xplains the use and usage of the inline assembly feature provided by GCC. There are only two prerequisites for reading this article, and that’s obviously a basic knowledge of x86 assembly language and C.
Target the parts of your applications that take the most time, by Martyn Honeyford "Improving the performance of your applications is rarely a wasted effort, but it's not always clear which functions the program is spending most of its execution time on. Learn how to pinpoint performance bottlenecks using gprof for both user-space and system calls on Linux®."
by Bill Green. using the Sobel and the Laplace methods."Edges characterize boundaries and are therefore a problem of fundamental importance in image processing"