cmake: add FFT_SINGLE option

endif()

if(ENABLE_KSPACE)

  option(FFT_SINGLE "Use single precision FFT instead of double" OFF)

  set(FFTW "FFTW3")

  if(FFT_SINGLE)

    set(FFTW "FFTW3F")

    add_definitions(-DFFT_SINGLE)

  endif()

  find_package(${FFTW} QUIET)

  if(${FFTW}_FOUND)

    set(FFT "${{FFTW}" CACHE STRING "FFT library for KSPACE package")

  else()

    set(FFT "KISSFFT" CACHE STRING "FFT library for KSPACE package")

  set_property(CACHE FFT PROPERTY STRINGS KISSFFT FFTW3 MKL)

  endif()

  set_property(CACHE FFT PROPERTY STRINGS KISSFFT ${FFTW} MKL)

  if(NOT FFT STREQUAL "KISSFFT")

    find_package(${FFT} REQUIRED)

    if(NOT FFT STREQUAL "FFTW3F")

	    add_definitions(-DFFT_FFTW)

    else()

      add_definitions(-DFFT_${FFT})

    endif()

    include_directories(${${FFT}_INCLUDE_DIRS})

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

  endif()

# - Find fftw3f

# Find the native FFTW3F headers and libraries.

#

#  FFTW3F_INCLUDE_DIRS - where to find fftw3f.h, etc.

#  FFTW3F_LIBRARIES    - List of libraries when using fftw3f.

#  FFTW3F_FOUND        - True if fftw3f found.

#

find_package(PkgConfig)

pkg_check_modules(PC_FFTW3F fftw3f)

find_path(FFTW3F_INCLUDE_DIR fftw3f.h HINTS ${PC_FFTW3F_INCLUDE_DIRS})

find_library(FFTW3F_LIBRARY NAMES fftw3f HINTS ${PC_FFTW3F_LIBRARY_DIRS})

set(FFTW3F_LIBRARIES ${FFTW3F_LIBRARY})

set(FFTW3F_INCLUDE_DIRS ${FFTW3F_INCLUDE_DIR})

include(FindPackageHandleStandardArgs)

# handle the QUIETLY and REQUIRED arguments and set FFTW3F_FOUND to TRUE

# if all listed variables are TRUE

find_package_handle_standard_args(FFTW3F DEFAULT_MSG FFTW3F_LIBRARY FFTW3F_INCLUDE_DIR)

mark_as_advanced(FFTW3F_INCLUDE_DIR FFTW3F_LIBRARY )