Optimize option when creating class library for 67 percent less calculation time

CMakeLists.txt

@@ -17,7 +17,7 @@ CMAKE_MINIMUM_REQUIRED(VERSION 2.8 FATAL_ERROR)
 INCLUDE(CheckCXXCompilerFlag)
 CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
 IF(COMPILER_SUPPORTS_CXX11)
-  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -O3")
 ELSE()
   MESSAGE(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
 ENDIF()