FIND_PATH(EIGEN3_INCLUDE_DIR Eigen/Core /usr/include /usr/include/eigen3)
IF ( EIGEN3_INCLUDE_DIR )
    MESSAGE(STATUS "-- Looking for Eigen3 - found")
ELSE ( EIGEN3_INCLUDE_DIR )
    MESSAGE(FATAL_ERROR "-- Looking for Eigen3 - not found")
ENDIF ( EIGEN3_INCLUDE_DIR )
