Work-around numba pow failure was not robust enough

pytensor/link/numba/dispatch/scalar.py

@@ -170,18 +170,17 @@ def {binary_op_name}({input_signature}):
 @register_funcify_and_cache_key(Pow)
 def numba_funcify_Pow(op, node, **kwargs):
     pow_dtype = node.inputs[1].type.dtype
-    if pow_dtype.startswith("int"):
-        # Numba power fails when exponents are non 64-bit discrete integers and fasthmath=True
-        # https://github.com/numba/numba/issues/9554
-
-        def pow(x, y):
-            return x ** np.asarray(y, dtype=np.int64).item()
-    else:
 
     def pow(x, y):
         return x**y
 
-    return numba_basic.numba_njit(pow), scalar_op_cache_key(op)
+    # Numba power fails when exponents are discrete integers and fasthmath=True
+    # https://github.com/numba/numba/issues/9554
+    fastmath = False if np.dtype(pow_dtype).kind in "ibu" else None
+
+    return numba_basic.numba_njit(pow, fastmath=fastmath), scalar_op_cache_key(
+        op, cache_version=1
+    )
 
 
 @register_funcify_and_cache_key(Add)

tests/link/numba/test_scalar.py

@@ -183,13 +183,23 @@ def test_Softplus(dtype):
         )
 
 
-def test_discrete_power():
+@pytest.mark.parametrize(
+    "test_base",
+    [np.bool(True), np.int16(3), np.uint16(3), np.float32(0.5), np.float64(0.5)],
+)
+@pytest.mark.parametrize(
+    "test_exponent",
+    [np.bool(True), np.int16(2), np.uint16(2), np.float32(2.0), np.float64(2.0)],
+)
+def test_power_fastmath_bug(test_base, test_exponent):
     # Test we don't fail to compile power with discrete exponents due to https://github.com/numba/numba/issues/9554
-    x = pt.scalar("x", dtype="float64")
-    exponent = pt.scalar("exponent", dtype="int8")
-    out = pt.power(x, exponent)
+    base = pt.scalar("base", dtype=test_base.dtype)
+    exponent = pt.scalar("exponent", dtype=test_exponent.dtype)
+    out = pt.power(base, exponent)
     compare_numba_and_py(
-        [x, exponent], [out], [np.array(0.5), np.array(2, dtype="int8")]
+        [base, exponent],
+        [out],
+        [test_base, test_exponent],
     )