinstance(value, VariableState):
+            #   raise ValueError(
+            #     f'Expected a Variable type for {key!r}, but got {type(value)}.'
+            #   )
             # when idxmap is present, check if the Varable exists there
             # and update existing variables if it does
-            if index_ref_cache is not None and noderef.index in index_ref_cache:
-              variable = index_ref_cache[noderef.index]
+            if (
+              index_ref_cache is not None
+              and variabledef.index in index_ref_cache
+            ):
+              # if variable exists, update it
+              variable = index_ref_cache[variabledef.index]
               if not isinstance(variable, Variable):
                 raise ValueError(
                   f'Expected a Variable type for {key!r}, but got {type(variable)}.'
                 )
-              variable.update_from_state(value)
+              if isinstance(value, VariableState):
+                variable.update_from_state(value)
+              else:
+                variable.raw_value = value
             else:  # if it doesn't, create a new variable
-              assert isinstance(value, VariableState)
-              variable = value.to_variable()
+              if isinstance(value, VariableState):
+                variable = value.to_variable()
+              else:
+                variable = variabledef.type.from_metadata(
+                  value, variabledef.metadata
+                )
             children[key] = variable
-            index_ref[noderef.index] = variable
+            index_ref[variabledef.index] = variable
         else:
           raise RuntimeError(f'Unknown key: {key!r}, this is a bug.')
 
@@ -676,7 +712,7 @@ def _graph_pop(
       pass
 
 
-def _graph_update_dynamic(node: tp.Any, state: tp.Mapping[Key, tp.Any]):
+def _graph_update_dynamic(node: tp.Any, state: tp.Mapping[KeyT, tp.Any]):
   if not is_node(node):
     raise RuntimeError(f'Unsupported type: {type(node)}')
 
@@ -1251,12 +1287,11 @@ def split(
   states = _split_state(state, filters)
   return graphdef, *states
 
-
 def merge(
   graphdef: GraphDef[A],
-  state: GraphState,
+  state: tp.Mapping[KeyT, tp.Any],
   /,
-  *states: GraphState,
+  *states: tp.Mapping[KeyT, tp.Any],
 ) -> A:
   """The inverse of :func:`split`.
 
@@ -1293,13 +1328,15 @@ def merge(
   Returns:
     The merged :class:`Module`.
   """
-  state = GraphState.merge(state, *states)
+  state = State.merge(state, *states)
   node = unflatten(graphdef, state)
   return node
 
 
-def update(node, state: State, /, *states: State) -> None:
-  """Update the given graph node with a new :class:`State` in-place.
+def update(
+  node, state: tp.Mapping[KeyT, tp.Any], /, *states: tp.Mapping[KeyT, tp.Any]
+) -> None:
+  """Update the given graph node with a new state(s) in-place.
 
   Example usage::
 
@@ -1325,9 +1362,10 @@ def update(node, state: State, /, *states: State) -> None:
     *states: Additional :class:`State` objects.
   """
   if states:
-    state = GraphState.merge(state, *states)
-
-  _graph_update_dynamic(node, state.raw_mapping)
+    state = State.merge(state, *states)
+  if isinstance(state, State):
+    state = state.raw_mapping
+  _graph_update_dynamic(node, state)
 
 def _variables_generator(node) -> tp.Iterable[tuple[PathParts, Variable]]:
   for path, value in iter_graph(node):
@@ -1722,7 +1760,7 @@ def _key_path_to_key(key: tp.Any) -> Key:
   elif isinstance(
     key, (jax.tree_util.DictKey, jax.tree_util.FlattenedIndexKey)
   ):
-    if not isinstance(key.key, Key):
+    if not is_key_like(key.key):
       raise ValueError(
         f'Invalid key: {key.key}. May be due to its type not being hashable or comparable.'
       )

flax/nnx/spmd.py

@@ -31,19 +31,26 @@
 F = tp.TypeVar('F', bound=tp.Callable[..., tp.Any])
 PARTITION_NAME = 'partition_name'
 
+class HasSharding(tp.Protocol):
+  sharding: tuple[str | None, ...] | None
 
-def add_axis(tree: A, index: int, params: tp.Mapping[tp.Any, tp.Any]) -> A:
+
+def _has_sharding(x: tp.Any) -> tp.TypeGuard[HasSharding]:
+  return hasattr(x, 'sharding') and x.sharding is not None
+
+def add_axis(tree: A, index: int, params: tp.Mapping) -> A:
   axis_name = _get_partition_name(params)
 
   def _add_axis(x: tp.Any):
     if isinstance(x, variablelib.VariableState):
-      if hasattr(x, 'sharding') and x.sharding is not None:
+      if _has_sharding(x) and x.sharding is not None:
         sharding: list[str | None] = list(x.sharding)
         while len(sharding) < index:
           sharding.append(None)
         sharding.insert(index, axis_name)
         x.sharding = tuple(sharding)  # type: ignore
 
+      assert isinstance(x, variablelib.VariableState)
       x.add_axis(index, axis_name)
     return x
 

flax/nnx/statelib.py

@@ -320,7 +320,9 @@ def filter(
     return states  # type: ignore[bad-return-type]
 
   @staticmethod
-  def merge(state: State[K, V], /, *states: State[K, V]) -> State[K, V]:
+  def merge(
+    state: tp.Mapping[K, V], /, *states: tp.Mapping[K, V]
+  ) -> State[K, V]:
     """The inverse of :meth:`split() <flax.nnx.State.state.split>`.
 
     ``merge`` takes one or more ``State``'s and creates
@@ -353,14 +355,16 @@ def merge(state: State[K, V], /, *states: State[K, V]) -> State[K, V]:
       The merged ``State``.
     """
     if not states:
-      return state
+      if isinstance(state, State):
+        return state
+      return State(state)
 
     states = (state, *states)
 
     new_state: FlatState[V] = {}
 
     for state in states:
-      new_state.update(state.flat_state())  # type: ignore[attribute-error] # pytype is wrong here
+      new_state.update(traversals.flatten_mapping(state))  # type: ignore[attribute-error] # pytype is wrong here
 
     return State.from_flat_path(new_state)