Bug/1017 prod / sum with empty arrays (#1018)

* Check for split in `__reduce_op`

* Check whether x is distributed

Co-authored-by: mtar <m.tarnawa@fz-juelich.de>

Co-authored-by: mtar <m.tarnawa@fz-juelich.de>
Co-authored-by: Claudia Comito <39374113+ClaudiaComito@users.noreply.github.com>

heat/core/_operations.py

@@ -422,7 +422,7 @@ def __reduce_op(
     balanced = x.balanced
 
     # if local tensor is empty, replace it with the identity element
-    if 0 in x.lshape and (axis is None or (x.split in axis)):
+    if x.is_distributed() and 0 in x.lshape and (axis is None or split in axis):
         if neutral is None:
             neutral = float("nan")
         neutral_shape = x.gshape[:split] + (1,) + x.gshape[split + 1 :]

heat/core/tests/test_arithmetics.py

@@ -646,6 +646,10 @@ def test_prod(self):
         self.assertEqual(shape_split_axis_tuple_prod.split, None)
         self.assertTrue((shape_split_axis_tuple_prod == expected_result).all())
 
+        # empty array
+        empty = ht.array([])
+        self.assertEqual(ht.prod(empty), ht.array([1.0]))
+
         # exceptions
         with self.assertRaises(ValueError):
             ht.ones(array_len).prod(axis=1)
@@ -792,6 +796,10 @@ def test_sum(self):
         self.assertEqual(shape_split_axis_tuple_sum.split, None)
         self.assertTrue((shape_split_axis_tuple_sum == expected_result).all())
 
+        # empty array
+        empty = ht.array([])
+        self.assertEqual(ht.sum(empty), ht.array([0.0]))
+
         # exceptions
         with self.assertRaises(ValueError):
             ht.ones(array_len).sum(axis=1)