Fix shape errors in scalar_solve_to_division rewrite

pytensor/tensor/rewriting/linalg.py

@@ -1046,11 +1046,15 @@ def scalar_solve_to_division(fgraph, node):
     if not all(a.broadcastable[-2:]):
         return None
 
+    if core_op.b_ndim == 1:
+        # Convert b to a column matrix
+        b = b[..., None]
+
     # Special handling for different types of solve
     match core_op:
         case SolveTriangular():
             # Corner case: if user asked for a triangular solve with a unit diagonal, a is taken to be 1
-            new_out = b / a if not core_op.unit_diagonal else b
+            new_out = b / a if not core_op.unit_diagonal else pt.second(a, b)
         case CholeskySolve():
             new_out = b / a**2
         case Solve():
@@ -1061,6 +1065,7 @@ def scalar_solve_to_division(fgraph, node):
             )
 
     if core_op.b_ndim == 1:
+        # Squeeze away the column dimension added earlier
         new_out = new_out.squeeze(-1)
 
     copy_stack_trace(old_out, new_out)

tests/tensor/rewriting/test_linalg.py

@@ -10,6 +10,7 @@
 from pytensor import tensor as pt
 from pytensor.compile import get_default_mode
 from pytensor.configdefaults import config
+from pytensor.graph import ancestors
 from pytensor.graph.rewriting.utils import rewrite_graph
 from pytensor.tensor import swapaxes
 from pytensor.tensor.blockwise import Blockwise
@@ -989,34 +990,73 @@ def test_slogdet_specialization():
 
 
 @pytest.mark.parametrize(
-    "Op, fn",
+    "a_batch_shape", [(), (5,)], ids=lambda x: f"a_batch_shape={x}"
+)
+@pytest.mark.parametrize(
+    "b_batch_shape", [(), (5,)], ids=lambda x: f"b_batch_shape={x}"
+)
+@pytest.mark.parametrize("b_ndim", (1, 2), ids=lambda x: f"b_ndim={x}")
+@pytest.mark.parametrize(
+    "op, fn, extra_kwargs",
     [
-        (Solve, pt.linalg.solve),
-        (SolveTriangular, pt.linalg.solve_triangular),
-        (CholeskySolve, pt.linalg.cho_solve),
+        (Solve, pt.linalg.solve, {}),
+        (SolveTriangular, pt.linalg.solve_triangular, {}),
+        (SolveTriangular, pt.linalg.solve_triangular, {"unit_diagonal": True}),
+        (CholeskySolve, pt.linalg.cho_solve, {}),
     ],
 )
-def test_scalar_solve_to_division_rewrite(Op, fn):
-    rng = np.random.default_rng(sum(map(ord, "scalar_solve_to_division_rewrite")))
+def test_scalar_solve_to_division_rewrite(
+    op, fn, extra_kwargs, b_ndim, a_batch_shape, b_batch_shape
+):
+    def solve_op_in_graph(graph):
+        return any(
+            isinstance(var.owner.op, SolveBase)
+            or (
+                isinstance(var.owner.op, Blockwise)
+                and isinstance(var.owner.op.core_op, SolveBase)
+            )
+            for var in ancestors(graph)
+            if var.owner
+        )
+
+    rng = np.random.default_rng(
+        [
+            sum(map(ord, "scalar_solve_to_division_rewrite")),
+            b_ndim,
+            *a_batch_shape,
+            1,
+            *b_batch_shape,
+        ]
+    )
 
-    a = pt.dmatrix("a", shape=(1, 1))
-    b = pt.dvector("b")
+    a = pt.tensor("a", shape=(*a_batch_shape, 1, 1), dtype="float64")
+    b = pt.tensor("b", shape=(*b_batch_shape, *([None] * b_ndim)), dtype="float64")
 
-    if Op is CholeskySolve:
+    if op is CholeskySolve:
         # cho_solve expects a tuple (c, lower) as the first input
-        c = fn((pt.linalg.cholesky(a), True), b, b_ndim=1)
+        c = fn((pt.linalg.cholesky(a), True), b, b_ndim=b_ndim, **extra_kwargs)
     else:
-        c = fn(a, b, b_ndim=1)
+        c = fn(a, b, b_ndim=b_ndim, **extra_kwargs)
 
+    assert solve_op_in_graph([c])
     f = function([a, b], c, mode="FAST_RUN")
-    nodes = f.maker.fgraph.apply_nodes
+    assert not solve_op_in_graph(f.maker.fgraph.outputs)
+
+    a_val = rng.normal(size=(*a_batch_shape, 1, 1)).astype(pytensor.config.floatX)
+    b_core_shape = (1, 5) if b_ndim == 2 else (1,)
+    b_val = rng.normal(size=(*b_batch_shape, *b_core_shape)).astype(
+        pytensor.config.floatX
+    )
 
-    assert not any(isinstance(node.op, Op) for node in nodes)
+    if op is CholeskySolve:
+        # Avoid sign ambiguity in solve
+        a_val = a_val**2
 
-    a_val = rng.normal(size=(1, 1)).astype(pytensor.config.floatX)
-    b_val = rng.normal(size=(1,)).astype(pytensor.config.floatX)
+    if extra_kwargs.get("unit_diagonal", False):
+        a_val = np.ones_like(a_val)
 
-    c_val = np.linalg.solve(a_val, b_val)
+    signature = "(n,m),(m)->(n)" if b_ndim == 1 else "(n,m),(m,k)->(n,k)"
+    c_val = np.vectorize(np.linalg.solve, signature=signature)(a_val, b_val)
     np.testing.assert_allclose(
         f(a_val, b_val), c_val, rtol=1e-7 if config.floatX == "float64" else 1e-5
     )