if(PKG_KOKKOS)
  # TODO: this option needs to be documented when this works with a
  # regular release version of KOKKOS, and a version compatibility check
  # of external KOKKOS lib versus what the KOKKOS package needs is required.
  option(EXTERNAL_KOKKOS "Build against external kokkos library")
  if(EXTERNAL_KOKKOS)
    find_package(Kokkos REQUIRED)
    target_link_libraries(lammps PRIVATE Kokkos::kokkos)
  else()
    set(LAMMPS_LIB_KOKKOS_SRC_DIR ${LAMMPS_LIB_SOURCE_DIR}/kokkos)
    set(LAMMPS_LIB_KOKKOS_BIN_DIR ${LAMMPS_LIB_BINARY_DIR}/kokkos)
    add_subdirectory(${LAMMPS_LIB_KOKKOS_SRC_DIR} ${LAMMPS_LIB_KOKKOS_BIN_DIR})

    set(Kokkos_INCLUDE_DIRS ${LAMMPS_LIB_KOKKOS_SRC_DIR}/core/src
                            ${LAMMPS_LIB_KOKKOS_SRC_DIR}/containers/src
                            ${LAMMPS_LIB_KOKKOS_SRC_DIR}/algorithms/src
                            ${LAMMPS_LIB_KOKKOS_BIN_DIR})
    include_directories(${Kokkos_INCLUDE_DIRS})
    target_link_libraries(lammps PRIVATE kokkos)
  endif()
  add_definitions(-DLMP_KOKKOS)

  set(KOKKOS_PKG_SOURCES_DIR ${LAMMPS_SOURCE_DIR}/KOKKOS)
  set(KOKKOS_PKG_SOURCES ${KOKKOS_PKG_SOURCES_DIR}/kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/atom_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/atom_vec_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/comm_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/comm_tiled_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/min_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/min_linesearch_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/neighbor_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/neigh_list_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/neigh_bond_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/fix_nh_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/nbin_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/npair_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/npair_halffull_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/domain_kokkos.cpp
                         ${KOKKOS_PKG_SOURCES_DIR}/modify_kokkos.cpp)

  if(PKG_KSPACE)
    list(APPEND KOKKOS_PKG_SOURCES ${KOKKOS_PKG_SOURCES_DIR}/fft3d_kokkos.cpp
                                   ${KOKKOS_PKG_SOURCES_DIR}/gridcomm_kokkos.cpp
                                   ${KOKKOS_PKG_SOURCES_DIR}/remap_kokkos.cpp)
    if(KOKKOS_ENABLE_CUDA)
      if(NOT ${FFT} STREQUAL "KISS")
        add_definitions(-DFFT_CUFFT)
	target_link_libraries(lammps PRIVATE cufft)
      endif()
    endif()
  endif()

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

  # detects styles which have KOKKOS version
  RegisterStylesExt(${KOKKOS_PKG_SOURCES_DIR} kokkos KOKKOS_PKG_SOURCES)

  # register kokkos-only styles
  RegisterNBinStyle(${KOKKOS_PKG_SOURCES_DIR}/nbin_kokkos.h)
  RegisterNPairStyle(${KOKKOS_PKG_SOURCES_DIR}/npair_kokkos.h)
  RegisterNPairStyle(${KOKKOS_PKG_SOURCES_DIR}/npair_halffull_kokkos.h)

  if(PKG_USER-DPD)
    get_property(KOKKOS_PKG_SOURCES GLOBAL PROPERTY KOKKOS_PKG_SOURCES)
    list(APPEND KOKKOS_PKG_SOURCES ${KOKKOS_PKG_SOURCES_DIR}/npair_ssa_kokkos.cpp)
    RegisterNPairStyle(${KOKKOS_PKG_SOURCES_DIR}/npair_ssa_kokkos.h)
    set_property(GLOBAL PROPERTY "KOKKOS_PKG_SOURCES" "${KOKKOS_PKG_SOURCES}")
  endif()

  get_property(KOKKOS_PKG_SOURCES GLOBAL PROPERTY KOKKOS_PKG_SOURCES)

  target_sources(lammps PRIVATE ${KOKKOS_PKG_SOURCES})
  include_directories(${KOKKOS_PKG_SOURCES_DIR})
endif()