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torchscript.md

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TorchScript support

Introduction of TorchScript

TorchScript a way to create serializable and optimizable models from PyTorch code. Any TorchScript program can be saved from a Python process and loaded in a process where there is no Python dependency. Check the Introduction to TorchScript for more details.

Build custom ops

Prerequisite

  • Download libtorch from the official website here.

Please note that only Pre-cxx11 ABI and version 1.8.1+ on Linux platform are supported by now.

For previous versions of libtorch, users can find through the issue comment. Libtorch1.8.1+cu111 as an example, extract it, expose Torch_DIR and add the lib path to LD_LIBRARY_PATH as below:

wget https://download.pytorch.org/libtorch/cu111/libtorch-shared-with-deps-1.8.1%2Bcu111.zip

unzip libtorch-shared-with-deps-1.8.1+cu111.zip
cd libtorch
export Torch_DIR=$(pwd)
export LD_LIBRARY_PATH=$Torch_DIR/lib:$LD_LIBRARY_PATH

Note:

  • If you want to save libtorch env variables to bashrc, you could run

    echo '# set env for libtorch' >> ~/.bashrc
echo "export Torch_DIR=${Torch_DIR}" >> ~/.bashrc
echo 'export LD_LIBRARY_PATH=$Torch_DIR/lib:$LD_LIBRARY_PATH' >> ~/.bashrc
source ~/.bashrc

Build on Linux

cd ${MMDEPLOY_DIR} # To MMDeploy root directory
mkdir -p build && cd build
cmake -DMMDEPLOY_TARGET_BACKENDS=torchscript -DTorch_DIR=${Torch_DIR} ..
make -j$(nproc) && make install

How to convert a model

SDK backend

TorchScript SDK backend may be built by passing -DMMDEPLOY_TORCHSCRIPT_SDK_BACKEND=ON to cmake.

Notice that libtorch is sensitive to C++ ABI versions. On platforms defaulted to C++11 ABI (e.g. Ubuntu 16+) one may pass -DCMAKE_CXX_FLAGS="-D_GLIBCXX_USE_CXX11_ABI=0" to cmake to use pre-C++11 ABI for building. In this case all dependencies with ABI sensitive interfaces (e.g. OpenCV) must be built with pre-C++11 ABI.

FAQs

  • Error: projects/thirdparty/libtorch/share/cmake/Caffe2/Caffe2Config.cmake:96 (message):Your installed Caffe2 version uses cuDNN but I cannot find the cuDNN libraries. Please set the proper cuDNN prefixes and / or install cuDNN.

    May export CUDNN_ROOT=/root/path/to/cudnn to resolve the build error.