Hi Zheng Da, > Can anyone tell me what is the possible reason that can cause time difference? To understand the differences, look at the assembly dumps of the routine from the GCC compiler and the Intel compiler. Make sure you are using the right GCC machine flags -mcpu= -mtune= -march= for your platform. (Since you did not provide your command lines for GCC and Intel compilers, I can only offer that as a general suggestion.) HTH, --Eljay
