CMakeLists 增加 OpenMP 的支持

find_package(OpenMP REQUIRED)
if(OpenMP_FOUND)
    message(STATUS "found openmp") 
    set(CMAKE_C_FLAGS ${CMAKE_C_FLAGS}, ${OPENMP_C_FLAGS})
    set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS}, ${OPENMP_CXX_FLAGS})
else()
    message(FATAL_ERROR "openmp not found!")
endif()

#include 

		#pragma omp parallel for
		for (int id_y = 0; id_y < num_samples_y; ++id_y) 
		{
			
		}

如果平台不支持 OpenMP，会自动降级成串行执行；