Easiest way to test for existence of cuda-capable GPU from cmake?

Question

We have some nightly build machines that have the cuda libraries installed, but which do not have a cuda-capable GPU installed. These machines are capable of building cuda-

Answer 1

One useful approach is to run programs that CUDA has installed, such as nvidia-smi, to see what they return.

        find_program(_nvidia_smi "nvidia-smi")
        if (_nvidia_smi)
            set(DETECT_GPU_COUNT_NVIDIA_SMI 0)
            # execute nvidia-smi -L to get a short list of GPUs available
            exec_program(${_nvidia_smi_path} ARGS -L
                OUTPUT_VARIABLE _nvidia_smi_out
                RETURN_VALUE    _nvidia_smi_ret)
            # process the stdout of nvidia-smi
            if (_nvidia_smi_ret EQUAL 0)
                # convert string with newlines to list of strings
                string(REGEX REPLACE "\n" ";" _nvidia_smi_out "${_nvidia_smi_out}")
                foreach(_line ${_nvidia_smi_out})
                    if (_line MATCHES "^GPU [0-9]+:")
                        math(EXPR DETECT_GPU_COUNT_NVIDIA_SMI "${DETECT_GPU_COUNT_NVIDIA_SMI}+1")
                        # the UUID is not very useful for the user, remove it
                        string(REGEX REPLACE " \\(UUID:.*\\)" "" _gpu_info "${_line}")
                        if (NOT _gpu_info STREQUAL "")
                            list(APPEND DETECT_GPU_INFO "${_gpu_info}")
                        endif()
                    endif()
                endforeach()

                check_num_gpu_info(${DETECT_GPU_COUNT_NVIDIA_SMI} DETECT_GPU_INFO)
                set(DETECT_GPU_COUNT ${DETECT_GPU_COUNT_NVIDIA_SMI})
            endif()
        endif()

One might also query linux /proc or lspci. See fully-worked CMake example at https://github.com/gromacs/gromacs/blob/master/cmake/gmxDetectGpu.cmake