Figure 7.3.2: Butterfly PE
One particular problem of the FFT is its less regular data transport.
Figure 7.3.3 shows the wiring of the butterfly PEs for N = 8. If the
PEs are configured such that the PEs with lower exponents of w come
in each stage, a configuration results with identical communication networks
between each stage. This communication network is called a perfect
since each of the pairs