cmake: add Eigen3 download for USER-SMD

endif()

if(ENABLE_USER-SMD)

  find_package(Eigen3 REQUIRED)

  option(DOWNLOAD_Eigen3 "Download Eigen3 (instead of using the system's one)" OFF)

  if(DOWNLOAD_Eigen3)

    include(ExternalProject)

    ExternalProject_Add(Eigen3_build

      URL http://bitbucket.org/eigen/eigen/get/3.3.4.tar.gz 

      URL_MD5 1a47e78efe365a97de0c022d127607c3

      CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR> -DEIGEN_TEST_NOQT=ON

        -DCMAKE_DISABLE_FIND_PACKAGE_LAPACK=ON -DCMAKE_DISABLE_FIND_PACKAGE_Cholmod=ON -DCMAKE_DISABLE_FIND_PACKAGE_Umfpack=ON -DCMAKE_DISABLE_FIND_PACKAGE_SuperLU=ON

        -DCMAKE_DISABLE_FIND_PACKAGE_PASTIX=ON -DCMAKE_DISABLE_FIND_PACKAGE_SPQR=ON -DCMAKE_DISABLE_FIND_PACKAGE_Boost=ON -DCMAKE_DISABLE_FIND_PACKAGE_CUDA=ON

        -DCMAKE_DISABLE_FIND_PACKAGE_FFTW=ON -DCMAKE_DISABLE_FIND_PACKAGE_MPFR=ON -DCMAKE_DISABLE_FIND_PACKAGE_OpenGL=ON

        )

    ExternalProject_get_property(Eigen3_build INSTALL_DIR)

    set(EIGEN3_INCLUDE_DIR ${INSTALL_DIR}/include/eigen3)

    list(APPEND LAMMPS_DEPS Eigen3_build)

  else()

    find_package(Eigen3 QUIET)

    if(NOT Eigen3_FOUND)

      message(FATAL_ERROR "Eigen3 not found, help CMake to find it by setting EIGEN3_INCLUDE_DIR, or set DOWNLOAD_Eigen3=ON to download it")

    endif()

  endif()

  include_directories(${EIGEN3_INCLUDE_DIR})

endif()