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I have Miniconda3 on a Linux system (Ubuntu 22.04). The environment has Python 3.10 as well as a functioning (in Python) installation of PyTorch (installed following official instructions).

I would like to setup a CMake project that uses PyTorch C++ API. The reason is not important and also I am aware that it’s beta (the official documentation states that), so instability and major changes are not excluded.

Currently I have this very minimal CMakeLists.txt:

cmake_minimum_required(VERSION 3.19) # or whatever version you use
project(PyTorch_Cpp_HelloWorld CXX)

set(PYTORCH_ROOT "/home/$ENV{USER}/miniconda/envs/ML/lib/python3.10/site-packages/torch")
list(APPEND CMAKE_PREFIX_PATH "${PYTORCH_ROOT}/share/cmake/Torch/")
find_package(Torch REQUIRED CONFIG)

...
# Add executable
# Link against PyTorch library

When I try to configure the project I’m getting error:

CMake Error at CMakeLists.txt:21 (message): message called with
incorrect number of arguments

— Could NOT find Protobuf (missing: Protobuf_LIBRARIES Protobuf_INCLUDE_DIR)
— Found Threads: TRUE CMake Warning at /home/USER/miniconda/envs/ML/lib/python3.10/site-packages/torch/share/cmake/Caffe2/public/protobuf.cmake:88
(message): Protobuf cannot be found. Depending on whether you are
building Caffe2 or a Caffe2 dependent library, the next warning /
error will give you more info. Call Stack (most recent call first):
/home/USER/miniconda/envs/ML/lib/python3.10/site-packages/torch/share/cmake/Caffe2/Caffe2Config.cmake:56
(include)
/home/USER/miniconda/envs/ML/lib/python3.10/site-packages/torch/share/cmake/Torch/TorchConfig.cmake:68
(find_package) CMakeLists.txt:23 (find_package)

CMake Error at
/home/USER/miniconda/envs/ML/lib/python3.10/site-packages/torch/share/cmake/Caffe2/Caffe2Config.cmake:58
(message): Your installed Caffe2 version uses protobuf but the
protobuf library cannot be found. Did you accidentally remove it,
or have you set the right CMAKE_PREFIX_PATH? If you do not have
protobuf, you will need to install protobuf and set the library path
accordingly. Call Stack (most recent call first):
/home/USER/miniconda/envs/ML/lib/python3.10/site-packages/torch/share/cmake/Torch/TorchConfig.cmake:68
(find_package) CMakeLists.txt:23 (find_package)

I installed libprotobuf (again via conda) but, while I can find the library files, I can’t find any *ProtobufConfig.cmake or anything remotely related to protobuf and its CMake setup.

Before I go fight against wind mills I would like to ask here what the proper setup would be. I am guessing building from source is always an option, however this will pose a huge overhead on people, who I collaborate with.

2

Answers


  1. As an alternative to using conda, I would suggest to just grab the pre-built library using the link https://download.pytorch.org/libtorch/nightly/cpu/libtorch-shared-with-deps-latest.zip Unzipping that will give you a folder libtorch which you can put next to your CMakeLists.txt. With that, all you need to have in your cmake (see here) would be something like this:

    project(example-app)
    
    find_package(Torch REQUIRED)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${TORCH_CXX_FLAGS}")
    
    add_executable(example-app example-app.cpp)
    target_link_libraries(example-app "${TORCH_LIBRARIES}")
    set_property(TARGET example-app PROPERTY CXX_STANDARD 14)
    
    list(APPEND CMAKE_PREFIX_PATH "libtorch")
    
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  2. Using this conda env:

    name: pytorch_latest
    channels:
      - pytorch
      - conda-forge
      - defaults
    dependencies:
      - pytorch=1.11.0
      - torchvision
      - torchaudio
      - cpuonly
    
    

    I copied the small example from here and got it to run. The key was to set the correct library directories (both torch in site-packages, but also the lib folder of the environment). The cmake file is written so that the folders are automatically found :

    example-app.cpp

    #include <torch/torch.h>
    #include <iostream>
    
    int main() {
      torch::Tensor tensor = torch::rand({2, 3});
      std::cout << tensor << std::endl;
    }
    

    CMakeLists.txt:

    cmake_minimum_required(VERSION 3.0 FATAL_ERROR)
    project(example-app)
    
    #Add the torch library directory
    list(APPEND CMAKE_PREFIX_PATH "$ENV{CONDA_PREFIX}/lib/python3.10/site-packages/torch")
    
    #This is needed to be able to find the mkl and other dependent libraries
    link_directories("$ENV{CONDA_PREFIX}/lib")
    set(ENV{MKLROOT} "$ENV{CONDA_PREFIX}/lib")
    find_package(Torch REQUIRED)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${TORCH_CXX_FLAGS}")
    
    add_executable(example-app example-app.cpp)
    
    #We need to add pthread and omp manually here
    target_link_libraries(example-app "${TORCH_LIBRARIES}" pthread omp)
    
    set_property(TARGET example-app PROPERTY CXX_STANDARD 14)
    

    Exact environment (in case there are problems with reproducibility):

    name: pytorch_latest
    channels:
      - pytorch
      - conda-forge
      - defaults
    dependencies:
      - _libgcc_mutex=0.1=conda_forge
      - _openmp_mutex=4.5=2_kmp_llvm
      - blas=2.115=mkl
      - blas-devel=3.9.0=15_linux64_mkl
      - brotlipy=0.7.0=py310h5764c6d_1004
      - bzip2=1.0.8=h7f98852_4
      - ca-certificates=2022.5.18.1=ha878542_0
      - certifi=2022.5.18.1=py310hff52083_0
      - cffi=1.15.0=py310h0fdd8cc_0
      - charset-normalizer=2.0.12=pyhd8ed1ab_0
      - cpuonly=2.0=0
      - cryptography=37.0.1=py310h9ce1e76_0
      - ffmpeg=4.3=hf484d3e_0
      - freetype=2.10.4=h0708190_1
      - giflib=5.2.1=h36c2ea0_2
      - gmp=6.2.1=h58526e2_0
      - gnutls=3.6.13=h85f3911_1
      - idna=3.3=pyhd8ed1ab_0
      - jpeg=9e=h166bdaf_1
      - lame=3.100=h7f98852_1001
      - lcms2=2.12=hddcbb42_0
      - ld_impl_linux-64=2.36.1=hea4e1c9_2
      - lerc=3.0=h9c3ff4c_0
      - libblas=3.9.0=15_linux64_mkl
      - libcblas=3.9.0=15_linux64_mkl
      - libdeflate=1.10=h7f98852_0
      - libffi=3.4.2=h7f98852_5
      - libgcc-ng=12.1.0=h8d9b700_16
      - libgfortran-ng=12.1.0=h69a702a_16
      - libgfortran5=12.1.0=hdcd56e2_16
      - libiconv=1.17=h166bdaf_0
      - liblapack=3.9.0=15_linux64_mkl
      - liblapacke=3.9.0=15_linux64_mkl
      - libnsl=2.0.0=h7f98852_0
      - libpng=1.6.37=h21135ba_2
      - libstdcxx-ng=12.1.0=ha89aaad_16
      - libtiff=4.4.0=h0fcbabc_0
      - libuuid=2.32.1=h7f98852_1000
      - libuv=1.43.0=h7f98852_0
      - libwebp=1.2.2=h3452ae3_0
      - libwebp-base=1.2.2=h7f98852_1
      - libxcb=1.13=h7f98852_1004
      - libzlib=1.2.12=h166bdaf_0
      - llvm-openmp=14.0.4=he0ac6c6_0
      - lz4-c=1.9.3=h9c3ff4c_1
      - mkl=2022.1.0=h84fe81f_915
      - mkl-devel=2022.1.0=ha770c72_916
      - mkl-include=2022.1.0=h84fe81f_915
      - ncurses=6.3=h27087fc_1
      - nettle=3.6=he412f7d_0
      - numpy=1.22.4=py310h4ef5377_0
      - openh264=2.1.1=h780b84a_0
      - openjpeg=2.4.0=hb52868f_1
      - openssl=3.0.3=h166bdaf_0
      - pillow=9.1.1=py310he619898_1
      - pip=22.1.2=pyhd8ed1ab_0
      - pthread-stubs=0.4=h36c2ea0_1001
      - pycparser=2.21=pyhd8ed1ab_0
      - pyopenssl=22.0.0=pyhd8ed1ab_0
      - pysocks=1.7.1=py310hff52083_5
      - python=3.10.4=h2660328_0_cpython
      - python_abi=3.10=2_cp310
      - pytorch=1.11.0=py3.10_cpu_0
      - pytorch-mutex=1.0=cpu
      - readline=8.1=h46c0cb4_0
      - requests=2.27.1=pyhd8ed1ab_0
      - setuptools=62.3.2=py310hff52083_0
      - sqlite=3.38.5=h4ff8645_0
      - tbb=2021.5.0=h924138e_1
      - tk=8.6.12=h27826a3_0
      - torchaudio=0.11.0=py310_cpu
      - torchvision=0.12.0=py310_cpu
      - typing_extensions=4.2.0=pyha770c72_1
      - tzdata=2022a=h191b570_0
      - urllib3=1.26.9=pyhd8ed1ab_0
      - wheel=0.37.1=pyhd8ed1ab_0
      - xorg-libxau=1.0.9=h7f98852_0
      - xorg-libxdmcp=1.1.3=h7f98852_0
      - xz=5.2.5=h516909a_1
      - zlib=1.2.12=h166bdaf_0
      - zstd=1.5.2=h8a70e8d_1
    
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