Bcast object wrappers, attempt 2

arraycontext/__init__.py

@@ -46,6 +46,7 @@
     serialize_container,
 )
 from .container.arithmetic import (
+    BcastUntilActxArray,
     with_container_arithmetic,
 )
 from .container.dataclass import dataclass_array_container
@@ -115,6 +116,7 @@
     "ArrayOrContainerOrScalarT",
     "ArrayOrContainerT",
     "ArrayT",
+    "BcastUntilActxArray",
     "CommonSubexpressionTag",
     "EagerJAXArrayContext",
     "ElementwiseMapKernelTag",

arraycontext/container/__init__.py

@@ -168,6 +168,8 @@ def __mul__(self, other: ArrayOrScalar | Self) -> Self: ...
     def __rmul__(self, other: ArrayOrScalar | Self) -> Self: ...
     def __truediv__(self, other: ArrayOrScalar | Self) -> Self: ...
     def __rtruediv__(self, other: ArrayOrScalar | Self) -> Self: ...
+    def __pow__(self, other: ArrayOrScalar | Self) -> Self: ...
+    def __rpow__(self, other: ArrayOrScalar | Self) -> Self: ...
 
 
 ArrayContainerT = TypeVar("ArrayContainerT", bound=ArrayContainer)

arraycontext/container/arithmetic.py

@@ -6,6 +6,8 @@
 .. currentmodule:: arraycontext
 
 .. autofunction:: with_container_arithmetic
+
+.. autoclass:: BcastUntilActxArray
 """
 
 
@@ -34,12 +36,23 @@
 """
 
 import enum
+import operator
 from collections.abc import Callable
+from dataclasses import dataclass, field
+from functools import partialmethod
+from numbers import Number
 from typing import Any, TypeVar
 from warnings import warn
 
 import numpy as np
 
+from arraycontext.container import (
+    NotAnArrayContainerError,
+    deserialize_container,
+    serialize_container,
+)
+from arraycontext.context import ArrayContext, ArrayOrContainer
+
 
 # {{{ with_container_arithmetic
 
@@ -142,8 +155,9 @@ def __instancecheck__(cls, instance: Any) -> bool:
             warn(
                  "Broadcasting container against non-object numpy array. "
                  "This was never documented to work and will now stop working in "
-                 "2025. Convert the array to an object array to preserve the "
-                 "current semantics.", DeprecationWarning, stacklevel=3)
+                 "2025. Convert the array to an object array or use "
+                 "arraycontext.BcastUntilActxArray (or similar) to obtain the desired "
+                 "broadcasting semantics.", DeprecationWarning, stacklevel=3)
             return True
         else:
             return False
@@ -207,6 +221,14 @@ class has an ``array_context`` attribute. If so, and if :data:`__debug__`
 
     Each operator class also includes the "reverse" operators if applicable.
 
+    .. note::
+
+        For the generated binary arithmetic operators, if certain types
+        should be broadcast over the container (with the container as the
+        'outer' structure) but are not handled in this way by their types,
+        you may wrap them in :class:`BcastUntilActxArray` to achieve
+        the desired semantics.
+
     .. note::
 
         To generate the code implementing the operators, this function relies on
@@ -402,8 +424,9 @@ def wrap(cls: Any) -> Any:
                 warn(
                     f"Broadcasting array context array types across {cls} "
                     "has been explicitly "
-                    "enabled. As of 2025, this will stop working. "
-                    "There is no replacement as of right now. "
+                    "enabled. As of 2026, this will stop working. "
+                    "Use arraycontext.Bcast* object wrappers for "
+                    "roughly equivalent functionality. "
                     "See the discussion in "
                     "https://github.com/inducer/arraycontext/pull/190. "
                     "To opt out now (and avoid this warning), "
@@ -413,8 +436,9 @@ def wrap(cls: Any) -> Any:
                 warn(
                     f"Broadcasting array context array types across {cls} "
                     "has been implicitly "
-                    "enabled. As of 2025, this will no longer work. "
-                    "There is no replacement as of right now. "
+                    "enabled. As of 2026, this will no longer work. "
+                    "Use arraycontext.Bcast* object wrappers for "
+                    "roughly equivalent functionality. "
                     "See the discussion in "
                     "https://github.com/inducer/arraycontext/pull/190. "
                     "To opt out now (and avoid this warning), "
@@ -603,8 +627,9 @@ def {fname}(arg1):
                             if isinstance(arg2, {tup_str(bcast_actx_ary_types)}):
                                 warn("Broadcasting {cls} over array "
                                     f"context array type {{type(arg2)}} is deprecated "
-                                    "and will no longer work in 2025. "
-                                    "There is no replacement as of right now. "
+                                    "and will no longer work in 2026. "
+                                    "Use arraycontext.Bcast* object wrappers for "
+                                    "roughly equivalent functionality. "
                                     "See the discussion in "
                                     "https://github.com/inducer/arraycontext/"
                                     "pull/190. ",
@@ -654,8 +679,10 @@ def {fname}(arg2, arg1):
                                         warn("Broadcasting {cls} over array "
                                             f"context array type {{type(arg1)}} "
                                             "is deprecated "
-                                            "and will no longer work in 2025."
-                                            "There is no replacement as of right now. "
+                                            "and will no longer work in 2026."
+                                            "Use arraycontext.Bcast* object "
+                                            "wrappers for roughly equivalent "
+                                            "functionality. "
                                             "See the discussion in "
                                             "https://github.com/inducer/arraycontext/"
                                             "pull/190. ",
@@ -687,4 +714,111 @@ def {fname}(arg2, arg1):
 # }}}
 
 
+# {{{ Bcast object-ified broadcast rules
+
+# Possible advantages of the "Bcast" broadcast-rule-as-object design:
+#
+# - If one rule does not fit the user's need, they can straightforwardly use
+#   another.
+#
+# - It's straightforward to find where certain broadcast rules are used.
+#
+# - The broadcast rule can contain more state. For example, it's now easy
+#   for the rule to know what array context should be used to determine
+#   actx array types.
+#
+# Possible downsides of the "Bcast" broadcast-rule-as-object design:
+#
+# - User code is a bit more wordy.
+
+@dataclass(frozen=True)
+class BcastUntilActxArray:
+    """
+    An operator-overloading wrapper around an object (*broadcastee*) that should be
+    broadcast across array containers until the 'opposite' operand is one of the
+    :attr:`~arraycontext.ArrayContext.array_types`
+    of *actx* or a :class:`~numbers.Number`.
+
+    Suggested usage pattern::
+
+        bcast = functools.partial(BcastUntilActxArray, actx)
+
+        container + bcast(actx_array)
+
+    .. automethod:: __init__
+    """
+
+    array_context: ArrayContext
+    broadcastee: ArrayOrContainer
+
+    _stop_types: tuple[type, ...] = field(init=False)
+
+    def __post_init__(self) -> None:
+        object.__setattr__(
+                self, "_stop_types", (*self.array_context.array_types, Number))
+
+    def _binary_op(self,
+                   op: Callable[
+                       [ArrayOrContainer, ArrayOrContainer],
+                       ArrayOrContainer
+                   ],
+                   right: ArrayOrContainer
+               ) -> ArrayOrContainer:
+        try:
+            serialized = serialize_container(right)
+        except NotAnArrayContainerError:
+            return op(self.broadcastee, right)
+
+        return deserialize_container(right, [
+            (k, op(self.broadcastee, right_v)
+                if isinstance(right_v, self._stop_types) else
+                self._binary_op(op, right_v)
+            )
+            for k, right_v in serialized])
+
+    def _rev_binary_op(self,
+                   op: Callable[
+                       [ArrayOrContainer, ArrayOrContainer],
+                       ArrayOrContainer
+                   ],
+                   left: ArrayOrContainer
+               ) -> ArrayOrContainer:
+        try:
+            serialized = serialize_container(left)
+        except NotAnArrayContainerError:
+            return op(left, self.broadcastee)
+
+        return deserialize_container(left, [
+            (k, op(left_v, self.broadcastee)
+                if isinstance(left_v, self._stop_types) else
+                self._rev_binary_op(op, left_v)
+            )
+            for k, left_v in serialized])
+
+    __add__ = partialmethod(_binary_op, operator.add)
+    __radd__ = partialmethod(_rev_binary_op, operator.add)
+    __sub__ = partialmethod(_binary_op, operator.sub)
+    __rsub__ = partialmethod(_rev_binary_op, operator.sub)
+    __mul__ = partialmethod(_binary_op, operator.mul)
+    __rmul__ = partialmethod(_rev_binary_op, operator.mul)
+    __truediv__ = partialmethod(_binary_op, operator.truediv)
+    __rtruediv__ = partialmethod(_rev_binary_op, operator.truediv)
+    __floordiv__ = partialmethod(_binary_op, operator.floordiv)
+    __rfloordiv__ = partialmethod(_rev_binary_op, operator.floordiv)
+    __mod__ = partialmethod(_binary_op, operator.mod)
+    __rmod__ = partialmethod(_rev_binary_op, operator.mod)
+    __pow__ = partialmethod(_binary_op, operator.pow)
+    __rpow__ = partialmethod(_rev_binary_op, operator.pow)
+
+    __lshift__ = partialmethod(_binary_op, operator.lshift)
+    __rlshift__ = partialmethod(_rev_binary_op, operator.lshift)
+    __rshift__ = partialmethod(_binary_op, operator.rshift)
+    __rrshift__ = partialmethod(_rev_binary_op, operator.rshift)
+    __and__ = partialmethod(_binary_op, operator.and_)
+    __rand__ = partialmethod(_rev_binary_op, operator.and_)
+    __or__ = partialmethod(_binary_op, operator.or_)
+    __ror__ = partialmethod(_rev_binary_op, operator.or_)
+
+# }}}
+
 # vim: foldmethod=marker

doc/conf.py

@@ -42,4 +42,5 @@
 
 nitpick_ignore_regex = [
     ["py:class", r"arraycontext\.context\.ContainerOrScalarT"],
+    ["py:class", r"ArrayOrContainer"],
     ]

test/test_arraycontext.py

@@ -34,6 +34,7 @@
 from pytools.tag import Tag
 
 from arraycontext import (
+    BcastUntilActxArray,
     EagerJAXArrayContext,
     NumpyArrayContext,
     PyOpenCLArrayContext,
@@ -1189,7 +1190,7 @@ def test_container_equality(actx_factory):
 # }}}
 
 
-# {{{ test_no_leaf_array_type_broadcasting
+# {{{ test_leaf_array_type_broadcasting
 
 def test_no_leaf_array_type_broadcasting(actx_factory):
     from testlib import Foo
@@ -1198,14 +1199,85 @@ def test_no_leaf_array_type_broadcasting(actx_factory):
 
     dof_ary = DOFArray(actx, (actx.np.zeros(3, dtype=np.float64) + 41, ))
     foo = Foo(dof_ary)
+    bar = foo + 4
+
+    bcast = partial(BcastUntilActxArray, actx)
 
     actx_ary = actx.from_numpy(4*np.ones((3, )))
     with pytest.raises(TypeError):
         foo + actx_ary
 
+    baz = foo + bcast(actx_ary)
+    qux = bcast(actx_ary) + foo
+
+    np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                               actx.to_numpy(baz.u[0]))
+
+    np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                               actx.to_numpy(qux.u[0]))
+
+    baz = foo + bcast(actx_ary)
+    qux = bcast(actx_ary) + foo
+
+    np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                               actx.to_numpy(baz.u[0]))
+
+    np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                               actx.to_numpy(qux.u[0]))
+
+    mc = MyContainer(
+         name="hi",
+         mass=dof_ary,
+         momentum=make_obj_array([dof_ary, dof_ary]),
+         enthalpy=dof_ary)
+
     with pytest.raises(TypeError):
-        foo + actx.from_numpy(np.array(4))
+        mc_op = mc + actx_ary
+
+    mom_op = mc.momentum + bcast(actx_ary)
+    np.testing.assert_allclose(45, actx.to_numpy(mom_op[0][0]))
+
+    mc_op = mc + bcast(actx_ary)
+    np.testing.assert_allclose(45, actx.to_numpy(mc_op.mass[0]))
+    np.testing.assert_allclose(45, actx.to_numpy(mc_op.momentum[1][0]))
+
+    mom_op = mc.momentum + bcast(actx_ary)
+    np.testing.assert_allclose(45, actx.to_numpy(mom_op[0][0]))
+
+    mc_op = mc + bcast(actx_ary)
+    np.testing.assert_allclose(45, actx.to_numpy(mc_op.mass[0]))
+    np.testing.assert_allclose(45, actx.to_numpy(mc_op.momentum[1][0]))
+
+    def _actx_allows_scalar_broadcast(actx):
+        if not isinstance(actx, PyOpenCLArrayContext):
+            return True
+        else:
+            import pyopencl as cl
+
+            # See https://github.com/inducer/pyopencl/issues/498
+            return cl.version.VERSION > (2021, 2, 5)
+
+    if _actx_allows_scalar_broadcast(actx):
+        with pytest.raises(TypeError):
+            foo + actx.from_numpy(np.array(4))
+
+        quuz = bcast(actx.from_numpy(np.array(4))) + foo
+        quux = foo + bcast(actx.from_numpy(np.array(4)))
+
+        np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                                   actx.to_numpy(quux.u[0]))
+
+        np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                                   actx.to_numpy(quuz.u[0]))
 
+        quuz = bcast(actx.from_numpy(np.array(4))) + foo
+        quux = foo + bcast(actx.from_numpy(np.array(4)))
+
+        np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                                   actx.to_numpy(quux.u[0]))
+
+        np.testing.assert_allclose(actx.to_numpy(bar.u[0]),
+                                   actx.to_numpy(quuz.u[0]))
 # }}}
 
 
@@ -1220,6 +1292,8 @@ def test_outer(actx_factory):
     b_ary_of_dofs = a_ary_of_dofs + 1
     b_bcast_dc_of_dofs = a_bcast_dc_of_dofs + 1
 
+    bcast = partial(BcastUntilActxArray, actx)
+
     from arraycontext import outer
 
     def equal(a, b):
@@ -1274,6 +1348,15 @@ def equal(a, b):
                 b_bcast_dc_of_dofs.momentum),
             enthalpy=a_bcast_dc_of_dofs.enthalpy*b_bcast_dc_of_dofs.enthalpy))
 
+    # Array context scalars
+    two = actx.from_numpy(np.array(2))
+    assert equal(
+        outer(bcast(two), b_bcast_dc_of_dofs),
+        bcast(two)*b_bcast_dc_of_dofs)
+    assert equal(
+        outer(a_bcast_dc_of_dofs, bcast(two)),
+        a_bcast_dc_of_dofs*bcast(two))
+
 # }}}