How to use the Android NDK to build Arm NN

• Introduction
• Download the Android NDK and make a standalone toolchain
• Build the Boost C++ libraries
• Build the Compute Library
• Build Google's Protobuf library
• Download TensorFlow
• Build Arm NN
• Build Standalone Sample Dynamic Backend
• Run the Arm NN unit tests on an Android device

Introduction

These are step by step instructions for using the Android NDK to build Arm NN. They have been tested on a clean install of Ubuntu 16.04, and should also work with other OS versions. The instructions show how to build the Arm NN core library and the optional TensorFlow parser. All downloaded or generated files will be saved inside the ~/armnn-devenv directory.

Note: We are currently in the process of removing boost as a dependency to Arm NN. This process is finished for everything apart from our unit tests. This means you don't need boost to build and use Arm NN but you need it to execute our unit tests. Boost will soon be removed from Arm NN entirely. We also are deprecating support for Tensorflow parsers in 21.02. This will be removed in 21.05.

Download the Android NDK and make a standalone toolchain

• Download the Android NDK from the official website:

  mkdir -p ~/armnn-devenv/toolchains
  cd ~/armnn-devenv/toolchains
  # For Mac OS, change the NDK download link accordingly.
  wget https://dl.google.com/android/repository/android-ndk-r20b-linux-x86_64.zip
  unzip android-ndk-r20b-linux-x86_64.zip
  export NDK=~/armnn-devenv/android-ndk-r20b
  export NDK_TOOLCHAIN_ROOT=$NDK/toolchains/llvm/prebuilt/linux-x86_64
  export PATH=$NDK_TOOLCHAIN_ROOT/bin/:$PATH
  
  # You may want to append the above export variables commands to your `~/.bashrc` (or `~/.bash_profile` in Mac OS).

• With the android ndk-20b, you don't need to use the make_standalone_toolchain script to create a toolchain for a specific version of android. Android's current preference is for you to just specify the architecture and operating system while setting the compiler and just use the ndk directory.

Build the Boost C++ libraries

• Download Boost version 1.64:

  mkdir ~/armnn-devenv/boost
  cd ~/armnn-devenv/boost
  wget https://dl.bintray.com/boostorg/release/1.64.0/source/boost_1_64_0.tar.bz2
  tar xvf boost_1_64_0.tar.bz2

• Build:

  (Requires clang if not previously installed: sudo apt-get install clang)

  Note: You can specify the 'Android_API' version you want. For example, if your ANDROID_API is 27 then the compiler will be aarch64-linux-android27-clang++.

  echo "using clang : arm : aarch64-linux-android<Android_API>-clang++ ;" > $HOME/armnn-devenv/boost/user-config.jam
  cd ~/armnn-devenv/boost/boost_1_64_0
  ./bootstrap.sh --prefix=$HOME/armnn-devenv/boost/install
  ./b2 install --user-config=$HOME/armnn-devenv/boost/user-config.jam \
   toolset=clang-arm link=static cxxflags=-fPIC \
   --with-test --with-log --with-program_options -j16

Build the Compute Library

• Clone the Compute Library:

  (Requires Git if not previously installed: sudo apt install git)

  cd ~/armnn-devenv
  git clone https://github.com/ARM-software/ComputeLibrary.git

• Checkout ComputeLibrary branch:

  cd ComputeLibrary
  git checkout <branch_name>
  git pull

  For example, if you want to checkout release branch of 20.02:

  git checkout branches/arm_compute_20_02
  git pull

• Build:

  (Requires SCons if not previously installed: sudo apt install scons)

  scons arch=arm64-v8a neon=1 opencl=1 embed_kernels=1 extra_cxx_flags="-fPIC" \
   benchmark_tests=0 validation_tests=0 os=android -j16

Build Google's Protobuf library

• Clone protobuf:

  mkdir ~/armnn-devenv/google
  cd ~/armnn-devenv/google
  git clone https://github.com/google/protobuf.git
  cd protobuf
  git checkout -b v3.12.0 v3.12.0

• Build a native (x86) version of the protobuf libraries and compiler (protoc):

  (Requires cUrl, autoconf, llibtool, and other build dependencies if not previously installed: sudo apt install curl autoconf libtool build-essential g++)

  ./autogen.sh
  mkdir x86_build
  cd x86_build
  ../configure --prefix=$HOME/armnn-devenv/google/x86_pb_install
  make install -j16
  cd ..

• Build the arm64 version of the protobuf libraries:

  mkdir arm64_build
  cd arm64_build
  CC=aarch64-linux-android<Android_API>-clang \
  CXX=aarch64-linux-android<Android_API>-clang++ \
  CFLAGS="-fPIE -fPIC" \
      LDFLAGS="-llog -lz -lc++_static" \
     ../configure --host=aarch64-linux-android \
     --prefix=$HOME/armnn-devenv/google/arm64_pb_install \
     --enable-cross-compile \
     --with-protoc=$HOME/armnn-devenv/google/x86_pb_install/bin/protoc
  make install -j16
  cd ..

Download TensorFlow

• Clone TensorFlow source code:

  cd ~/armnn-devenv/google/
  git clone https://github.com/tensorflow/tensorflow.git
      cd tensorflow/
      git checkout fcc4b966f1265f466e82617020af93670141b009

Build Arm NN

• Clone Arm NN source code:

  cd ~/armnn-devenv/
  git clone https://github.com/ARM-software/armnn.git

• Checkout Arm NN branch:

  cd armnn
  git checkout <branch_name>
  git pull

For example, if you want to checkout release branch of 20.02:

git checkout branches/armnn_20_02
git pull

• Generate TensorFlow protobuf definitions:

  cd ~/armnn-devenv/google/tensorflow
  ~/armnn-devenv/armnn/scripts/generate_tensorflow_protobuf.sh \
   $HOME/armnn-devenv/google/tf_pb $HOME/armnn-devenv/google/x86_pb_install

• Build Arm NN:

  (Requires CMake if not previously installed: sudo apt install cmake)

  mkdir ~/armnn-devenv/armnn/build
  cd ~/armnn-devenv/armnn/build
  CXX=aarch64-linux-android<Android_API>-clang++ \
  CC=aarch64-linux-android<Android_API>-clang \
  CXX_FLAGS="-fPIE -fPIC" \
  cmake .. \
      -DCMAKE_ANDROID_NDK=$NDK \
      -DCMAKE_SYSTEM_NAME=Android \
      -DCMAKE_SYSTEM_VERSION=<Android_API> \
      -DCMAKE_ANDROID_ARCH_ABI=arm64-v8a \
      -DCMAKE_EXE_LINKER_FLAGS="-pie -llog -lz" \
      -DARMCOMPUTE_ROOT=$HOME/armnn-devenv/ComputeLibrary/ \
      -DARMCOMPUTE_BUILD_DIR=$HOME/armnn-devenv/ComputeLibrary/build \
      -DBOOST_ROOT=$HOME/armnn-devenv/boost/install/ \
      -DARMCOMPUTENEON=1 -DARMCOMPUTECL=1 -DARMNNREF=1 \
      -DTF_GENERATED_SOURCES=$HOME/armnn-devenv/google/tf_pb/ -DBUILD_TF_PARSER=1 \
      -DPROTOBUF_ROOT=$HOME/armnn-devenv/google/arm64_pb_install/

To include standalone sample dynamic backend tests, add the argument to enable the tests and the dynamic backend path to the CMake command:

-DSAMPLE_DYNAMIC_BACKEND=1 \
-DDYNAMIC_BACKEND_PATHS=$SAMPLE_DYNAMIC_BACKEND_PATH
# Where $SAMPLE_DYNAMIC_BACKEND_PATH is the path where libArm_SampleDynamic_backend.so library file is pushed

• Run the build

  make -j16

Build Standalone Sample Dynamic Backend

• The sample dynamic backend is located in armnn/src/dynamic/sample

  mkdir build
  cd build

• Use CMake to configure the build environment, update the following script and run it from the armnn/src/dynamic/sample/build directory to set up the Arm NN build:

  #!/bin/bash
  CXX=aarch64-linux-android<Android_API>-clang++ \
  CC=aarch64-linux-android<Android_API>-clang \
  CXX_FLAGS="-fPIE -fPIC" \
  cmake \
  -DCMAKE_SYSTEM_NAME=Android \
  -DCMAKE_CXX_FLAGS=--std=c++14 \
  -DCMAKE_EXE_LINKER_FLAGS="-pie -llog" \
  -DCMAKE_MODULE_LINKER_FLAGS="-llog" \
  -DBOOST_ROOT=$HOME/armnn-devenv/boost/install \
  -DBoost_SYSTEM_LIBRARY=$HOME/armnn-devenv/boost/install/lib/libboost_system.a \
  -DARMNN_PATH=$HOME/armnn-devenv/armnn/build/libarmnn.so ..

• Run the build

  make

Run the Arm NN unit tests on an Android device

• Push the build results to an Android device and make symbolic links for shared libraries: Currently adb version we have used for testing is 1.0.41.

  adb push libarmnnTfParser.so /data/local/tmp/
  adb push libarmnn.so /data/local/tmp/
      adb push libtimelineDecoder.so /data/local/tmp/
  adb push UnitTests /data/local/tmp/
  adb push $NDK/sources/cxx-stl/llvm-libc++/libs/arm64-v8a/libc++_shared.so /data/local/tmp/
  adb push $HOME/armnn-devenv/google/arm64_pb_install/lib/libprotobuf.so /data/local/tmp/libprotobuf.so.24.0.0
  adb shell 'ln -s libprotobuf.so.24.0.0 /data/local/tmp/libprotobuf.so.24'
  adb shell 'ln -s libprotobuf.so.24.0.0 /data/local/tmp/libprotobuf.so'

• Push the files needed for the unit tests (they are a mix of files, directories and symbolic links):

  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/testSharedObject
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/testSharedObject/* /data/local/tmp/src/backends/backendsCommon/test/testSharedObject/
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/testDynamicBackend
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/testDynamicBackend/* /data/local/tmp/src/backends/backendsCommon/test/testDynamicBackend/
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath1
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/backendsTestPath1/* /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath1/
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath2
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/backendsTestPath2/Arm_CpuAcc_backend.so /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath2/
  adb shell ln -s Arm_CpuAcc_backend.so /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath2/Arm_CpuAcc_backend.so.1
  adb shell ln -s Arm_CpuAcc_backend.so.1 /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath2/Arm_CpuAcc_backend.so.1.2
  adb shell ln -s Arm_CpuAcc_backend.so.1.2 /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath2/Arm_CpuAcc_backend.so.1.2.3
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/backendsTestPath2/Arm_GpuAcc_backend.so /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath2/
  adb shell ln -s nothing /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath2/Arm_no_backend.so
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath3
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath5
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/backendsTestPath5/* /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath5/
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath6
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/backendsTestPath6/* /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath6/
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath7
  
  adb shell mkdir -p /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath9
  adb push -p ~/armnn-devenv/armnn/build/src/backends/backendsCommon/test/backendsTestPath9/* /data/local/tmp/src/backends/backendsCommon/test/backendsTestPath9/
  
  adb shell mkdir -p /data/local/tmp/src/backends/dynamic/reference
  adb push -p ~/armnn-devenv/armnn/build/src/backends/dynamic/reference/Arm_CpuRef_backend.so /data/local/tmp/src/backends/dynamic/reference/
  
  # If the standalone sample dynamic tests are enabled, also push libArm_SampleDynamic_backend.so library file to the folder specified as $SAMPLE_DYNAMIC_BACKEND_PATH when Arm NN is built.
  # This is the example when $SAMPLE_DYNAMIC_BACKEND_PATH is specified as /data/local/tmp/dynamic/sample/:
  
  adb shell mkdir -p /data/local/tmp/dynamic/sample/
  adb push -p ${WORKING_DIR}/armnn/src/dynamic/sample/build/libArm_SampleDynamic_backend.so /data/local/tmp/dynamic/sample/

• Run Arm NN unit tests:

  adb shell 'LD_LIBRARY_PATH=/data/local/tmp:/vendor/lib64:/vendor/lib64/egl /data/local/tmp/UnitTests'

  If libarmnnUtils.a is present in ~/armnn-devenv/armnn/build/ and the unit tests run without failure then the build was successful.