FAST ALGORITHMS FOR THE CONJUGATE PERIODIC FUNCTION

Two fast algorithms for the approximate computation of the conjugate periodic function are described. They are based on the fast Fourier transform and enable us to reduce the expenses to O (N log N) operations compared with O (N2) operations for Wittich's classical method. The second algorithm, for which an ALGOL 60 procedure is listed, allows to evaluate the conjugate function on the even (or odd) numbered lattice points separately. (This feature is important for some applications.) © 1979 Springer-Verlag.