added FFTW2 support

endif()

if(ENABLE_KSPACE)

  find_package(FFTW3)

  find_package(MKL)

  if(FFTW3_FOUND)

    add_definitions(-DFFT_FFTW3)

    include_directories(${FFTW3_INCLUDE_DIRS})

    list(APPEND LAMMPS_LINK_LIBS ${FFTW3_LIBRARIES})

  elseif(MKL_FOUND)

    add_definitions(-DFFT_MKL)

    include_directories(${MKL_INCLUDE_DIRS})

    list(APPEND LAMMPS_LINK_LIBS ${MKL_LIBRARIES})

  foreach(FFT FFTW3 MKL FFTW2)

    find_package(${FFT})

    if(${FFT}_FOUND)

      add_definitions(-DFFT_${FFT})

      include_directories(${${FFT}_INCLUDE_DIRS})

      list(APPEND LAMMPS_LINK_LIBS ${${FFT}_LIBRARIES})

      break()

    endif()

  endforeach()

  set(PACK_OPTIMIZATION "PACK_ARRAY" CACHE STRING "Optimization for FFT")

  set_property(CACHE LAMMPS_SIZE_LIMIT PROPERTY STRINGS PACK_ARRAY PACK_POINTER PACK_MEMCPY)

  if(NOT PACK_OPTIMIZATION STREQUAL "PACK_ARRAY")

# - Find fftw2

# Find the native FFTW2 headers and libraries.

#

#  FFTW2_INCLUDE_DIRS - where to find fftw2.h, etc.

#  FFTW2_LIBRARIES    - List of libraries when using fftw2.

#  FFTW2_FOUND        - True if fftw2 found.

#

find_path(FFTW2_INCLUDE_DIR fftw.h)

find_library(FFTW2_LIBRARY NAMES fftw)

set(FFTW2_LIBRARIES ${FFTW2_LIBRARY})

set(FFTW2_INCLUDE_DIRS ${FFTW2_INCLUDE_DIR})

include(FindPackageHandleStandardArgs)

# handle the QUIETLY and REQUIRED arguments and set FFTW2_FOUND to TRUE

# if all listed variables are TRUE

find_package_handle_standard_args(FFTW2 DEFAULT_MSG FFTW2_LIBRARY FFTW2_INCLUDE_DIR)

mark_as_advanced(FFTW2_INCLUDE_DIR FFTW2_LIBRARY )