# How to use the Android NDK to build ArmNN

*  [Introduction](#introduction)
*  [Download the Android NDK and make a standalone toolchain](#downloadNDK)
*  [Build the Boost C++ libraries](#buildBoost)
*  [Build the Compute Library](#buildCL)
*  [Build Google's Protobuf library](#buildProtobuf)
*  [Download TensorFlow](#downloadTF)
*  [Build ArmNN](#buildArmNN)
*  [Run ArmNN UnitTests on an Android device](#runArmNNUnitTests)


#### <a name="introduction">Introduction</a>
These are step by step instructions for using the Android NDK to build ArmNN.
They have been tested on a clean install of Ubuntu 18.04, and should also work with other OS versions.
The instructions show how to build the ArmNN core library and the optional TensorFlow parser.
All downloaded or generated files will be saved inside the `~/armnn-devenv` directory.

#### <a name="downloadNDK">Download the Android NDK and make a standalone toolchain</a>

* Download the Android NDK from [the official website](https://developer.android.com/ndk/downloads/index.html):

     ```bash
     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.

#### <a name="buildBoost">Build the Boost C++ libraries</a>

* Download Boost version 1.64:

   ```bash
   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`)
	```bash
	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
    ```
 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++.

#### <a name="buildCL">Build the Compute Library</a>
* Clone the Compute Library:

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

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

* Checkout ComputeLibrary branch:
        ```bash
        cd ComputeLibrary
        git checkout <branch_name>
        git pull
        ```
        For example, if you want to checkout release branch of 20.02:
        ```bash
        git checkout branches/arm_compute_20_02
        git pull
        ```

* Build:

	(Requires SCons if not previously installed: `sudo apt install scons`)
	```bash
	scons arch=arm64-v8a neon=1 opencl=1 embed_kernels=1 extra_cxx_flags="-fPIC" \
	 benchmark_tests=0 validation_tests=0 os=android -j16
	```

#### <a name="buildProtobuf">Build Google's Protobuf library</a>

* Clone protobuf:
	```bash
	mkdir ~/armnn-devenv/google
	cd ~/armnn-devenv/google
	git clone https://github.com/google/protobuf.git
	cd protobuf
	git checkout -b v3.5.2 v3.5.2
	```

* 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++`)

	```bash
	./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:

   ```bash
 	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 ..
	```

#### <a name="downloadTF">Download TensorFlow</a>
* Clone TensorFlow source code:

	```bash
	cd ~/armnn-devenv/google/
	git clone https://github.com/tensorflow/tensorflow.git
        cd tensorflow/
        git checkout 590d6eef7e91a6a7392c8ffffb7b58f2e0c8bc6b
	```

	You need tensorflow/contrib/makefile/tf_proto_files.txt from TensorFlow to generate TensorFlow protobuf definitions. This file is not available in TensorFlow master branch.

#### <a name="buildArmNN">Build ArmNN</a>

* Clone ArmNN source code:

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

* Checkout ArmNN branch:

        ```bash
        cd armnn
        git checkout <branch_name>
        git pull
        ```

        For example, if you want to checkout release branch of 20.02:
        ```bash
        git checkout branches/armnn_20_02
        git pull
        ```

* Generate TensorFlow protobuf definitions:

	```bash
	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 ArmNN:

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

	```bash
	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:

    ```bash
    -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
    ```bash
    make -j16
    ```

#### <a name="buildStandaloneBackend">Build Standalone Sample Dynamic Backend</a>
* The sample dynamic backend is located in armnn/src/dynamic/sample
    ```bash
    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 armNN build:
    ```bash
    #!/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
    ```bash
    make
    ```

#### <a name="runArmNNUnitTests">Run the ArmNN unit tests on an Android device</a>


* 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.

	```bash
	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.15.0.1
	adb shell 'ln -s libprotobuf.so.15.0.1 /data/local/tmp/libprotobuf.so.15'
	adb shell 'ln -s libprotobuf.so.15.0.1 /data/local/tmp/libprotobuf.so'
	```

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

	```bash
	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 ArmNN is built.
	This is the example when $SAMPLE_DYNAMIC_BACKEND_PATH is specified as /data/local/tmp/dynamic/sample/:

	```bash
	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 ArmNN unit tests:

	```bash
	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.