Re-enable passing dims alongside shape or size (#5325)

* Remove unused return value from helper functions
* Restore support for passing `dims` alongside `shape` or `size`
* Extract RV creation and `resize_shape` determination code

Closes #4656

pymc/distributions/distribution.py

@@ -19,12 +19,14 @@
 
 from abc import ABCMeta
 from functools import singledispatch
-from typing import Callable, Iterable, Optional, Sequence
+from typing import Callable, Iterable, Optional, Sequence, Tuple, Union
 
 import aesara
+import numpy as np
 
 from aeppl.logprob import _logcdf, _logprob
 from aesara import tensor as at
+from aesara.graph.basic import Variable
 from aesara.tensor.basic import as_tensor_variable
 from aesara.tensor.elemwise import Elemwise
 from aesara.tensor.random.op import RandomVariable
@@ -36,6 +38,8 @@
     Dims,
     Shape,
     Size,
+    StrongShape,
+    WeakDims,
     convert_dims,
     convert_shape,
     convert_size,
@@ -133,6 +137,37 @@ def fn(*args, **kwargs):
     return fn
 
 
+def _make_rv_and_resize_shape(
+    *,
+    cls,
+    dims: Optional[Dims],
+    model,
+    observed,
+    args,
+    **kwargs,
+) -> Tuple[Variable, Optional[WeakDims], Optional[Union[np.ndarray, Variable]], StrongShape]:
+    """Creates the RV and processes dims or observed to determine a resize shape."""
+    # Create the RV without dims information, because that's not something tracked at the Aesara level.
+    # If necessary we'll later replicate to a different size implied by already known dims.
+    rv_out = cls.dist(*args, **kwargs)
+    ndim_actual = rv_out.ndim
+    resize_shape = None
+
+    # # `dims` are only available with this API, because `.dist()` can be used
+    # # without a modelcontext and dims are not tracked at the Aesara level.
+    dims = convert_dims(dims)
+    dims_can_resize = kwargs.get("shape", None) is None and kwargs.get("size", None) is None
+    if dims is not None:
+        if dims_can_resize:
+            resize_shape, dims = resize_from_dims(dims, ndim_actual, model)
+        elif Ellipsis in dims:
+            # Replace ... with None entries to match the actual dimensionality.
+            dims = (*dims[:-1], *[None] * ndim_actual)[:ndim_actual]
+    elif observed is not None:
+        resize_shape, observed = resize_from_observed(observed, ndim_actual)
+    return rv_out, dims, observed, resize_shape
+
+
 class Distribution(metaclass=DistributionMeta):
     """Statistical distribution"""
 
@@ -213,28 +248,11 @@ def __new__(
         if rng is None:
             rng = model.next_rng()
 
-        if dims is not None and "shape" in kwargs:
-            raise ValueError(
-                f"Passing both `dims` ({dims}) and `shape` ({kwargs['shape']}) is not supported!"
-            )
-        if dims is not None and "size" in kwargs:
-            raise ValueError(
-                f"Passing both `dims` ({dims}) and `size` ({kwargs['size']}) is not supported!"
-            )
-        dims = convert_dims(dims)
-
-        # Create the RV without dims information, because that's not something tracked at the Aesara level.
-        # If necessary we'll later replicate to a different size implied by already known dims.
-        rv_out = cls.dist(*args, rng=rng, **kwargs)
-        ndim_actual = rv_out.ndim
-        resize_shape = None
-
-        # `dims` are only available with this API, because `.dist()` can be used
-        # without a modelcontext and dims are not tracked at the Aesara level.
-        if dims is not None:
-            ndim_resize, resize_shape, dims = resize_from_dims(dims, ndim_actual, model)
-        elif observed is not None:
-            ndim_resize, resize_shape, observed = resize_from_observed(observed, ndim_actual)
+        # Create the RV and process dims and observed to determine
+        # a shape by which the created RV may need to be resized.
+        rv_out, dims, observed, resize_shape = _make_rv_and_resize_shape(
+            cls=cls, dims=dims, model=model, observed=observed, args=args, rng=rng, **kwargs
+        )
 
         if resize_shape:
             # A batch size was specified through `dims`, or implied by `observed`.
@@ -456,35 +474,18 @@ def __new__(
         if not isinstance(name, string_types):
             raise TypeError(f"Name needs to be a string but got: {name}")
 
-        if dims is not None and "shape" in kwargs:
-            raise ValueError(
-                f"Passing both `dims` ({dims}) and `shape` ({kwargs['shape']}) is not supported!"
-            )
-        if dims is not None and "size" in kwargs:
-            raise ValueError(
-                f"Passing both `dims` ({dims}) and `size` ({kwargs['size']}) is not supported!"
-            )
-        dims = convert_dims(dims)
-
         if rngs is None:
             # Create a temporary rv to obtain number of rngs needed
             temp_graph = cls.dist(*args, rngs=None, **kwargs)
             rngs = [model.next_rng() for _ in cls.graph_rvs(temp_graph)]
         elif not isinstance(rngs, (list, tuple)):
             rngs = [rngs]
 
-        # Create the RV without dims information, because that's not something tracked at the Aesara level.
-        # If necessary we'll later replicate to a different size implied by already known dims.
-        rv_out = cls.dist(*args, rngs=rngs, **kwargs)
-        ndim_actual = rv_out.ndim
-        resize_shape = None
-
-        # # `dims` are only available with this API, because `.dist()` can be used
-        # # without a modelcontext and dims are not tracked at the Aesara level.
-        if dims is not None:
-            ndim_resize, resize_shape, dims = resize_from_dims(dims, ndim_actual, model)
-        elif observed is not None:
-            ndim_resize, resize_shape, observed = resize_from_observed(observed, ndim_actual)
+        # Create the RV and process dims and observed to determine
+        # a shape by which the created RV may need to be resized.
+        rv_out, dims, observed, resize_shape = _make_rv_and_resize_shape(
+            cls=cls, dims=dims, model=model, observed=observed, args=args, rngs=rngs, **kwargs
+        )
 
         if resize_shape:
             # A batch size was specified through `dims`, or implied by `observed`.

pymc/distributions/shape_utils.py

@@ -427,7 +427,7 @@ def broadcast_dist_samples_to(to_shape, samples, size=None):
 StrongSize = Union[TensorVariable, Tuple[Union[int, TensorVariable], ...]]
 
 
-def convert_dims(dims: Dims) -> Optional[WeakDims]:
+def convert_dims(dims: Optional[Dims]) -> Optional[WeakDims]:
     """Process a user-provided dims variable into None or a valid dims tuple."""
     if dims is None:
         return None
@@ -487,9 +487,7 @@ def convert_size(size: Size) -> Optional[StrongSize]:
     return size
 
 
-def resize_from_dims(
-    dims: WeakDims, ndim_implied: int, model
-) -> Tuple[int, StrongSize, StrongDims]:
+def resize_from_dims(dims: WeakDims, ndim_implied: int, model) -> Tuple[StrongSize, StrongDims]:
     """Determines a potential resize shape from a `dims` tuple.
 
     Parameters
@@ -503,10 +501,10 @@ def resize_from_dims(
 
     Returns
     -------
-    ndim_resize : int
-        Number of dimensions that should be added through resizing.
     resize_shape : array-like
-        The shape of the new dimensions.
+        Shape of new dimensions that should be prepended.
+    dims : tuple of (str or None)
+        Names or None for all dimensions after resizing.
     """
     if Ellipsis in dims:
         # Auto-complete the dims tuple to the full length.
@@ -525,12 +523,12 @@ def resize_from_dims(
 
     # The numeric/symbolic resize tuple can be created using model.RV_dim_lengths
     resize_shape = tuple(model.dim_lengths[dname] for dname in dims[:ndim_resize])
-    return ndim_resize, resize_shape, dims
+    return resize_shape, dims
 
 
 def resize_from_observed(
     observed, ndim_implied: int
-) -> Tuple[int, StrongSize, Union[np.ndarray, Variable]]:
+) -> Tuple[StrongSize, Union[np.ndarray, Variable]]:
     """Determines a potential resize shape from observations.
 
     Parameters
@@ -542,18 +540,16 @@ def resize_from_observed(
 
     Returns
     -------
-    ndim_resize : int
-        Number of dimensions that should be added through resizing.
     resize_shape : array-like
-        The shape of the new dimensions.
+        Shape of new dimensions that should be prepended.
     observed : scalar, array-like
         Observations as numpy array or `Variable`.
     """
     if not hasattr(observed, "shape"):
         observed = pandas_to_array(observed)
     ndim_resize = observed.ndim - ndim_implied
     resize_shape = tuple(observed.shape[d] for d in range(ndim_resize))
-    return ndim_resize, resize_shape, observed
+    return resize_shape, observed
 
 
 def find_size(shape=None, size=None, ndim_supp=None):

pymc/tests/test_shape_handling.py

@@ -293,6 +293,47 @@ def test_param_and_batch_shape_combos(
                     else:
                         raise NotImplementedError("Invalid test case parametrization.")
 
+    @pytest.mark.parametrize("ellipsis_in", ["none", "shape", "dims", "both"])
+    def test_simultaneous_shape_and_dims(self, ellipsis_in):
+        with pm.Model() as pmodel:
+            x = pm.ConstantData("x", [1, 2, 3], dims="ddata")
+
+            if ellipsis_in == "none":
+                # The shape and dims tuples correspond to each other.
+                # Note: No checks are performed that implied shape (x), shape and dims actually match.
+                y = pm.Normal("y", mu=x, shape=(2, 3), dims=("dshape", "ddata"))
+                assert pmodel.RV_dims["y"] == ("dshape", "ddata")
+            elif ellipsis_in == "shape":
+                y = pm.Normal("y", mu=x, shape=(2, ...), dims=("dshape", "ddata"))
+                assert pmodel.RV_dims["y"] == ("dshape", "ddata")
+            elif ellipsis_in == "dims":
+                y = pm.Normal("y", mu=x, shape=(2, 3), dims=("dshape", ...))
+                assert pmodel.RV_dims["y"] == ("dshape", None)
+            elif ellipsis_in == "both":
+                y = pm.Normal("y", mu=x, shape=(2, ...), dims=("dshape", ...))
+                assert pmodel.RV_dims["y"] == ("dshape", None)
+
+            assert "dshape" in pmodel.dim_lengths
+            assert y.eval().shape == (2, 3)
+
+    @pytest.mark.parametrize("with_dims_ellipsis", [False, True])
+    def test_simultaneous_size_and_dims(self, with_dims_ellipsis):
+        with pm.Model() as pmodel:
+            x = pm.ConstantData("x", [1, 2, 3], dims="ddata")
+            assert "ddata" in pmodel.dim_lengths
+
+            # Size does not include support dims, so this test must use a dist with support dims.
+            kwargs = dict(name="y", size=2, mu=at.ones((3, 4)), cov=at.eye(4))
+            if with_dims_ellipsis:
+                y = pm.MvNormal(**kwargs, dims=("dsize", ...))
+                assert pmodel.RV_dims["y"] == ("dsize", None, None)
+            else:
+                y = pm.MvNormal(**kwargs, dims=("dsize", "ddata", "dsupport"))
+                assert pmodel.RV_dims["y"] == ("dsize", "ddata", "dsupport")
+
+            assert "dsize" in pmodel.dim_lengths
+            assert y.eval().shape == (2, 3, 4)
+
     def test_define_dims_on_the_fly(self):
         with pm.Model() as pmodel:
             agedata = aesara.shared(np.array([10, 20, 30]))
@@ -312,17 +353,6 @@ def test_define_dims_on_the_fly(self):
             # The change should propagate all the way through
             assert effect.eval().shape == (4,)
 
-    @pytest.mark.xfail(reason="Simultaneous use of size and dims is not implemented")
-    def test_data_defined_size_dimension_can_register_dimname(self):
-        with pm.Model() as pmodel:
-            x = pm.ConstantData("x", [[1, 2, 3, 4]], dims=("first", "second"))
-            assert "first" in pmodel.dim_lengths
-            assert "second" in pmodel.dim_lengths
-            # two dimensions are implied; a "third" dimension is created
-            y = pm.Normal("y", mu=x, size=2, dims=("third", "first", "second"))
-            assert "third" in pmodel.dim_lengths
-            assert y.eval().shape() == (2, 1, 4)
-
     def test_can_resize_data_defined_size(self):
         with pm.Model() as pmodel:
             x = pm.MutableData("x", [[1, 2, 3, 4]], dims=("first", "second"))
@@ -447,9 +477,3 @@ def test_lazy_flavors(self):
     def test_invalid_flavors(self):
         with pytest.raises(ValueError, match="Passing both"):
             pm.Normal.dist(0, 1, shape=(3,), size=(3,))
-
-        with pm.Model():
-            with pytest.raises(ValueError, match="Passing both"):
-                pm.Normal("n", shape=(2,), dims=("town",))
-            with pytest.raises(ValueError, match="Passing both"):
-                pm.Normal("n", dims=("town",), size=(2,))