ENH: Explicitly set dtype to int32 due to OS dependant behavior

Author: sweb

pandas/core/reshape/reshape.py

@@ -160,7 +160,7 @@ def _make_selectors(self):
         comp_index = ensure_platform_int(comp_index)
         stride = self.index.levshape[self.level] + self.lift
         self.full_shape = ngroups, stride
-        num_entries = np.prod(self.full_shape)
+        num_entries = np.prod(self.full_shape, dtype=np.int32)
 
         if num_entries < 0:
             raise ValueError('Unstack leads to too many (max int32) entries, '

pandas/tests/reshape/test_reshape.py

@@ -584,6 +584,7 @@ def test_get_dummies_duplicate_columns(self, df):
         tm.assert_frame_equal(result, expected)
 
 
+@pytest.mark.slow
 def test_too_many_items_to_unstack_raises_value_error():
     index = pd.MultiIndex.from_arrays([np.arange(979758),
                                        np.arange(979758)],