Introduce signature instead of ndim_supp and ndims_params

pytensor/tensor/random/op.py

+import warnings
 from collections.abc import Sequence
 from copy import copy
 from typing import cast
@@ -28,6 +29,7 @@ from pytensor.tensor.random.utils import (
 from pytensor.tensor.shape import shape_tuple
 from pytensor.tensor.type import TensorType, all_dtypes
 from pytensor.tensor.type_other import NoneConst
+from pytensor.tensor.utils import _parse_gufunc_signature, safe_signature
 from pytensor.tensor.variable import TensorVariable
 
 
@@ -42,7 +44,7 @@ class RandomVariable(Op):
 
     _output_type_depends_on_input_value = True
 
-    __props__ = ("name", "ndim_supp", "ndims_params", "dtype", "inplace")
+    __props__ = ("name", "signature", "dtype", "inplace")
     default_output = 1
 
     def __init__(
@@ -50,8 +52,9 @@ class RandomVariable(Op):
         name=None,
         ndim_supp=None,
         ndims_params=None,
-        dtype=None,
+        dtype: str | None = None,
         inplace=None,
+        signature: str | None = None,
     ):
         """Create a random variable `Op`.
 
@@ -59,44 +62,63 @@ class RandomVariable(Op):
         ----------
         name: str
             The `Op`'s display name.
-        ndim_supp: int
-            Total number of dimensions for a single draw of the random variable
-            (e.g. a multivariate normal draw is 1D, so ``ndim_supp = 1``).
-        ndims_params: list of int
-            Number of dimensions for each distribution parameter when the
-            parameters only specify a single drawn of the random variable
-            (e.g. a multivariate normal's mean is 1D and covariance is 2D, so
-            ``ndims_params = [1, 2]``).
+        signature: str
+            Numpy-like vectorized signature of the random variable.
         dtype: str (optional)
             The dtype of the sampled output.  If the value ``"floatX"`` is
             given, then ``dtype`` is set to ``pytensor.config.floatX``.  If
             ``None`` (the default), the `dtype` keyword must be set when
             `RandomVariable.make_node` is called.
         inplace: boolean (optional)
-            Determine whether or not the underlying rng state is updated
-            in-place or not (i.e. copied).
+            Determine whether the underlying rng state is mutated or copied.
 
         """
         super().__init__()
 
         self.name = name or getattr(self, "name")
-        self.ndim_supp = (
-            ndim_supp if ndim_supp is not None else getattr(self, "ndim_supp")
+
+        ndim_supp = (
+            ndim_supp if ndim_supp is not None else getattr(self, "ndim_supp", None)
         )
-        self.ndims_params = (
-            ndims_params if ndims_params is not None else getattr(self, "ndims_params")
+        if ndim_supp is not None:
+            warnings.warn(
+                "ndim_supp is deprecated. Provide signature instead.", FutureWarning
+            )
+            self.ndim_supp = ndim_supp
+        ndims_params = (
+            ndims_params
+            if ndims_params is not None
+            else getattr(self, "ndims_params", None)
         )
+        if ndims_params is not None:
+            warnings.warn(
+                "ndims_params is deprecated. Provide signature instead.", FutureWarning
+            )
+            if not isinstance(ndims_params, Sequence):
+                raise TypeError("Parameter ndims_params must be sequence type.")
+            self.ndims_params = tuple(ndims_params)
+
+        self.signature = signature or getattr(self, "signature", None)
+        if self.signature is not None:
+            # Assume a single output. Several methods need to be updated to handle multiple outputs.
+            self.inputs_sig, [self.output_sig] = _parse_gufunc_signature(self.signature)
+            self.ndims_params = [len(input_sig) for input_sig in self.inputs_sig]
+            self.ndim_supp = len(self.output_sig)
+        else:
+            if (
+                getattr(self, "ndim_supp", None) is None
+                or getattr(self, "ndims_params", None) is None
+            ):
+                raise ValueError("signature must be provided")
+            else:
+                self.signature = safe_signature(self.ndims_params, [self.ndim_supp])
+
         self.dtype = dtype or getattr(self, "dtype", None)
 
         self.inplace = (
             inplace if inplace is not None else getattr(self, "inplace", False)
         )
 
-        if not isinstance(self.ndims_params, Sequence):
-            raise TypeError("Parameter ndims_params must be sequence type.")
-
-        self.ndims_params = tuple(self.ndims_params)
-
         if self.inplace:
             self.destroy_map = {0: [0]}
 
@@ -120,8 +142,31 @@ class RandomVariable(Op):
         values (not shapes) of some parameters. For instance, a `gaussian_random_walk(steps, size=(2,))`,
         might have `support_shape=(steps,)`.
         """
+        if self.signature is not None:
+            # Signature could indicate fixed numerical shapes
+            # As per https://numpy.org/neps/nep-0020-gufunc-signature-enhancement.html
+            output_sig = self.output_sig
+            core_out_shape = {
+                dim: int(dim) if str.isnumeric(dim) else None for dim in self.output_sig
+            }
+
+            # Try to infer missing support dims from signature of params
+            for param, param_sig, ndim_params in zip(
+                dist_params, self.inputs_sig, self.ndims_params
+            ):
+                if ndim_params == 0:
+                    continue
+                for param_dim, dim in zip(param.shape[-ndim_params:], param_sig):
+                    if dim in core_out_shape and core_out_shape[dim] is None:
+                        core_out_shape[dim] = param_dim
+
+            if all(dim is not None for dim in core_out_shape.values()):
+                # We have all we need
+                return [core_out_shape[dim] for dim in output_sig]
+
         raise NotImplementedError(
-            "`_supp_shape_from_params` must be implemented for multivariate RVs"
+            "`_supp_shape_from_params` must be implemented for multivariate RVs "
+            "when signature is not sufficient to infer the support shape"
         )
 
     def rng_fn(self, rng, *args, **kwargs) -> int | float | np.ndarray:
@@ -129,7 +174,24 @@ class RandomVariable(Op):
         return getattr(rng, self.name)(*args, **kwargs)
 
     def __str__(self):
-        props_str = ", ".join(f"{getattr(self, prop)}" for prop in self.__props__[1:])
+        # Only show signature from core props
+        if signature := self.signature:
+            # inp, out = signature.split("->")
+            # extended_signature = f"[rng],[size],{inp}->[rng],{out}"
+            # core_props = [extended_signature]
+            core_props = [f'"{signature}"']
+        else:
+            # Far back compat
+            core_props = [str(self.ndim_supp), str(self.ndims_params)]
+
+        # Add any extra props that the subclass may have
+        extra_props = [
+            str(getattr(self, prop))
+            for prop in self.__props__
+            if prop not in RandomVariable.__props__
+        ]
+
+        props_str = ", ".join(core_props + extra_props)
         return f"{self.name}_rv{{{props_str}}}"
 
     def _infer_shape(
@@ -298,11 +360,11 @@ class RandomVariable(Op):
             dtype_idx = constant(all_dtypes.index(dtype), dtype="int64")
         else:
             dtype_idx = constant(dtype, dtype="int64")
-            dtype = all_dtypes[dtype_idx.data]
 
-        outtype = TensorType(dtype=dtype, shape=static_shape)
-        out_var = outtype()
+        dtype = all_dtypes[dtype_idx.data]
+
         inputs = (rng, size, dtype_idx, *dist_params)
+        out_var = TensorType(dtype=dtype, shape=static_shape)()
         outputs = (rng.type(), out_var)
 
         return Apply(self, inputs, outputs)
@@ -395,9 +457,8 @@ def vectorize_random_variable(
     # We extend it to accommodate the new input batch dimensions.
     # Otherwise, we assume the new size already has the right values
 
-    # Need to make parameters implicit broadcasting explicit
-    original_dist_params = node.inputs[3:]
-    old_size = node.inputs[1]
+    original_dist_params = op.dist_params(node)
+    old_size = op.size_param(node)
     len_old_size = get_vector_length(old_size)
 
     original_expanded_dist_params = explicit_expand_dims(

pytensor/tensor/random/rewriting/jax.py

+import re
+
 from pytensor.compile import optdb
 from pytensor.graph.rewriting.basic import in2out, node_rewriter
 from pytensor.graph.rewriting.db import SequenceDB
@@ -164,9 +166,9 @@ def materialize_implicit_arange_choice_without_replacement(fgraph, node):
 
     a_vector_param = arange(a_scalar_param)
     new_props_dict = op._props_dict().copy()
-    new_ndims_params = list(op.ndims_params)
-    new_ndims_params[0] += 1
-    new_props_dict["ndims_params"] = new_ndims_params
+    # Signature changes from something like "(),(a),(2)->(s0, s1)" to "(a),(a),(2)->(s0, s1)"
+    # I.e., we substitute the first `()` by `(a)`
+    new_props_dict["signature"] = re.sub(r"\(\)", "(a)", op.signature, 1)
     new_op = type(op)(**new_props_dict)
     return new_op.make_node(rng, size, dtype, a_vector_param, *other_params).outputs
 

pytensor/tensor/random/utils.py

@@ -123,7 +123,7 @@ def broadcast_params(params, ndims_params):
 
 def explicit_expand_dims(
     params: Sequence[TensorVariable],
-    ndim_params: tuple[int],
+    ndim_params: Sequence[int],
     size_length: int = 0,
 ) -> list[TensorVariable]:
     """Introduce explicit expand_dims in RV parameters that are implicitly broadcasted together and/or by size."""
@@ -137,7 +137,7 @@ def explicit_expand_dims(
         # See: https://github.com/pymc-devs/pytensor/issues/568
         max_batch_dims = size_length
     else:
-        max_batch_dims = max(batch_dims)
+        max_batch_dims = max(batch_dims, default=0)
 
     new_params = []
     for new_param, batch_dim in zip(params, batch_dims):
@@ -354,6 +354,11 @@ def supp_shape_from_ref_param_shape(
     out: tuple
         Representing the support shape for a `RandomVariable` with the given `dist_params`.
 
+    Notes
+    _____
+    This helper is no longer necessary when using signatures in `RandomVariable` subclasses.
+
+
     """
     if ndim_supp <= 0:
         raise ValueError("ndim_supp must be greater than 0")

pytensor/tensor/utils.py

@@ -169,7 +169,8 @@ _DIMENSION_NAME = r"\w+"
 _CORE_DIMENSION_LIST = f"(?:{_DIMENSION_NAME}(?:,{_DIMENSION_NAME})*)?"
 _ARGUMENT = rf"\({_CORE_DIMENSION_LIST}\)"
 _ARGUMENT_LIST = f"{_ARGUMENT}(?:,{_ARGUMENT})*"
-_SIGNATURE = f"^{_ARGUMENT_LIST}->{_ARGUMENT_LIST}$"
+# Allow no inputs
+_SIGNATURE = f"^(?:{_ARGUMENT_LIST})?->{_ARGUMENT_LIST}$"
 
 
 def _parse_gufunc_signature(
@@ -200,6 +201,8 @@ def _parse_gufunc_signature(
             tuple(re.findall(_DIMENSION_NAME, arg))
             for arg in re.findall(_ARGUMENT, arg_list)
         ]
+        if arg_list  # ignore no inputs
+        else []
         for arg_list in signature.split("->")
     )
 

tests/link/jax/test_random.py

@@ -771,8 +771,7 @@ def test_random_unimplemented():
 
     class NonExistentRV(RandomVariable):
         name = "non-existent"
-        ndim_supp = 0
-        ndims_params = []
+        signature = "->()"
         dtype = "floatX"
 
         def __call__(self, size=None, **kwargs):
@@ -798,8 +797,7 @@ def test_random_custom_implementation():
 
     class CustomRV(RandomVariable):
         name = "non-existent"
-        ndim_supp = 0
-        ndims_params = []
+        signature = "->()"
         dtype = "floatX"
 
         def __call__(self, size=None, **kwargs):

tests/tensor/random/rewriting/test_basic.py

@@ -74,52 +74,28 @@ def apply_local_rewrite_to_rv(
     return new_out, f_inputs, dist_st, f_rewritten
 
 
-def test_inplace_rewrites():
-    out = normal(0, 1)
-    out.owner.inputs[0].default_update = out.owner.outputs[0]
+class TestRVExpraProps(RandomVariable):
+    name = "test"
+    signature = "()->()"
+    __props__ = ("name", "signature", "dtype", "inplace", "extra")
+    dtype = "floatX"
+    _print_name = ("TestExtraProps", "\\operatorname{TestExtra_props}")
 
-    assert out.owner.op.inplace is False
+    def __init__(self, extra, *args, **kwargs):
+        self.extra = extra
+        super().__init__(*args, **kwargs)
 
-    f = function(
-        [],
-        out,
-        mode="FAST_RUN",
-    )
-
-    (new_out, new_rng) = f.maker.fgraph.outputs
-    assert new_out.type == out.type
-    assert isinstance(new_out.owner.op, type(out.owner.op))
-    assert new_out.owner.op.inplace is True
-    assert all(
-        np.array_equal(a.data, b.data)
-        for a, b in zip(new_out.owner.inputs[2:], out.owner.inputs[2:])
-    )
-    assert np.array_equal(new_out.owner.inputs[1].data, [])
-
-
-def test_inplace_rewrites_extra_props():
-    class Test(RandomVariable):
-        name = "test"
-        ndim_supp = 0
-        ndims_params = [0]
-        __props__ = ("name", "ndim_supp", "ndims_params", "dtype", "inplace", "extra")
-        dtype = "floatX"
-        _print_name = ("Test", "\\operatorname{Test}")
-
-        def __init__(self, extra, *args, **kwargs):
-            self.extra = extra
-            super().__init__(*args, **kwargs)
-
-        def make_node(self, rng, size, dtype, sigma):
-            return super().make_node(rng, size, dtype, sigma)
-
-        def rng_fn(self, rng, sigma, size):
-            return rng.normal(scale=sigma, size=size)
+    def rng_fn(self, rng, dtype, sigma, size):
+        return rng.normal(scale=sigma, size=size)
 
-    out = Test(extra="some value")(1)
-    out.owner.inputs[0].default_update = out.owner.outputs[0]
 
-    assert out.owner.op.inplace is False
+@pytest.mark.parametrize("rv_op", [normal, TestRVExpraProps(extra="some value")])
+def test_inplace_rewrites(rv_op):
+    out = rv_op(np.e)
+    node = out.owner
+    op = node.op
+    node.inputs[0].default_update = node.outputs[0]
+    assert op.inplace is False
 
     f = function(
         [],
@@ -129,9 +105,10 @@ def test_inplace_rewrites_extra_props():
 
     (new_out, new_rng) = f.maker.fgraph.outputs
     assert new_out.type == out.type
-    assert isinstance(new_out.owner.op, type(out.owner.op))
-    assert new_out.owner.op.inplace is True
-    assert new_out.owner.op.extra == out.owner.op.extra
+    new_node = new_out.owner
+    new_op = new_node.op
+    assert isinstance(new_op, type(op))
+    assert new_op._props_dict() == (op._props_dict() | {"inplace": True})
     assert all(
         np.array_equal(a.data, b.data)
         for a, b in zip(new_out.owner.inputs[2:], out.owner.inputs[2:])

tests/tensor/random/test_basic.py

@@ -1463,11 +1463,8 @@ def batched_unweighted_choice_without_replacement_tester(
     rng = shared(rng_ctor())
 
     # Batched a implicit size
-    a_core_ndim = 2
-    core_shape_len = 1
     rv_op = ChoiceWithoutReplacement(
-        ndim_supp=max(a_core_ndim - 1, 0) + core_shape_len,
-        ndims_params=[a_core_ndim, core_shape_len],
+        signature="(a0,a1),(1)->(s0,a1)",
         dtype="int64",
     )
 
@@ -1483,11 +1480,8 @@ def batched_unweighted_choice_without_replacement_tester(
         assert np.all((draw >= i * 10) & (draw < (i + 1) * 10))
 
     # Explicit size broadcasts beyond a
-    a_core_ndim = 2
-    core_shape_len = 2
     rv_op = ChoiceWithoutReplacement(
-        ndim_supp=max(a_core_ndim - 1, 0) + core_shape_len,
-        ndims_params=[a_core_ndim, len(core_shape)],
+        signature="(a0,a1),(2)->(s0,s1,a1)",
         dtype="int64",
     )
 
@@ -1515,12 +1509,8 @@ def batched_weighted_choice_without_replacement_tester(
     """
     rng = shared(rng_ctor())
 
-    # 3 ndims params indicates p is passed
-    a_core_ndim = 2
-    core_shape_len = 1
     rv_op = ChoiceWithoutReplacement(
-        ndim_supp=max(a_core_ndim - 1, 0) + core_shape_len,
-        ndims_params=[a_core_ndim, 1, 1],
+        signature="(a0,a1),(a0),(1)->(s0,a1)",
         dtype="int64",
     )
 
@@ -1540,11 +1530,8 @@ def batched_weighted_choice_without_replacement_tester(
 
     # p and a are batched
     # Test implicit arange
-    a_core_ndim = 0
-    core_shape_len = 2
     rv_op = ChoiceWithoutReplacement(
-        ndim_supp=max(a_core_ndim - 1, 0) + core_shape_len,
-        ndims_params=[a_core_ndim, 1, 1],
+        signature="(),(a),(2)->(s0,s1)",
         dtype="int64",
     )
     a = 6
@@ -1566,11 +1553,8 @@ def batched_weighted_choice_without_replacement_tester(
         assert set(draw) == set(range(i, 6, 2))
 
     # Size broadcasts beyond a
-    a_core_ndim = 2
-    core_shape_len = 1
     rv_op = ChoiceWithoutReplacement(
-        ndim_supp=max(a_core_ndim - 1, 0) + core_shape_len,
-        ndims_params=[a_core_ndim, 1, 1],
+        signature="(a0,a1),(a0),(1)->(s0,a1)",
         dtype="int64",
     )
     a = np.arange(4 * 5 * 2).reshape((4, 5, 2))

tests/tensor/random/test_op.py

@@ -23,14 +23,13 @@ def test_RandomVariable_basics(strict_test_value_flags):
     str_res = str(
         RandomVariable(
             "normal",
-            0,
-            [0, 0],
-            "float32",
-            inplace=True,
+            signature="(),()->()",
+            dtype="float32",
+            inplace=False,
         )
     )
 
-    assert str_res == "normal_rv{0, (0, 0), float32, True}"
+    assert str_res == 'normal_rv{"(),()->()"}'
 
     # `ndims_params` should be a `Sequence` type
     with pytest.raises(TypeError, match="^Parameter ndims_params*"):
@@ -64,9 +63,7 @@ def test_RandomVariable_basics(strict_test_value_flags):
     # Confirm that `inplace` works
     rv = RandomVariable(
         "normal",
-        0,
-        [0, 0],
-        "normal",
+        signature="(),()->()",
         inplace=True,
     )
 
@@ -74,7 +71,7 @@ def test_RandomVariable_basics(strict_test_value_flags):
     assert rv.destroy_map == {0: [0]}
 
     # A no-params `RandomVariable`
-    rv = RandomVariable(name="test_rv", ndim_supp=0, ndims_params=())
+    rv = RandomVariable(name="test_rv", signature="->()")
 
     with pytest.raises(TypeError):
         rv.make_node(rng=1)