Initial pickle and deepcopy singleton support

jax/_src/core.py

@@ -364,21 +364,55 @@ def __repr__(self):
 
 Atom = Union[Var, Literal]
 
+# Table that stores all primitive definitions.
+# Needed so that primitives are treated as singletons
+# when using cloudpickle.
+# Mapping type: (namespace, name) -> Primitive
+_PRIMITIVES_TABLE_: dict[tuple[str, str], Primitive] = {}
+
+def primitives_table_get(namespace: str, name: str):
+  if (namespace, name) in _PRIMITIVES_TABLE_:
+    return _PRIMITIVES_TABLE_[(namespace, name)]
+  raise NotImplementedError(
+    f"Op {(namespace, name)} not found in primitives table. (Did you import it yet?)."
+    f"Primitive table has {list(_PRIMITIVES_TABLE_.keys())}")
+
+def primitives_table_set(namespace: str, name: str, primitive: Primitive):
+  assert (namespace, name) not in _PRIMITIVES_TABLE_, (
+    f"The op name {(namespace, name)} is already taken. "
+    "Try changing the namespace with Primitive(..., namespace='<YOUR_PROJECT_NAME>')."
+  )
+  _PRIMITIVES_TABLE_[(namespace, name)] = primitive
+
+
 class Primitive:
+  # used to identify primitive singletons.
   name: str
+  namespace: str
   # set for multi-output primitives.
   multiple_results: bool = False
   # set for call primitives processed in final style.
   call_primitive: bool = False
   # set for map primitives processed in final style.
   map_primitive: bool = False
 
-  def __init__(self, name: str):
+  def __init__(self, name: str, namespace: str="__jax_core__"):
     self.name = name
+    self.namespace = namespace
+    primitives_table_set(namespace, name, self)
 
   def __repr__(self):
     return f'{self.name}'
 
+  def __reduce_ex__(self, __protocol) -> str | tuple[Any, ...]:
+    return primitives_table_get, (self.namespace, self.name)
+
+  def __deepcopy__(self, memo):
+    # Primitives are singletons, so copying is the same
+    # as returning self.
+    memo[id(self)] = self
+    return self
+
   def bind(self, *args, **params):
     assert (not config.enable_checks.value or
             all(isinstance(arg, Tracer) or valid_jaxtype(arg) for arg in args)), args

jax/_src/source_info_util.py

@@ -21,7 +21,7 @@
 import sysconfig
 import threading
 import types
-from typing import Optional, NamedTuple, Union
+from typing import Any, Optional, NamedTuple, Union
 
 import jax.version
 from jax._src.lib import xla_client
@@ -132,6 +132,10 @@ def replace(self, *, traceback: Optional[Traceback] = None,
         self.name_stack if name_stack is None else name_stack
     )
 
+  def __reduce_ex__(self, __protocol) -> str | tuple[Any, ...]:
+    # Dropping Traceback for now as it is not easy to pickle.
+    return SourceInfo, (None, self.name_stack)
+
 def new_source_info() -> SourceInfo:
   return SourceInfo(None, NameStack())
 

tests/copying_test.py

@@ -0,0 +1,24 @@
+from cloudpickle import cloudpickle
+from copy import deepcopy
+
+import jax
+from jax._src.core import jaxpr_as_fun
+
+def test_jaxpr_cloudpickle():
+  def f(a, b):
+    return a + b, b * a
+
+  jxpr = jax.make_jaxpr(f)(1, 2)
+  encoded = cloudpickle.dumps(jxpr)
+  loaded_jxpr = cloudpickle.loads(encoded)
+
+  assert jaxpr_as_fun(loaded_jxpr)(5, 3) == [8, 15]
+
+def test_jaxpr_deepcopy():
+  def f(a, b):
+    return b * a, a + b,
+
+  jxpr = jax.make_jaxpr(f)(1, 2)
+  copied_jaxpr = deepcopy(jxpr)
+
+  assert jaxpr_as_fun(copied_jaxpr)(5, 3) == [15, 8]