'torch/torch.h' file not found in header file - c++

Question

I'm new in Linux C++ programming. I have to use libtorch (pytorch C++ version), but I kept struggling with C++ and cmake problems. These problems really make me mad, and I need some help.
Here is a simple C++ project:
.
├── build.sh
├── CMakeLists.txt
├── load_data
│   ├── CMakeLists.txt
│   ├── include
│   │   └── load_data
│   │   └── load_data.hpp
│   └── src
│   └── load_data.cpp
└── src
└── main.cpp
But I can't build it because load_data/include/load_data/load_data.hpp cannot #include <torch/torch.h>.
The build error message:
[build] /my/path/load_data/include/load_data/load_data.hpp:4:10: fatal error: 'torch/torch.h' file not found
[build] #include <torch/torch.h>
[build] ^~~~~~~~~~~~~~~
However, if I move the #include <torch/torch.h> from the header file to the corresponding source file, the error message goes away. It makes me confused.
Files' contents:
load_data/include/load_data/load_data.hpp
#pragma once
#include <torch/torch.h>
namespace load_data
{
void try_torch();
// torch::Tensor rand_tensor();
}
load_data/src/load_data.cpp
# include "load_data/load_data.hpp"
// If I remove it from load_data.hpp and use it here, the error goes away.
// #include <torch/torch.h>
namespace load_data {
void try_torch(){
torch::Tensor tensor = torch::rand({2, 3});
std::cout << tensor << std::endl;
}
}
src/main.cpp
#include <string>
#include "load_data/load_data.hpp"
int main(int argc, char **argv)
{
load_data::try_torch();
return 0;
}
CMakeLists.txt
cmake_minimum_required (VERSION 3.21)
set(CMAKE_CXX_COMPILER clang++-13)
project(ldt-cpp-experiments VERSION 1.0.0 LANGUAGES CXX)
find_package(Torch REQUIRED)
message(STATUS "Torch_FOUND: ${Torch_FOUND}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${TORCH_CXX_FLAGS}")
add_subdirectory("load_data")
set(EXECUTABLE_NAME main)
add_executable(${EXECUTABLE_NAME} src/main.cpp)
target_link_libraries(${EXECUTABLE_NAME}
PRIVATE load_data
)
set_target_properties(${EXECUTABLE_NAME} PROPERTIES
CXX_STANDARD 20
CXX_STANDARD_REQUIRED YES
)
load_data/CMakeLists.txt
cmake_minimum_required(VERSION 3.21)
project (load_data VERSION 1.0.0 LANGUAGES CXX)
find_package(Torch REQUIRED)
message(STATUS "Torch_FOUND: ${Torch_FOUND}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${TORCH_CXX_FLAGS}")
set(LIB_NAME "load_data")
add_library(${LIB_NAME}
SHARED
)
target_sources(${LIB_NAME}
PRIVATE
${PROJECT_SOURCE_DIR}/src/load_data.cpp
)
target_sources(${LIB_NAME}
PRIVATE
${PROJECT_SOURCE_DIR}/src/load_data.cpp
${PROJECT_SOURCE_DIR}/include/load_data/load_data.hpp
)
target_include_directories(${LIB_NAME}
PUBLIC
${PROJECT_SOURCE_DIR}/include
)
target_link_libraries(${LIB_NAME}
PRIVATE
${TORCH_LIBRARIES}
)
set_target_properties(${LIB_NAME} PROPERTIES
CXX_STANDARD 20
CXX_STANDARD_REQUIRED YES
)
build.sh
cmake -S . -B build