Merge pull request #12089 from bashtage/permutation-in-place-bug

BUG: Fix in-place permutation

numpy/random/mtrand/mtrand.pyx

@@ -4907,8 +4907,8 @@ cdef class RandomState:
 
         # shuffle has fast-path for 1-d
         if arr.ndim == 1:
-            # must return a copy
-            if arr is x:
+            # Return a copy if same memory
+            if np.may_share_memory(arr, x):
                 arr = np.array(arr)
             self.shuffle(arr)
             return arr

numpy/random/tests/test_regression.py

@@ -133,3 +133,25 @@ def test_shuffle_of_array_of_objects(self):
         # Force Garbage Collection - should not segfault.
         import gc
         gc.collect()
+
+    def test_permutation_subclass(self):
+        class N(np.ndarray):
+            pass
+
+        np.random.seed(1)
+        orig = np.arange(3).view(N)
+        perm = np.random.permutation(orig)
+        assert_array_equal(perm, np.array([0, 2, 1]))
+        assert_array_equal(orig, np.arange(3).view(N))
+
+        class M(object):
+            a = np.arange(5)
+
+            def __array__(self):
+                return self.a
+
+        np.random.seed(1)
+        m = M()
+        perm = np.random.permutation(m)
+        assert_array_equal(perm, np.array([2, 1, 4, 0, 3]))
+        assert_array_equal(m.__array__(), np.arange(5))