From 81db5e5e5b5cbe63d820f80c70f9781109beb6be Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <21087696+oleksandr-pavlyk@users.noreply.github.com>
Date: Mon, 13 Jan 2025 11:00:53 -0600
Subject: [PATCH 1/4] Implement usm_ndarray.__arrray__ method

The property raises TypeError informing user that
implicit conversions from usm_ndarray to numpy.ndarray
are not permitted.

Explicit conversion using `dpctl.tensor.asnumpy` is
advised.

Disallowing implicit conversion prevents `np.asarray(usm_ar)`
from creating an array of 0D usm_ndarray instances, because
using it is very costly due to multitude of short-array transfers
from GPU to host.
---
 dpctl/tensor/_usmarray.pyx | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/dpctl/tensor/_usmarray.pyx b/dpctl/tensor/_usmarray.pyx
index f61651d4b3..150f0b3b65 100644
--- a/dpctl/tensor/_usmarray.pyx
+++ b/dpctl/tensor/_usmarray.pyx
@@ -1552,6 +1552,14 @@ cdef class usm_ndarray:
     def __repr__(self):
         return usm_ndarray_repr(self)
 
+    def __array__(self, dtype=None, copy=None):
+        "NumPy array protocol"
+        raise TypeError(
+            "Implicit conversion to a NumPy array is not allowed. "
+	    "Use `dpctl.tensor.asnumpy` to copy data from this "
+	    "`dpctl.tensor.usm_ndarray` instance to NumPy array"
+	)
+
 
 cdef usm_ndarray _real_view(usm_ndarray ary):
     """

From d34bad946cc828eb0051bfb22357bc641ec00437 Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <21087696+oleksandr-pavlyk@users.noreply.github.com>
Date: Mon, 13 Jan 2025 11:03:36 -0600
Subject: [PATCH 2/4] Add test that np.asarray(usm_ar) raises TypeError

---
 dpctl/tests/test_usm_ndarray_ctor.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/dpctl/tests/test_usm_ndarray_ctor.py b/dpctl/tests/test_usm_ndarray_ctor.py
index 227cd683dc..ccfc655bfc 100644
--- a/dpctl/tests/test_usm_ndarray_ctor.py
+++ b/dpctl/tests/test_usm_ndarray_ctor.py
@@ -2659,3 +2659,12 @@ def test_setitem_copy_as_contig_alignment(dt):
     x[1:, ...] = vals
     assert dpt.all(x[0] == 0)
     assert dpt.all(x[1:, :] == vals)
+
+
+def test_asarray_property():
+    get_queue_or_skip()
+
+    x = dpt.ones(11, dtype="i4")
+
+    with pytest.raises(TypeError):
+        np.asarray(x)

From b6e3afe7e06c0f21b178e66fec4953bc43d52319 Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <21087696+oleksandr-pavlyk@users.noreply.github.com>
Date: Mon, 13 Jan 2025 12:41:51 -0600
Subject: [PATCH 3/4] Record addition of __array__ method change in changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1c0133e63..88936d5dc7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Improved performance of `tensor.cumulative_sum`, `tensor.cumulative_prod`, `tensor.cumulative_logsumexp` as well as performance of boolean indexing [gh-1923](https://github.com/IntelPython/dpctl/pull/1923)
 * Improved performance of `tensor.min`, `tensor.max`, `tensor.logsumexp`, `tensor.reduce_hypot` for floating point type arrays by at least 2x [gh-1932](https://github.com/IntelPython/dpctl/pull/1932)
 * Extended `tensor.asarray` to support objects that implement `__usm_ndarray__` property to be interpreted as `usm_ndarray` objects [gh-1959](https://github.com/IntelPython/dpctl/pull/1959)
+* `dpctl.tensor.usm_ndarray` object disallows implicit conversions to NumPy array [gh-1964](https://github.com/IntelPython/dpctl/pull/1964)
 
 ### Fixed
 

From 8393a759b6942d33ebc09beb690b2bd0b97da68d Mon Sep 17 00:00:00 2001
From: Oleksandr Pavlyk <21087696+oleksandr-pavlyk@users.noreply.github.com>
Date: Tue, 14 Jan 2025 08:25:25 -0600
Subject: [PATCH 4/4] Make copy argument of __array__ method keyword-only

---
 dpctl/tensor/_usmarray.pyx | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/dpctl/tensor/_usmarray.pyx b/dpctl/tensor/_usmarray.pyx
index 150f0b3b65..668e17bd79 100644
--- a/dpctl/tensor/_usmarray.pyx
+++ b/dpctl/tensor/_usmarray.pyx
@@ -1552,8 +1552,15 @@ cdef class usm_ndarray:
     def __repr__(self):
         return usm_ndarray_repr(self)
 
-    def __array__(self, dtype=None, copy=None):
-        "NumPy array protocol"
+    def __array__(self, dtype=None, /, *, copy=None):
+        """NumPy's array protocol method to disallow implicit conversion.
+
+	Without this definition, `numpy.asarray(usm_ar)` converts
+	usm_ndarray instance into NumPy array with data type `object`
+	and every element being 0d usm_ndarray.
+
+        https://github.com/IntelPython/dpctl/pull/1384#issuecomment-1707212972
+	"""
         raise TypeError(
             "Implicit conversion to a NumPy array is not allowed. "
 	    "Use `dpctl.tensor.asnumpy` to copy data from this "