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Add pybindings for host buffer size functions (#213)
The purpose is to make the host-side buffer size functions available in a Python environment. Also adds pytest-based checks for the new python glue. Check README files for more details.
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lines changed

‎CMakeLists.txt‎

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@@ -1,5 +1,5 @@
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#
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# SPDX-FileCopyrightText: Copyright 2010-2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
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# SPDX-FileCopyrightText: Copyright 2010-2023, 2026 Arm Limited and/or its affiliates <open-source-office@arm.com>
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#
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# SPDX-License-Identifier: Apache-2.0
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#
@@ -19,7 +19,7 @@
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cmake_minimum_required(VERSION 3.15.6)
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set(CMSIS_OPTIMIZATION_LEVEL "-Ofast" CACHE STRING "Compiler optimization level.")
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project(CMSISNN)
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project(CMSISNN C CXX)
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add_library(cmsis-nn STATIC)
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@@ -28,3 +28,87 @@ target_compile_options(cmsis-nn PRIVATE ${CMSIS_OPTIMIZATION_LEVEL})
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target_include_directories(cmsis-nn PUBLIC "Include")
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add_subdirectory(Source)
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option(CMSISNN_BUILD_PYBIND "Build pybind11 Python module for CMSIS-NN helpers" OFF)
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if(CMSISNN_BUILD_PYBIND)
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# Add shared library for testing bindings with ctest
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add_library(cmsis-nn-shared SHARED
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$<TARGET_PROPERTY:cmsis-nn,SOURCES>
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)
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set_target_properties(cmsis-nn-shared PROPERTIES OUTPUT_NAME cmsis-nn)
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target_include_directories(cmsis-nn-shared PRIVATE
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$<TARGET_PROPERTY:cmsis-nn,INCLUDE_DIRECTORIES>
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)
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target_compile_options(cmsis-nn-shared PRIVATE ${CMSIS_OPTIMIZATION_LEVEL})
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find_package(Python3 COMPONENTS Interpreter Development REQUIRED)
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find_package(pybind11 CONFIG QUIET)
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if(pybind11_FOUND)
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message(STATUS "Found pybind11 via CMake package")
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else()
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execute_process(
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COMMAND ${Python3_EXECUTABLE} -c "import pybind11; print(pybind11.get_include())"
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OUTPUT_VARIABLE PYBIND11_INCLUDE_DIR
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OUTPUT_STRIP_TRAILING_WHITESPACE
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)
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endif()
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if(PYBIND11_INCLUDE_DIR)
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message(STATUS "pybind11 include: ${PYBIND11_INCLUDE_DIR}")
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elseif(NOT pybind11_FOUND)
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message(FATAL_ERROR "pybind11 not found. Install pybind11 or set CMSISNN_BUILD_PYBIND=OFF.")
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endif()
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add_library(cmsis_nn MODULE
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Source/Bindings/arm_py_module.cpp
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Source/Bindings/arm_py_backend.cpp
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Source/Bindings/arm_py_avgpool_buffer_size.cpp
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Source/Bindings/arm_py_conv_buffer_size.cpp
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Source/Bindings/arm_py_depthwise_conv_buffer_size.cpp
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Source/Bindings/arm_py_fully_connected_buffer_size.cpp
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Source/Bindings/arm_py_svdf_buffer_size.cpp
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Source/Bindings/arm_py_transpose_conv_buffer_size.cpp
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)
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set_target_properties(cmsis_nn PROPERTIES PREFIX "")
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if(Python3_INCLUDE_DIRS)
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target_include_directories(cmsis_nn PRIVATE
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${Python3_INCLUDE_DIRS}
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)
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else()
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execute_process(
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COMMAND ${Python3_EXECUTABLE} -c "import sysconfig; print(sysconfig.get_paths()['include'])"
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OUTPUT_VARIABLE PYTHON_INCLUDE_DIR
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OUTPUT_STRIP_TRAILING_WHITESPACE
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)
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target_include_directories(cmsis_nn PRIVATE
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${PYTHON_INCLUDE_DIR}
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)
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endif()
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target_link_libraries(cmsis_nn PRIVATE cmsis-nn)
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target_include_directories(cmsis_nn PRIVATE
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${CMAKE_CURRENT_SOURCE_DIR}/Include
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)
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if(pybind11_FOUND)
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target_link_libraries(cmsis_nn PRIVATE pybind11::headers)
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else()
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target_include_directories(cmsis_nn PRIVATE
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${PYBIND11_INCLUDE_DIR}
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)
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endif()
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target_compile_options(cmsis_nn PRIVATE ${CMSIS_OPTIMIZATION_LEVEL})
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# Put the built .so into the python package directory inside the wheel
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install(TARGETS cmsis_nn
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LIBRARY DESTINATION cmsis_nn
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RUNTIME DESTINATION cmsis_nn
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)
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endif()

‎README.md‎

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@@ -95,6 +95,47 @@ cmake .. -DCMAKE_TOOLCHAIN_FILE=</path/to/ethos-u-core-platform>/cmake/toolchain
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cmake .. -DCMAKE_TOOLCHAIN_FILE=</path/to/ethos-u-core-platform>/cmake/toolchain/armclang.cmake -DTARGET_CPU=cortex-m3
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```
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## Python bindings (optional)
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The Python helpers are built as a `cmsis_nn` extension module using pybind11.
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The purpose is to expose the CMSIS-NN host buffer size getter functions so they can be accessed and used from Python.
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Build the extension with CMake:
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```
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cmake -S . -B build -DCMSISNN_BUILD_PYBIND=ON
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cmake --build build
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```
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This produces a `cmsis_nn` shared library in the build tree. For a pip-installable wheel, use:
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```
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pip wheel . -w dist
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pip install dist/cmsis_nn-*.whl
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```
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Example usage:
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```
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import cmsis_nn
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backend = cmsis_nn.Backend.MVE
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buf_size = cmsis_nn.convolve_wrapper_buffer_size(
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backend,
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cmsis_nn.DataType.A8W8,
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input_nhwc=[1, 8, 8, 16],
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filter_nhwc=[8, 3, 3, 16],
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output_nhwc=[1, 6, 6, 8],
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padding_hw=[0, 0],
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stride_hw=[1, 1],
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dilation_hw=[1, 1],
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)
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```
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Optionally backend can be derived, e.g.:
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```
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backend = cmsis_nn.resolve_backend(cmsis_nn.CortexM.M55)
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```
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98139
### Compiler Options
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Default optimization level is set at Ofast. This can be overwritten with CMake on command line by using <nobr>*"-DCMSIS_OPTIMIZATION_LEVEL"*</nobr>. Please change according to project needs.
100141
Just bear in mind this can impact performance. With only optimization level -O0, *ARM_MATH_AUTOVECTORIZE* needs to be defined for processors with Helium

‎Source/Bindings/arm_py_avgpool_buffer_size.cpp‎

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/*
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* SPDX-FileCopyrightText: Copyright 2026 Arm Limited and/or its affiliates <open-source-office@arm.com>
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
13+
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
16+
* limitations under the License.
17+
*/
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/* ----------------------------------------------------------------------
20+
* Project: CMSIS NN Library
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* Title: arm_py_avgpool_buffer_size.cpp
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* Description: Average pooling buffer size pybinds (optional Python module)
23+
*
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* $Date: 23 Feb 2026
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* $Revision: V.1.0.0
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*
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* Target : Host/Python
28+
* -------------------------------------------------------------------- */
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#include <sstream>
31+
32+
#include "arm_py_common.hpp"
33+
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extern "C" {
35+
#include "arm_nnfunctions.h"
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}
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namespace py = pybind11;
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void avgpool_buffer_size(py::module_ &m)
41+
{
42+
m.def(
43+
"avgpool_buffer_size",
44+
[](Backend backend, DataType data_type, int32_t dim_dst_width, int32_t ch_src) -> int32_t {
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switch (data_type)
46+
{
47+
case DataType::A8W8:
48+
switch (backend)
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{
50+
case Backend::MVE:
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return arm_avgpool_s8_get_buffer_size_mve(dim_dst_width, ch_src);
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case Backend::DSP:
53+
return arm_avgpool_s8_get_buffer_size_dsp(dim_dst_width, ch_src);
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case Backend::SCALAR:
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return arm_avgpool_s8_get_buffer_size(dim_dst_width, ch_src);
56+
}
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break;
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case DataType::A16W8:
59+
switch (backend)
60+
{
61+
case Backend::MVE:
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return arm_avgpool_s16_get_buffer_size_mve(dim_dst_width, ch_src);
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case Backend::DSP:
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return arm_avgpool_s16_get_buffer_size_dsp(dim_dst_width, ch_src);
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case Backend::SCALAR:
66+
return arm_avgpool_s16_get_buffer_size(dim_dst_width, ch_src);
67+
}
68+
break;
69+
}
70+
std::ostringstream msg;
71+
msg << "invalid Backend/DataType combination: backend=" << static_cast<int>(backend)
72+
<< " data_type=" << static_cast<int>(data_type);
73+
throw py::value_error(msg.str());
74+
},
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py::arg("backend"),
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py::arg("data_type"),
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py::arg("dim_dst_width"),
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py::arg("ch_src"));
79+
}

‎Source/Bindings/arm_py_backend.cpp‎

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/*
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* SPDX-FileCopyrightText: Copyright 2026 Arm Limited and/or its affiliates <open-source-office@arm.com>
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
13+
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
16+
* limitations under the License.
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*/
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/* ----------------------------------------------------------------------
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* Project: CMSIS NN Library
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* Title: arm_py_backend.cpp
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* Description: Backend resolution helpers for optional Python module
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*
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* $Date: 23 Feb 2026
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* $Revision: V.1.0.0
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*
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* Target : Host/Python
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* -------------------------------------------------------------------- */
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#include "arm_py_common.hpp"
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namespace py = pybind11;
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void backend_helpers(py::module_ &m)
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{
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py::enum_<CortexM>(m, "CortexM")
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.value("M0", CortexM::M0)
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.value("M0PLUS", CortexM::M0PLUS)
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.value("M3", CortexM::M3)
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.value("M4", CortexM::M4)
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.value("M7", CortexM::M7)
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.value("M23", CortexM::M23)
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.value("M33", CortexM::M33)
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.value("M35P", CortexM::M35P)
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.value("M55", CortexM::M55)
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.value("M85", CortexM::M85);
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48+
m.def(
49+
"resolve_backend",
50+
[](CortexM core) -> Backend {
51+
switch (core)
52+
{
53+
case CortexM::M55:
54+
case CortexM::M85:
55+
return Backend::MVE;
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case CortexM::M4:
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case CortexM::M7:
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case CortexM::M33:
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case CortexM::M35P:
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return Backend::DSP;
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case CortexM::M0:
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case CortexM::M0PLUS:
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case CortexM::M3:
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case CortexM::M23:
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return Backend::SCALAR;
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}
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throw py::value_error("unsupported Cortex-M core");
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},
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py::arg("core"));
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}

‎Source/Bindings/arm_py_common.hpp‎

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/*
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* SPDX-FileCopyrightText: Copyright 2026 Arm Limited and/or its affiliates <open-source-office@arm.com>
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
8+
* You may obtain a copy of the License at
9+
*
10+
* www.apache.org/licenses/LICENSE-2.0
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*
12+
* Unless required by applicable law or agreed to in writing, software
13+
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
14+
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15+
* See the License for the specific language governing permissions and
16+
* limitations under the License.
17+
*/
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/* ----------------------------------------------------------------------
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* Project: CMSIS NN Library
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* Title: arm_py_common.hpp
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* Description: Common helpers and types for optional Python module
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*
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* $Date: 23 Feb 2026
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* $Revision: V.1.0.0
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*
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* Target : Host/Python
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* -------------------------------------------------------------------- */
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#ifndef ARM_PY_BINDINGS_COMMON_HPP
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#define ARM_PY_BINDINGS_COMMON_HPP
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#include <array>
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#include <pybind11/pybind11.h>
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#include <pybind11/stl.h>
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extern "C" {
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#include "arm_nn_types.h"
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}
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namespace py = pybind11;
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enum class Backend
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{
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MVE,
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DSP,
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SCALAR,
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};
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enum class DataType
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{
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A8W4,
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A8W8,
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A16W8,
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};
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enum class CortexM
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{
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M0,
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M0PLUS,
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M3,
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M4,
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M7,
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M23,
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M33,
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M35P,
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M55,
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M85,
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};
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static inline cmsis_nn_dims make_dims(const std::array<int32_t, 4> &nhwc)
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{
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cmsis_nn_dims d;
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d.n = nhwc[0];
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d.h = nhwc[1];
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d.w = nhwc[2];
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d.c = nhwc[3];
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return d;
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}
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#endif // ARM_PY_BINDINGS_COMMON_HPP

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