build lib/gpu as a library

    if(NOT BIN2C)

      message(FATAL_ERROR "Couldn't find bin2c, use -DBIN2C helping cmake to find it.")

    endif()

    include_directories(${CUDA_INCLUDE_DIRS})

    list(APPEND LAMMPS_LINK_LIBS ${CUDA_LIBRARIES} ${CUDA_CUDA_LIBRARY})

    set(GPU_PREC "SINGLE_DOUBLE" CACHE STRING "Lammps gpu precision size")

    set_property(CACHE GPU_PREC PROPERTY STRINGS SINGLE_DOUBLE SINGLE_SINGLE DOUBLE_DOUBLE)

    add_definitions(-D_${GPU_PREC})

    add_definitions(-DNV_KERNEL -DUCL_CUDADR)

    option(CUDPP_OPT "Enable CUDPP_OPT" ON)

    set(GPU_SOURCES_DIR ${LAMMPS_SOURCE_DIR}/GPU)

    set(GPU_SOURCES ${GPU_SOURCES_DIR}/gpu_extra.h)

    set_property(GLOBAL PROPERTY "GPU_SOURCES" "${GPU_SOURCES}")

    # detects styles which have GPU version

    RegisterStylesExt(${GPU_SOURCES_DIR} opt GPU_SOURCES)

    get_property(GPU_SOURCES GLOBAL PROPERTY GPU_SOURCES)

    file(GLOB GPU_LIB_SOURCES ${LAMMPS_LIB_SOURCE_DIR}/gpu/*.cpp)

    file(GLOB GPU_LIB_CU ${LAMMPS_LIB_SOURCE_DIR}/gpu/*.cu ${CMAKE_SOURCE_DIR}/gpu/*.cu)

    file(GLOB_RECURSE GPU_NOT_LIB_CU ${LAMMPS_LIB_SOURCE_DIR}/gpu/lal_pppm.cu)

    list(REMOVE_ITEM GPU_LIB_CU ${GPU_NOT_LIB_CU})

    include_directories(${GPU_SOURCES_DIR} ${LAMMPS_LIB_SOURCE_DIR}/gpu ${LAMMPS_LIB_BINARY_DIR}/gpu)

    # still missing a way to limit defines to GPU build only

    # something like cuda_compile_definitions()

    # one way is this, the other adding it to OPTIONS

    add_definitions(-D_${GPU_PREC})

    add_definitions(-DNV_KERNEL -DUCL_CUDADR)

    cuda_include_directories(${LAMMPS_LIB_SOURCE_DIR}/gpu ${LAMMPS_LIB_BINARY_DIR}/gpu)

    if(CUDPP_OPT)

      include_directories(${LAMMPS_LIB_SOURCE_DIR}/gpu/cudpp_mini)

      add_definitions(-DCUDPP_OPT)

      cuda_include_directories(${LAMMPS_LIB_SOURCE_DIR}/gpu/cudpp_mini)

      file(GLOB GPU_LIB_CUDPP_SOURCES ${LAMMPS_LIB_SOURCE_DIR}/gpu/cudpp_mini/*.cpp)

      file(GLOB GPU_LIB_CUDPP_CU ${LAMMPS_LIB_SOURCE_DIR}/gpu/cudpp_mini/*.cu)

    endif()

    cuda_compile(GPU_OBJS ${GPU_LIB_CU} ${GPU_LIB_CUDPP_CU} OPTIONS $<$<BOOL:${BUILD_SHARED_LIBS}>:-Xcompiler=-fPIC>)    

    file(MAKE_DIRECTORY ${LAMMPS_LIB_BINARY_DIR}/gpu)

    foreach(CU_OBJ ${GPU_OBJS})

      get_filename_component(CU_NAME ${CU_OBJ} NAME_WE)

        COMMAND ${BIN2C} -c -n ${CU_NAME} ${CU_OBJ} > ${LAMMPS_LIB_BINARY_DIR}/gpu/${CU_NAME}_cubin.h

        DEPENDS ${CU_OBJ} 

        COMMENT "Generating ${CU_NAME}_cubin.h")

      list(APPEND LIB_SOURCES ${LAMMPS_LIB_BINARY_DIR}/gpu/${CU_NAME}_cubin.h)

      list(APPEND GPU_LIB_SOURCES ${LAMMPS_LIB_BINARY_DIR}/gpu/${CU_NAME}_cubin.h)

      if(${CU_NAME} STREQUAL "pppm_d") #pppm_d doesn't get linked into the lib

        set(CU_FORBIDDEN_OBJ "${CU_OBJ}") 

      endif()

    endforeach()

    list(REMOVE_ITEM GPU_OBJS "${CU_FORBIDDEN_OBJ}")

    list(APPEND LIB_SOURCES ${GPU_SOURCES} ${GPU_LIB_SOURCES} ${GPU_LIB_CUDPP_SOURCES} ${GPU_OBJS})

    set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES "${LAMMPS_LIB_BINARY_DIR}/gpu/*_cubin.h")

    cuda_add_library(gpu ${GPU_LIB_SOURCES} ${GPU_LIB_CUDPP_SOURCES} ${GPU_OBJS} STATIC)

    target_include_directories(gpu PRIVATE ${LAMMPS_LIB_BINARY_DIR}/gpu)

    if(CUDPP_OPT)

      target_include_directories(gpu PRIVATE ${LAMMPS_LIB_SOURCE_DIR}/gpu/cudpp_mini)

      target_compile_definitions(gpu PRIVATE -DUSE_CUDPP)

    endif()

    list(APPEND LAMMPS_LINK_LIBS gpu)

    # GPU package

    set(GPU_SOURCES_DIR ${LAMMPS_SOURCE_DIR}/GPU)

    set(GPU_SOURCES ${GPU_SOURCES_DIR}/gpu_extra.h)

    include_directories(${GPU_SOURCES_DIR})

    set_property(GLOBAL PROPERTY "GPU_SOURCES" "${GPU_SOURCES}")

    # detects styles which have GPU version

    RegisterStylesExt(${GPU_SOURCES_DIR} opt GPU_SOURCES)

    get_property(GPU_SOURCES GLOBAL PROPERTY GPU_SOURCES)

    list(APPEND LIB_SOURCES ${GPU_SOURCES})

endif()

######################################################