Polish code

cmake/external/xxhash.cmake

@@ -9,8 +9,6 @@ ExternalProject_Add(
     extern_xxhash
     ${EXTERNAL_PROJECT_LOG_ARGS}
     GIT_REPOSITORY  "https://github.com/Cyan4973/xxHash"
-    # eigen on cuda9.1 missing header of math_funtions.hpp
-    # https://stackoverflow.com/questions/43113508/math-functions-hpp-not-found-when-using-cuda-with-eigen
     GIT_TAG         "v0.6.5"
     PREFIX          ${XXHASH_SOURCE_DIR}
     DOWNLOAD_NAME   "xxhash"
@@ -29,15 +27,6 @@ INCLUDE_DIRECTORIES(${XXHASH_INCLUDE_DIR})
 
 add_library(xxhash STATIC IMPORTED GLOBAL)
 set_property(TARGET xxhash PROPERTY IMPORTED_LOCATION ${XXHASH_LIBRARIES})
-#if (${CMAKE_VERSION} VERSION_LESS "3.3.0")
-#    set(dummyfile ${CMAKE_CURRENT_BINARY_DIR}/lib_xxhash_dummy.c)
-#    file(WRITE ${dummyfile} "const char * dummy_any = \"${dummyfile}\";")
-#    add_library(lib_xxhash STATIC ${dummyfile})
-#else()
-#    add_library(lib_xxhash INTERFACE)
-#endif()
 include_directories(${XXHASH_INCLUDE_DIR})
 add_dependencies(xxhash extern_xxhash)
-#LIST(APPEND external_project_dependencies xxhash)
-#link_libraries(${XXHASH_LIBRARIES})