Fix issue with 'at' method when indices are all slice objects

2 files changed, 24 insertions, 2 deletions

diff --git a/numpy/core/src/multiarray/mapping.c b/numpy/core/src/multiarray/mapping.c
index a7c1c854c..d8af546a3 100644
--- a/numpy/core/src/multiarray/mapping.c
+++ b/numpy/core/src/multiarray/mapping.c
@@ -1663,7 +1663,9 @@ PyArray_MapIterReset(PyArrayMapIterObject *mit)
 
     mit->index = 0;
 
-    copyswap = PyArray_DESCR(mit->iters[0]->ao)->f->copyswap;
+    if (mit->numiter > 0) {
+        copyswap = PyArray_DESCR(mit->iters[0]->ao)->f->copyswap;
+    }
 
     if (mit->subspace != NULL) {
         memcpy(coord, mit->bscoord, sizeof(npy_intp)*PyArray_NDIM(mit->ait->ao));
@@ -1714,7 +1716,11 @@ PyArray_MapIterNext(PyArrayMapIterObject *mit)
     if (mit->index >= mit->size) {
         return;
     }
-    copyswap = PyArray_DESCR(mit->iters[0]->ao)->f->copyswap;
+
+    if (mit->numiter > 0) {
+        copyswap = PyArray_DESCR(mit->iters[0]->ao)->f->copyswap;
+    }
+
     /* Sub-space iteration */
     if (mit->subspace != NULL) {
         PyArray_ITER_NEXT(mit->subspace);
diff --git a/numpy/core/tests/test_ufunc.py b/numpy/core/tests/test_ufunc.py
index 5b3b1ce02..8aac509a6 100644
--- a/numpy/core/tests/test_ufunc.py
+++ b/numpy/core/tests/test_ufunc.py
@@ -939,6 +939,22 @@ class TestUfunc(TestCase):
               [21,  22, 23],
               [24,  25, 26]]])
 
+        a = np.arange(27).reshape(3,3,3)
+        b = np.array([100,200,300])
+        np.add.at(a, (slice(None), slice(None), slice(None)), b)
+        assert_equal(a,
+            [[[100,201,302], 
+              [103,204,305], 
+              [106,207,308]],
+              
+             [[109,210,311],  
+              [112,213,314], 
+              [115,216,317]],
+
+             [[118,219,320],
+              [121,222,323],
+              [124,225,326]]])
+
         a = np.arange(10)
         np.negative.at(a, [2,5,2])
         assert_equal(a, [0, 1, 2, 3, 4, -5, 6, 7, 8, 9])