refinements

Author: flexatone

src/methods.c

@@ -1466,14 +1466,20 @@ map_object(PyObject *Py_UNUSED(m), PyObject *args, PyObject *kwargs)
     int has_big_int = 0;
     int needs_object = 0;
 
-    for (npy_intp i = 0; i < n; i++) {
+    // 1D: hoist the base pointer and element stride and walk a running pointer, rather
+    // than recomputing PyArray_GETPTR1 each iteration. For a contiguous array the stride
+    // is the itemsize (direct indexing into the flat buffer); a strided slice still works.
+    char *p = (char*)PyArray_DATA(array);
+    npy_intp stride = PyArray_STRIDES(array)[0];
+
+    for (npy_intp i = 0; i < n; i++, p += stride) {
         PyObject *elem;
         if (is_object) {
-            elem = *(PyObject**)PyArray_GETPTR1(array, i);
+            elem = *(PyObject**)p;
             Py_INCREF(elem);
         }
         else {
-            elem = PyArray_ToScalar(PyArray_GETPTR1(array, i), array);
+            elem = PyArray_ToScalar(p, array);
             if (elem == NULL) {
                 goto fail;
             }

test/test_map_object.py

@@ -119,6 +119,19 @@ def test_map_object_empty(self) -> None:
         post = self._check(np.array([], dtype=np.float64), lambda x: str(x))
         self.assertEqual(len(post), 0)
 
+    def test_map_object_strided_non_contiguous(self) -> None:
+        # a strided slice (non-contiguous) must be walked correctly by the running pointer
+        base = np.array([1.0, 99.0, 2.0, 99.0, 3.0])
+        strided = base[::2]
+        self.assertFalse(strided.flags['C_CONTIGUOUS'])
+        post = self._check(strided, lambda x: str(x))
+        self.assertEqual(post.tolist(), ['1.0', '2.0', '3.0'])
+
+    def test_map_object_strided_object(self) -> None:
+        arr = np.array(['a', 'X', 'bb', 'X', 'ccc'], dtype=object)[::2]
+        post = self._check(arr, lambda x: len(x))
+        self.assertEqual(post.tolist(), [1, 2, 3])
+
     def test_map_object_propagates_exception(self) -> None:
         def bad(x):
             raise ValueError('boom')