Revert "Modifying cartesian product to allow for >2D input arrays (py…

…mc-devs#4482)"

This reverts commit 47b3658.

RELEASE-NOTES.md

@@ -5,7 +5,6 @@
 + ...
 
 ### New Features
-+ `pm.math.cartesian` can now handle inputs that are themselves >1D (see [#4482](https://github.com/pymc-devs/pymc3/pull/4482)).
 + ...
 
 ### Maintenance

pymc3/math.py

@@ -101,17 +101,11 @@ def cartesian(*arrays):
 
     Parameters
     ----------
-    arrays: N-D array-like
-            N-D arrays where earlier arrays loop more slowly than later ones
+    arrays: 1D array-like
+            1D arrays where earlier arrays loop more slowly than later ones
     """
     N = len(arrays)
-    arrays_np = [np.asarray(x) for x in arrays]
-    arrays_2d = [x[:, None] if np.asarray(x).ndim == 1 else x for x in arrays_np]
-    arrays_integer = [np.arange(len(x)) for x in arrays_2d]
-    product_integers = np.stack(np.meshgrid(*arrays_integer, indexing="ij"), -1).reshape(-1, N)
-    return np.concatenate(
-        [array[product_integers[:, i]] for i, array in enumerate(arrays_2d)], axis=-1
-    )
+    return np.stack(np.meshgrid(*arrays, indexing="ij"), -1).reshape(-1, N)
 
 
 def kron_matrix_op(krons, m, op):

pymc3/tests/test_math.py

@@ -71,24 +71,7 @@ def test_cartesian():
         ]
     )
     auto_cart = cartesian(a, b, c)
-    np.testing.assert_array_equal(manual_cartesian, auto_cart)
-
-
-def test_cartesian_2d():
-    np.random.seed(1)
-    a = [[1, 2], [3, 4]]
-    b = [5, 6]
-    c = [0]
-    manual_cartesian = np.array(
-        [
-            [1, 2, 5, 0],
-            [1, 2, 6, 0],
-            [3, 4, 5, 0],
-            [3, 4, 6, 0],
-        ]
-    )
-    auto_cart = cartesian(a, b, c)
-    np.testing.assert_array_equal(manual_cartesian, auto_cart)
+    np.testing.assert_array_almost_equal(manual_cartesian, auto_cart)
 
 
 def test_kron_dot():