mhubii/A guide to install and use the PyTorch C++ API with Anaconda.md

## A guide to install and use the PyTorch C++ API with Anaconda.md

      
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              A guide to install and use the PyTorch C++ API with Anaconda.md
            
          
    PyTorch C++ API Ubuntu Installation Guide

The best way to get a clean installation of PyTorch, is to install the pre-compiled binaries from the Anaconda distribution. Therefore, we need to setup Anaconda first.
Step 1: Install Anaconda


Go to the download section and download your desired Anaconda version for Linux


Run the downloaded shell script and follow the install instruction, do

cd ~/Downloads
sh Anaconda3-2021.11-Linux-x86_64.sh # actual name depends on your download
Step 2: Setup an Environment


To keep things clean, now setup an environment for Anaconda, do

conda create --name py39_torch python=3.9 # you can choose the name of the environment and the python version

Activate the environment

conda activate py39_torch
Step 3: Install PyTorch

There are two different ways on how to proceed.
Install pre-compiled Binaries


Go to pytorch.org and choose your desired settings like so


Run the proposed command, and make sure your environment is activated

conda install pytorch-cpu torchvision-cpu -c pytorch
Install from Source

Sometimes you want to compile from source, due to specific dependencies for example. You can look up what to do here. The main steps are

Get dependencies

conda install numpy ninja pyyaml mkl mkl-include setuptools cmake cffi typing

In case you want to use CUDA on a GPU, otherwise you can skip

# Add LAPACK support for the GPU if needed
conda install -c pytorch magma-cuda90 # or [magma-cuda92 | magma-cuda100 ] depending on your cuda version

Clone PyTorch from GitHub

git clone --recursive https://github.com/pytorch/pytorch
cd pytorch

Install PyTorch, make sure your environment is activated

export CMAKE_PREFIX_PATH=${CONDA_PREFIX:-"$(dirname $(which conda))/../"}
python setup.py install
Step 4: Link against libtorch.so

Great you came this far, now lets see if everything worked well. Here is a minimal example, on how to link against the C++ API of Pytorch.

Build the example, the path depends on your installation. If you followed the previous steps, it should be

mkdir build
cd build
cmake -DCMAKE_PREFIX_PATH="${HOME}/anaconda3/envs/py39_torch/lib/python3.9/site-packages/torch" ..
make

Run the example

./main
Thats it! Hope it helped you.

  
## CMakeLists.txt
cmake_minimum_required(VERSION 3.10 FATAL_ERROR)
project(example)

find_package(Torch REQUIRED)

add_executable(main main.cpp)
target_link_libraries(main ${TORCH_LIBRARIES})
set_property(TARGET main PROPERTY CXX_STANDARD 14)

## main.cpp
#include <torch/torch.h>

int main()
{
    torch::Tensor tensor = torch::zeros({2, 2});
    std::cout << tensor << std::endl;

    return 0;
}
	cmake_minimum_required(VERSION 3.10 FATAL_ERROR)
	project(example)

	find_package(Torch REQUIRED)

	add_executable(main main.cpp)
	target_link_libraries(main ${TORCH_LIBRARIES})
	set_property(TARGET main PROPERTY CXX_STANDARD 14)
	#include <torch/torch.h>

	int main()
	{
	torch::Tensor tensor = torch::zeros({2, 2});
	std::cout << tensor << std::endl;

	return 0;
	}