Compiling example-app with CMake and Visual Studio on Windows

C++
1

Hi,

I’m trying to compile the example-app from the libtorch tutorial using Visual Studio 16 (2019).

The CMakeLists.txt file is the following:

cmake_minimum_required(VERSION 3.0 FATAL_ERROR)
project(example-app)

set(CMAKE_PREFIX_PATH "C:\\Users\\caill\\libtorch\\")

find_package(Torch REQUIRED)

add_executable(example-app example-app.cpp)
target_link_libraries(example-app "${TORCH_LIBRARIES}")
set_property(TARGET example-app PROPERTY CXX_STANDARD 11)

# The following code block is suggested to be used on Windows.
# According to https://github.com/pytorch/pytorch/issues/25457,
# the DLLs need to be copied to avoid memory errors.
if (MSVC)
  file(GLOB TORCH_DLLS "${TORCH_INSTALL_PREFIX}/lib/*.dll")
  add_custom_command(TARGET example-app
                     POST_BUILD
                     COMMAND ${CMAKE_COMMAND} -E copy_if_different
                     ${TORCH_DLLS}
                     $<TARGET_FILE_DIR:example-app>)
endif (MSVC)

When building the example, I get the following error:

C:\Users\caill\source\Repos\caillonantoine\example-app\ninja : error : 'torch-NOTFOUND', needed by 'example-app.exe', missing and no known rule to make it

I’ve been trying to find a solution to this problem online, without success. Do you by any chance know how to fix this problem? Thanks!

2

Could you please clean the cache and build the project again?

3

Hi,
I don’t know a nice way how to solve this problem, but here is a dirty solution (and it works!).

Find file ‘biuld.ninja’ . For VS2019 it’s in ‘[your_project_dir]\out\build\x64-Release’ directory.
For VS2017 I’ve found it in ‘[your_win_home_dir]\CMakeBuilds\4483b75d-3038-b138-ad88-323c5cdc1522\build\x64-Release’ directory (or Debug if you trying it).

Then you have manually replace in this text file ‘torch-NOTFOUND’ string to full path to your torch.lib (like ‘C$:\libtorch\lib\torch.lib’ (don’t ask me what ‘$’ mean after C, I don’t know. It all experimental, but it work for me.)
Save ‘build.ninja’ file and now you can build and run your project.

Wonderful, isn’t it?

4

i so had this problem and solved it . delete catch and clean all in visual studio and delete cmake_minimum_required(VERSION 3.0 FATAL_ERROR) from CMakeLists.txt. and then generate catch and build project , then works as well.

5

I slove it,
you can see libtorch-demo/example-app at main · carlsummer/libtorch-demo · GitHub,
set(CMAKE_BUILD_TYPE “Release”)

-DCMAKE_PREFIX_PATH=path\to\opencv\build\x64\vc14\lib;path\to\libtorch -DCMAKE_BUILD_TYPE=Release -G"Visual Studio 14 Win64"