Increase required C++ version to C++20 and CUDA version to 12 about espresso HOT 3 OPEN

Compatible toolchains to build C++ and CUDA code in Ubuntu noble:

• GCC 10.5.0 with NVCC 12.0
• GCC 11.4.0 with NVCC 12.0
• GCC 12.3.0 with NVCC 12.0
• GCC 13.2.0 with NVCC 12.0
• Clang 14.0.6 with NVCC 12.0
• Clang 17.0.6 for both C++ and CUDA code

from espresso.

When using Clang as the CUDA compiler, extra steps need to be taken when running the initial CMake configuration.

CMake cannot automatically detect default architectures:

CMake Error at /usr/share/cmake-3.27/Modules/CMakeDetermineCUDACompiler.cmake:603 (message):
  Failed to detect a default CUDA architecture.

  Compiler output:

Solution: add -D CMAKE_CUDA_ARCHITECTURES="61;75" to the CMake command to specify which architectures to build for.

CMake fails to execute enable_language(CUDA):

CMake Error at /usr/share/cmake-3.27/Modules/CMakeDetermineCompilerABI.cmake:57 (try_compile):
  Failed to generate test project build system.

Solution: only Clang 17 and Clang 18 are compatible with CUDA 12. Use for example CUDACXX=clang++-17.

Here is a minimal CMake configuration with Clang:

CC=clang-17 CXX=clang++-17 CUDACXX=clang++-17 /usr/bin/cmake .. \
    -D CMAKE_CUDA_ARCHITECTURES="61;75" -D CUDAToolkit_ROOT="/usr/lib/cuda"

A compiler warning will be generated during the build:

clang++-17: warning: CUDA version 12.0 is only partially supported [-Wunknown-cuda-version]

from espresso.

For GCC 13.2.0, one has to silence a compiler error with -D CMAKE_CUDA_FLAGS=-allow-unsupported-compiler. When compiled with this flag, the main GPU algorithms in ESPResSo (P3M, DDS, LB) still work as expected.

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