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PaddlePaddle Compiling Guide for iOS

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This tutorial will walk you through cross compiling the PaddlePaddle library for iOS from the source in MacOS.

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Preparation

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Apple provides Xcode for cross-compiling and IDE for iOS development. Download from App store or here. To verify your installation, run command as follows

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$ xcodebuild -version
+Xcode 9.0
+Build version 9A235
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Cross-compiling configurations

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PaddlePaddle provides cross-compiling toolchain configuration documentation cmake/cross_compiling/ios.cmake, which has some default settings for frequently used compilers.

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There are some mandatory environment variables need to be set before cross compiling PaddlePaddle for iOS:

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  • CMAKE_SYSTEM_NAME, CMake compiling target platform name, has to be iOS. PaddlePaddle CMake will compile all the third party dependencies and enforce some parameters (WITH_C_API=ON、WITH_GPU=OFF、WITH_AVX=OFF、WITH_PYTHON=OFF、WITH_RDMA=OFF) when this variable is set with value iOS.
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  • WITH_C_API, Whether to compile inference C-API library, has to be ON, since C-API is the only supported interface for inferencing in iOS.
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  • WITH_SWIG_PY, has to be ON. It’s not supported to inference or train via swig in iOS.
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Optional environment variables for iOS are：

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  • IOS_PLATFORM, either OS (default) or SIMULATOR.

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    • OS, build targets ARM-based physical devices like iPhone or iPad.
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    • SIMULATOR, build targets x86 architecture simulators.
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  • IOS_ARCH, target architecture. By default, all architecture types will be compiled. If you need to specify the architecture to compile for, please find valid values for different IOS_PLATFORM settings from the table below:

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    IOS_PLATFORMIOS_ARCH
    OSarmv7, armv7s, arm64
    SIMULATORi386, x86_64
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  • IOS_DEPLOYMENT_TARGET, minimum iOS version to deployment, 7.0 by default.

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  • IOS_ENABLE_BITCODE, whether to enable Bitcode, values can be ON/OFF, ON by default.

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  • IOS_USE_VECLIB_FOR_BLAS, whether to use vecLib framework for BLAS computing. values can be ON/OFF, OFF by default.

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  • IOS_DEVELOPMENT_ROOT, the path to Developer directory, can be explicitly set with your /path/to/platform/Developer. If left blank, PaddlePaddle will automatically pick the Xcode corresponding platform‘s Developer directory based on your IOS_PLATFORM value.

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  • IOS_SDK_ROOT, the path to SDK root, can be explicitly set with your /path/to/platform/Developer/SDKs/SDK. if left black, PaddlePaddle will pick the latest SDK in the directory of IOS_DEVELOPMENT_ROOT.

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other settings：

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  • USE_EIGEN_FOR_BLAS, whether to use Eigen for matrix computing. effective when IOS_USE_VECLIB_FOR_BLAS=OFF. Values can be ON/OFF, OFF by default.
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  • HOST_C/CXX_COMPILER, host C/C++ compiler. Uses value from environment variable CC/CXX by default or cc/c++ if CC/CXX doesn’t exist.
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some typical cmake configurations:

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cmake -DCMAKE_SYSTEM_NAME=iOS \
+      -DIOS_PLATFORM=OS \
+      -DIOS_ARCH="armv7;arm64" \
+      -DIOS_ENABLE_BITCODE=ON \
+      -DIOS_USE_VECLIB_FOR_BLAS=ON \
+      -DCMAKE_INSTALL_PREFIX=your/path/to/install \
+      -DWITH_C_API=ON \
+      -DWITH_TESTING=OFF \
+      -DWITH_SWIG_PY=OFF \
+      ..
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cmake -DCMAKE_SYSTEM_NAME=iOS \
+      -DIOS_PLATFORM=SIMULATOR \
+      -DIOS_ARCH="x86_64" \
+      -DIOS_USE_VECLIB_FOR_BLAS=ON \
+      -DCMAKE_INSTALL_PREFIX=your/path/to/install \
+      -DWITH_C_API=ON \
+      -DWITH_TESTING=OFF \
+      -DWITH_SWIG_PY=OFF \
+      ..
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You can set other compiling parameters for your own need. I.E. if you are trying to minimize the library size, set CMAKE_BUILD_TYPE with MinSizeRel; or if the performance is your concern, set CMAKE_BUILD_TYPE with Release. You can even manipulate the PaddlePaddle compiling procedure by manually set CMAKE_C/CXX_FLAGS values.

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TIPS for a better performance:

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  • set CMAKE_BUILD_TYPE with Release
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  • set IOS_USE_VECLIB_FOR_BLAS with ON
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Compile and install

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After CMake, run following commands, PaddlePaddle will download the compile 3rd party dependencies, compile and install PaddlePaddle inference library.

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$ make
+$ make install
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Please Note: if you compiled PaddlePaddle in the source directory for other platforms, do remove third_party and build directory within the source with rm -rf to ensure that all the 3rd party libraries dependencies and PaddlePaddle is newly compiled with current CMake configuration.

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your/path/to/install directory will have following directories after compile and install:

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  • include, contains all the C-API header files.
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  • lib, contains PaddlePaddle C-API static library.
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  • third_party contains all the 3rd party libraries.
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Please note: if PaddlePaddle library need to support both physical devices and simulators, you will need to compile correspondingly, then merge fat library with lipo

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Now you will have PaddlePaddle library compiled and installed, the fat library can be used in deep learning related iOS APPs. Please refer to C-API documentation for usage guides.

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