from an email by Wayne Torrey [WAPHYLZ(AT)aol.com]: I happened upon your FFT page and noticed that you have a generalized radix FFT algorithm attributed to Glassman (listed as unknown). I don't know if it is of any interest to you, but I can cite a reference by him which describes the algorithm. It appeared in the IEEE Transactions on Computers in the February, 1970 issue. It was written by J. A. Glassman who is listed as working at Hughes Aircraft in Canoga Park California. The title of the paper is "A Generalization of the Fast Fourier Transform" and describes the calculation of a n-point FFT where n is not restricted to be a power of 2. He provides a Fortran listing of the algorithm as well as the mathematical development of it. I used this algorithm and a modification of the code to implement a piece of test equipment back in the early 1970's when I was working for IBM. I have never seen another paper by Glassman, but I recently came across a reference to his generalized radix algorithm which provides an alternate (and perhaps simpler) derivation. Here is the reference: W. E. Ferguson, Jr., "A simple derivation of Glassman general-n fast Fourier transform," Comput. and Math. with Appls., vol. 8, no. 6, pp. 401-411, 1982. Also, in Report AD-A083 811, NTIS, Dec. 1979. Wayne Torrey Thanks go to for Wayne Torrey for this piece of information !