Question: What Is the Algorithm? From the shape of the slowest times or greatest flops versus N plot, you should be able to conjecture what kind of algorithm is being used for a single prime-length FFf. From the next few distinct groupings, you should be able to determine if a decomposition is being used and if so, what kind. You should be able to tell if twiddle factors are being used by checking a length which is 3 to some high power, which, of course, must use twiddle factors. From all of this, write a program that calculates the times or flops from a formula based on your idea as to how the command is implemented. Compare the results of this formula with the measured data and correct until you have fairly good agreement. What is the algorithm being used?