Add HIP support for the unit tests

[HanatoK]

This is only a draft PR at present. I haven't figured out how to use libhipcxx for cuda::std::array.

Update:

I have implemented colvars_gpu::array1d to avoid the use of libhipcxx. The unit tests can now be run on HIP. You can build the run_colvars_test_cuda on HIP with the following commands:

cd tests/functional_gpu
mkdir build
cd build
cmake ../ -DGPU_TYPE=HIP -DCMAKE_CXX_COMPILER:PATH=/opt/rocm/bin/amdclang++ -DCMAKE_PREFIX_PATH=/opt/rocm -DCMAKE_BUILD_TYPE=Release

and then run make and make test. The test passed on my laptop with Radeon 610M and also Frontier with MI250X (requires `-DCMAKE_HIP_ARCHITECTURES="gfx90a").

[jhenin]

This is sensitive to the toolchain version (of course). With ROCm 6.4.3 I get "use of undeclared identifier '__syncwarp'", but with ROCm 7.1.1 I get into a kind dependency hell on the machine I'm trying (it loads the wrong compiler). Not an issue with the PR itself, but that explains why I couldn't finish the test just yet.

[jhenin]

This is not working for me when cmake is run from within tests/functional_gpu/build - it's missing one level to go back to the Colvars root. I realized the same issue exists in namd/cudaglobalmaster/CMakeLists.txt. Unless I am missing something...

[HanatoK]

I am not what the best way to detect the Colvars source directory is. Could you specify -DCOLVARS_SOURCE_DIR= explicitly?

[jhenin]

I can do that but I am wondering if this default path is the correct one. Does the default work for you?

[HanatoK]

It works for me. If I understand correctly, "CMAKE_CURRENT_SOURCE_DIR" should point to the directory containing the "CMakeLists.txt" being processed.

[HanatoK]

This is sensitive to the toolchain version (of course). With ROCm 6.4.3 I get "use of undeclared identifier '__syncwarp'", but with ROCm 7.1.1 I get into a kind dependency hell on the machine I'm trying (it loads the wrong compiler). Not an issue with the PR itself, but that explains why I couldn't finish the test just yet.

The code should be OK with ROCm 7.2.0 and 7.2.2.

[HanatoK]

This is sensitive to the toolchain version (of course). With ROCm 6.4.3 I get "use of undeclared identifier '__syncwarp'", but with ROCm 7.1.1 I get into a kind dependency hell on the machine I'm trying (it loads the wrong compiler). Not an issue with the PR itself, but that explains why I couldn't finish the test just yet.

I have tried to make the code compatible with ROCm 6.4.2 in the two latest commits.