BUG: core/umath: do not create views unnecessarily in ndarray.__array_prepare__ (fixes #1548)

2 files changed, 14 insertions, 0 deletions

diff --git a/numpy/core/src/multiarray/methods.c b/numpy/core/src/multiarray/methods.c
index 0d7180a01..783554965 100644
--- a/numpy/core/src/multiarray/methods.c
+++ b/numpy/core/src/multiarray/methods.c
@@ -843,6 +843,12 @@ array_preparearray(PyArrayObject *self, PyObject *args)
         return NULL;
     }
 
+    if (Py_TYPE(self) == Py_TYPE(arr)) {
+        /* No need to create a new view */
+        Py_INCREF(arr);
+        return arr;
+    }
+
     Py_INCREF(PyArray_DESCR(arr));
     ret = PyArray_NewFromDescr(Py_TYPE(self),
                                PyArray_DESCR(arr),
diff --git a/numpy/core/tests/test_regression.py b/numpy/core/tests/test_regression.py
index bc88eed3c..1257a54c2 100644
--- a/numpy/core/tests/test_regression.py
+++ b/numpy/core/tests/test_regression.py
@@ -1351,5 +1351,13 @@ class TestRegression(TestCase):
         x[(0,)] = 2 # shouldn't raise an exception
         assert_equal(x[0], 2)
 
+    def test_ufunc_no_unnecessary_views(self):
+        # ticket #1548
+        class Subclass(np.ndarray):
+            pass
+        x = np.array([1,2,3]).view(Subclass)
+        y = np.add(x, x, x)
+        assert_equal(id(x), id(y))
+
 if __name__ == "__main__":
     run_module_suite()