Adds test_tensor_diff with tests for basic diff and axis keyword

Author: ndgrigorian

dpctl/tests/test_tensor_diff.py

@@ -0,0 +1,81 @@
+#                       Data Parallel Control (dpctl)
+#
+#  Copyright 2020-2024 Intel Corporation
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+import pytest
+
+import dpctl.tensor as dpt
+from dpctl.tests.helper import get_queue_or_skip, skip_if_dtype_not_supported
+
+_all_dtypes = [
+    "?",
+    "i1",
+    "u1",
+    "i2",
+    "u2",
+    "i4",
+    "u4",
+    "i8",
+    "u8",
+    "f2",
+    "f4",
+    "f8",
+    "c8",
+    "c16",
+]
+
+
+@pytest.mark.parametrize("dt", _all_dtypes)
+def test_diff_basic(dt):
+    q = get_queue_or_skip()
+    skip_if_dtype_not_supported(dt, q)
+
+    x = dpt.asarray([9, 12, 7, 17, 10, 18, 15, 9, 8, 8], dtype=dt, sycl_queue=q)
+    res = dpt.diff(x)
+    op = dpt.not_equal if x.dtype is dpt.bool else dpt.subtract
+    expected_res = op(x[1:], x[:-1])
+    if dpt.dtype(dt).kind in "fc":
+        assert dpt.allclose(res, expected_res)
+    else:
+        assert dpt.all(res == expected_res)
+
+    res = dpt.diff(x, n=5)
+    expected_res = x
+    for _ in range(5):
+        expected_res = op(expected_res[1:], expected_res[:-1])
+    if dpt.dtype(dt).kind in "fc":
+        assert dpt.allclose(res, expected_res)
+    else:
+        assert dpt.all(res == expected_res)
+
+
+def test_diff_axis():
+    get_queue_or_skip()
+
+    x = dpt.tile(
+        dpt.asarray([9, 12, 7, 17, 10, 18, 15, 9, 8, 8], dtype="i4"), (3, 4, 1)
+    )
+    x[:, ::2, :] = 0
+    res = dpt.diff(x, n=1, axis=1)
+    expected_res = dpt.subtract(x[:, 1:, :], x[:, :-1, :])
+    assert dpt.all(res == expected_res)
+
+    res = dpt.diff(x, n=3, axis=1)
+    expected_res = x
+    for _ in range(3):
+        expected_res = dpt.subtract(
+            expected_res[:, 1:, :], expected_res[:, :-1, :]
+        )
+    assert dpt.all(res == expected_res)