Consider the buffer offset when creating a view on ndarray

CHANGELOG.md

@@ -60,6 +60,7 @@ Also, that release drops support for Python 3.9, making Python 3.10 the minimum
 * Suppressed a potential deprecation warning triggered during import of the `dpctl.tensor` module [#2709](https://github.com/IntelPython/dpnp/pull/2709)
 * Corrected a phonetic spelling issue due to incorrect using of `a nd` in docstrings [#2719](https://github.com/IntelPython/dpnp/pull/2719)
 * Resolved an issue causing `dpnp.linspace` to return an incorrect output shape when inputs were passed as arrays [#2712](https://github.com/IntelPython/dpnp/pull/2712)
+* Resolved an issue where `dpnp` always returns the base allocation pointer, when the view start is expected [#2651](https://github.com/IntelPython/dpnp/pull/2651)
 
 ### Security
 

dpnp/dpnp_array.py

@@ -98,6 +98,7 @@ def __init__(
             # or as USM memory allocation
             if isinstance(buffer, dpnp_array):
                 buffer = buffer.get_array()
+                offset += buffer._element_offset
 
             if dtype is None and hasattr(buffer, "dtype"):
                 dtype = buffer.dtype

dpnp/dpnp_iface_indexing.py

@@ -721,23 +721,21 @@ def diagonal(a, offset=0, axis1=0, axis2=1):
     a_straides = a.strides
     n, m = a_shape[-2:]
     st_n, st_m = a_straides[-2:]
-    # pylint: disable=W0212
-    a_element_offset = a.get_array()._element_offset
 
     # Compute shape, strides and offset of the resulting diagonal array
     # based on the input offset
     if offset == 0:
         out_shape = a_shape[:-2] + (min(n, m),)
         out_strides = a_straides[:-2] + (st_n + st_m,)
-        out_offset = a_element_offset
+        out_offset = 0
     elif 0 < offset < m:
         out_shape = a_shape[:-2] + (min(n, m - offset),)
         out_strides = a_straides[:-2] + (st_n + st_m,)
-        out_offset = a_element_offset + st_m * offset
+        out_offset = st_m * offset
     else:
         out_shape = a_shape[:-2] + (0,)
         out_strides = a_straides[:-2] + (1,)
-        out_offset = a_element_offset
+        out_offset = 0
 
     return dpnp_array(
         out_shape, buffer=a, strides=out_strides, offset=out_offset

dpnp/tests/test_arraycreation.py

@@ -268,6 +268,16 @@ def test_linalg_trace(self, dtype, offset):
         expected = numpy.linalg.trace(a, offset=offset, dtype=dtype)
         assert_equal(result, expected)
 
+    @pytest.mark.parametrize("offset", [-1, 0, 1])
+    def test_ndarray_offset(self, offset):
+        ia = dpnp.arange(8, dtype=dpnp.uint8).reshape((2, 2, 2))
+        ia = dpnp.ndarray((2, 2), buffer=ia, offset=1)
+        a = ia.asnumpy()
+
+        result = dpnp.linalg.trace(ia, offset=offset)
+        expected = numpy.linalg.trace(a, offset=offset)
+        assert_equal(result, expected)
+
 
 @pytest.mark.parametrize(
     "func, args",

dpnp/tests/test_memory.py

@@ -31,3 +31,14 @@ def test_ndarray_from_data(self):
         a = dpnp.empty(5)
         b = dpnp.ndarray(a.shape, buffer=a.data)
         assert b.data.ptr == a.data.ptr
+
+    def test_view_non_zero_offset(self):
+        n, m = 2, 8
+        plane = n * m
+
+        a = dpnp.empty(4 * plane)
+        sl = a[plane:]  # non-zero offset view
+
+        pl = dpnp.ndarray((n, m), dtype=a.dtype, buffer=sl)
+        assert pl.data.ptr == sl.data.ptr
+        assert a.data.ptr != sl.data.ptr