Merge pull request #6553 from yashmehrotra/partition-fix

BUG: Fix partition and argpartition error for empty input. Closes #6530

3 files changed, 28 insertions, 2 deletions

diff --git a/numpy/core/src/multiarray/item_selection.c b/numpy/core/src/multiarray/item_selection.c
index ec0717bd6..64fa70b6d 100644
--- a/numpy/core/src/multiarray/item_selection.c
+++ b/numpy/core/src/multiarray/item_selection.c
@@ -809,7 +809,7 @@ _new_sortlike(PyArrayObject *op, int axis, PyArray_SortFunc *sort,
     PyArrayIterObject *it;
     npy_intp size;
 
-    int ret = -1;
+    int ret = 0;
 
     NPY_BEGIN_THREADS_DEF;
 
@@ -829,6 +829,7 @@ _new_sortlike(PyArrayObject *op, int axis, PyArray_SortFunc *sort,
     if (needcopy) {
         buffer = PyDataMem_NEW(N * elsize);
         if (buffer == NULL) {
+            ret = -1;
             goto fail;
         }
     }
@@ -947,7 +948,7 @@ _new_argsortlike(PyArrayObject *op, int axis, PyArray_ArgSortFunc *argsort,
     PyArrayIterObject *it, *rit;
     npy_intp size;
 
-    int ret = -1;
+    int ret = 0;
 
     NPY_BEGIN_THREADS_DEF;
 
@@ -969,6 +970,7 @@ _new_argsortlike(PyArrayObject *op, int axis, PyArray_ArgSortFunc *argsort,
     it = (PyArrayIterObject *)PyArray_IterAllButAxis((PyObject *)op, &axis);
     rit = (PyArrayIterObject *)PyArray_IterAllButAxis((PyObject *)rop, &axis);
     if (it == NULL || rit == NULL) {
+        ret = -1;
         goto fail;
     }
     size = it->size;
@@ -978,6 +980,7 @@ _new_argsortlike(PyArrayObject *op, int axis, PyArray_ArgSortFunc *argsort,
     if (needcopy) {
         valbuffer = PyDataMem_NEW(N * elsize);
         if (valbuffer == NULL) {
+            ret = -1;
             goto fail;
         }
     }
@@ -985,6 +988,7 @@ _new_argsortlike(PyArrayObject *op, int axis, PyArray_ArgSortFunc *argsort,
     if (needidxbuffer) {
         idxbuffer = (npy_intp *)PyDataMem_NEW(N * sizeof(npy_intp));
         if (idxbuffer == NULL) {
+            ret = -1;
             goto fail;
         }
     }
diff --git a/numpy/core/tests/test_item_selection.py b/numpy/core/tests/test_item_selection.py
index f3e7701d4..5e9cadd8f 100644
--- a/numpy/core/tests/test_item_selection.py
+++ b/numpy/core/tests/test_item_selection.py
@@ -68,6 +68,24 @@ class TestTake(TestCase):
         k = b'\xc3\xa4'.decode("UTF8")
         assert_raises(ValueError, d.take, 5, mode=k)
 
+    def test_empty_partition(self):
+        # In reference to github issue #6530
+        a_original = np.array([0, 2, 4, 6, 8, 10])
+        a = a_original.copy()
+
+        # An empty partition should be a successful no-op
+        a.partition(np.array([], dtype=np.int16))
+
+        assert_array_equal(a, a_original)
+
+    def test_empty_argpartition(self):
+            # In reference to github issue #6530
+            a = np.array([0, 2, 4, 6, 8, 10])
+            a = a.argpartition(np.array([], dtype=np.int16))
+
+            b = np.array([0, 1, 2, 3, 4, 5])
+            assert_array_equal(a, b)
+
 
 if __name__ == "__main__":
     run_module_suite()
diff --git a/numpy/core/tests/test_regression.py b/numpy/core/tests/test_regression.py
index 3aba71463..ac34cfa53 100644
--- a/numpy/core/tests/test_regression.py
+++ b/numpy/core/tests/test_regression.py
@@ -2173,5 +2173,9 @@ class TestRegression(TestCase):
         after = sys.getrefcount(a)
         assert_equal(before, after)
 
+    def test_empty_percentile(self):
+        # gh-6530 / gh-6553
+        assert_array_equal(np.percentile(np.arange(10), []), np.array([]))
+
 if __name__ == "__main__":
     run_module_suite()