Before revision: Prior to the advent of fast computers and the 1965 rediscovery of the fast Fourier Transform, the large number of computations necessary for the discrete Fourier Transform motivated researchers to reduce the number of calculations required, resulting in the Blackman–Tukey method , which is now obsolete .
After revision: Prior to the advent of fast computers and the 1965 rediscovery of the fast Fourier Transform() and is based on the Wiener-Khinchin theorem the large number of computations necessary for the discrete Fourier Transform motivated researchers to reduce the number of calculations required, resulting in the Blackman–Tukey method , which is now obsolete .