Respect check_finite in LU decomposition rewrites

pytensor/tensor/_linalg/solve/rewriting.py

@@ -14,16 +14,22 @@ from pytensor.tensor.slinalg import Solve, lu_factor, lu_solve
 from pytensor.tensor.variable import TensorVariable
 
 
-def decompose_A(A, assume_a):
+def decompose_A(A, assume_a, check_finite):
     if assume_a == "gen":
-        return lu_factor(A, check_finite=False)
+        return lu_factor(A, check_finite=check_finite)
     else:
         raise NotImplementedError
 
 
-def solve_lu_decomposed_system(A_decomp, b, b_ndim, assume_a, transposed=False):
-    if assume_a == "gen":
-        return lu_solve(A_decomp, b, b_ndim=b_ndim, trans=transposed)
+def solve_lu_decomposed_system(A_decomp, b, transposed=False, *, core_solve_op: Solve):
+    if core_solve_op.assume_a == "gen":
+        return lu_solve(
+            A_decomp,
+            b,
+            trans=transposed,
+            b_ndim=core_solve_op.b_ndim,
+            check_finite=core_solve_op.check_finite,
+        )
     else:
         raise NotImplementedError
 
@@ -102,14 +108,19 @@ def _split_lu_solve_steps(
         ):
             return None
 
-    A_decomp = decompose_A(A, assume_a=assume_a)
+    # If any Op had check_finite=True, we also do it for the LU decomposition
+    check_finite_decomp = False
+    for client, _ in A_solve_clients_and_transpose:
+        if client.op.core_op.check_finite:
+            check_finite_decomp = True
+            break
+    A_decomp = decompose_A(A, assume_a=assume_a, check_finite=check_finite_decomp)
 
     replacements = {}
     for client, transposed in A_solve_clients_and_transpose:
         _, b = client.inputs
-        b_ndim = client.op.core_op.b_ndim
         new_x = solve_lu_decomposed_system(
-            A_decomp, b, b_ndim=b_ndim, assume_a=assume_a, transposed=transposed
+            A_decomp, b, transposed=transposed, core_solve_op=client.op.core_op
         )
         [old_x] = client.outputs
         new_x = atleast_Nd(new_x, n=old_x.type.ndim).astype(old_x.type.dtype)

pytensor/tensor/type.py

@@ -793,7 +793,7 @@ def tensor(
         try:
             # Help catching errors with the new tensor API
             # Many single letter strings are valid sctypes
-            if str(name) == "floatX" or (len(str(name)) > 1 and np.dtype(name).type):
+            if str(name) == "floatX" or (len(str(name)) > 2 and np.dtype(name).type):
                 raise ValueError(
                     f"The first and only positional argument of tensor is now `name`. Got {name}.\n"
                     "This name looks like a dtype, which you should pass as a keyword argument only."

tests/tensor/linalg/test_rewriting.py

@@ -161,3 +161,36 @@ def test_lu_decomposition_reused_scan(transposed):
     resx1 = fn_opt(A_test, x0_test)
     rtol = 1e-7 if config.floatX == "float64" else 1e-6
     np.testing.assert_allclose(resx0, resx1, rtol=rtol)
+
+
+def test_lu_decomposition_reused_preserves_check_finite():
+    # Check that the LU decomposition rewrite preserves the check_finite flag
+    rewrite_name = reuse_lu_decomposition_multiple_solves.__name__
+
+    A = tensor("A", shape=(2, 2))
+    b1 = tensor("b1", shape=(2,))
+    b2 = tensor("b2", shape=(2,))
+
+    x1 = solve(A, b1, assume_a="gen", check_finite=True)
+    x2 = solve(A, b2, assume_a="gen", check_finite=False)
+    fn_opt = function(
+        [A, b1, b2], [x1, x2], mode=get_default_mode().including(rewrite_name)
+    )
+    opt_nodes = fn_opt.maker.fgraph.apply_nodes
+    assert count_vanilla_solve_nodes(opt_nodes) == 0
+    assert count_lu_decom_nodes(opt_nodes) == 1
+    assert count_lu_solve_nodes(opt_nodes) == 2
+
+    # We should get an error if A or b1 is non finite
+    A_valid = np.array([[1, 0], [0, 1]], dtype=A.type.dtype)
+    b1_valid = np.array([1, 1], dtype=b1.type.dtype)
+    b2_valid = np.array([1, 1], dtype=b2.type.dtype)
+
+    assert fn_opt(A_valid, b1_valid, b2_valid)  # Fine
+    assert fn_opt(
+        A_valid, b1_valid, b2_valid * np.nan
+    )  # Should not raise (also fine on most LAPACK implementations?)
+    with pytest.raises(ValueError, match="array must not contain infs or NaNs"):
+        assert fn_opt(A_valid, b1_valid * np.nan, b2_valid)
+    with pytest.raises(ValueError, match="array must not contain infs or NaNs"):
+        assert fn_opt(A_valid * np.nan, b1_valid, b2_valid)