add test_sycl_usm test to use copy_from_device

Author: oleksandr-pavlyk

dpctl/tests/test_sycl_usm.py

@@ -475,3 +475,24 @@ def test_memory_construction_from_other_memory_objects():
     m3 = MemoryUSMShared(m_de, copy=True)
     assert bytes(m1) == bytes(m_sh)
     assert bytes(m2) == bytes(m3)
+
+
+def test_memory_copy_between_contexts():
+    try:
+        q = dpctl.SyclQueue("cpu")
+    except dpctl.SyclQueueCreationError:
+        pytest.skip("CPU queue could not be created")
+    d = q.sycl_device
+    n = d.max_compute_units
+    n_half = n // 2
+    d0, d1 = d.create_sub_devices(partition=[n_half, n - n_half])
+    q0 = dpctl.SyclQueue(d0)
+    q1 = dpctl.SyclQueue(d1)
+    m0 = MemoryUSMDevice(256, queue=q0)
+    m1 = MemoryUSMDevice(256, queue=q1)
+    host_buf = b"abcd" * 64
+    m0.copy_from_host(host_buf)
+    m1.copy_from_device(m0)
+    copy_buf = bytearray(256)
+    m1.copy_to_host(copy_buf)
+    assert host_buf == copy_buf