nvcc fatal : Unknown option 'fopenmp' using CMAKE

[adujardin]

Hi,
Using the vanilla CMakeLists to compile I have the following issue on Ubuntu 18 (default cmake 3.10.2, g++ 7.4), CUDA 10 :

nvcc fatal : Unknown option 'fopenmp'

I tried several fixes, including replacing --compiler-options by -Xcompiler as a common fix for this issue with no luck, here:

darknet/CMakeLists.txt

Line 171 in 5b8929b

set(CMAKE_CUDA_FLAGS "-gencode arch=compute_${CUDA_COMPUTE_MODEL},code=[sm_${CUDA_COMPUTE_MODEL},compute_${CUDA_COMPUTE_MODEL}] --compiler-options \"-Wall -Wno-unused-result -Wno-unknown-pragmas -Wfatal-errors -Wno-deprecated-declarations -fPIC -fopenmp -Ofast -DOPENCV -DGPU -DCUDNN \" ${CMAKE_CUDA_FLAGS}")

One solution found was to comment these lines:

darknet/CMakeLists.txt

Lines 306 to 307 in 5b8929b

	target_link_libraries(darknet PRIVATE OpenMP::OpenMP_CXX)
	target_link_libraries(darklib PRIVATE OpenMP::OpenMP_CXX)

@cenit Do you have an idea why nvcc complains about that?
Are these 2 lines necessary?

[cenit]

Hi @adujardin
let's fix this problem. First of all do you have the same symptoms using #2952? I fixed CMakeLists.txt a little bit there, I am waiting on @AlexeyAB for some feedback for merge but otherwise it should be production ready

[adujardin]

Hi @cenit
I tried your branch, however, I have the same issue.

Do you know if there's a way to check if a library have been compiled with OpenMP? I would like to check if removing these makes a difference on the final lib/exe.

darknet/CMakeLists.txt

Lines 306 to 307 in 5b8929b

	target_link_libraries(darknet PRIVATE OpenMP::OpenMP_CXX)
	target_link_libraries(darklib PRIVATE OpenMP::OpenMP_CXX)

Edit: removed other unrelated issues for clarity, see below

[adujardin]

Just in case I also tried with the docker image provided by nvidia matching my configuration to have a clean setup.

I don't have the issues mentioned above, except the nvcc fatal : Unknown option 'fopenmp'.
You can ignore those, I'll try to investigate why since I installed it using the standard way.

[cenit]

A proper fix is contained in #3371