usm_memory_host_access.py

#                      Data Parallel Control (dpctl)
#
# Copyright 2020-2025 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.

"""
Demonstrates how USM allocated memory can be accessed from the host in a
Python program.
"""

import dpctl.memory as dpmem

# USM-shared and USM-host pointers are host-accessible,
# meaning they are accessible from Python, therefore
# they implement Pyton buffer protocol

# allocate 1K of USM-shared buffer
ms = dpmem.MemoryUSMShared(1024)

# create memoryview into USM-shared buffer
msv = memoryview(ms)

# populate buffer from host one byte at a type
for i in range(len(ms)):
    ir = i % 256
    msv[i] = ir**2 % 256

mh = dpmem.MemoryUSMHost(64)
mhv = memoryview(mh)

# copy content of block of USM-shared buffer to
# USM-host buffer
mhv[:] = msv[78 : 78 + len(mh)]

print("Byte-values of the USM-host buffer")
print(list(mhv))

# USM-device buffer is not host accessible
md = dpmem.MemoryUSMDevice(16)
try:
    mdv = memoryview(md)
except Exception as e:
    print("")
    print(
        "An expected exception was raised during attempted construction of "
        "memoryview from USM-device memory object."
    )
    print("\t", e)