I need to do a realtime 512 point autocorrelation for a seismic project but my poor little Parallax computer is getting swamped by all the floating point multiplies. The answer seems to be in the fast Walsh Transform. I bought some IEEE papers on the subject but they are a little deep! Does anyone have any words of encouragement? According to Wiener-Khinchin I can get the same effect by taking the fft of the data, multiplying by the complex conjugate, and taking the inverse FFT. I tried this too on Scilab but it doesnt seem to really work. Any thoughts appreciated.