Fast Fourier Transform code for a pruned input sequence to accompany the paper S. Holm, "FFT Pruning Applied to Time Domain Interpolation and Peak Localization", IEEE Trans. Acoust.,Speech, Sign. Proc., vol ASSP-35, pp. 1776-1778, Dec. 1987
Algorithm that takes the input array 'zr' of size N=2**m with 'kband' non-zero values starting from index 'kinit' and forward ('isign = 1') or inverse ('isign = -1') Fourier transforms it. The N output samples are found in 'zr'
Number of complex multiplications is (N/2)log(2) kband rather than (N/2)log(2) N
Written by: Sverre Holm, Informasjonskontroll a.s, Asker, NORWAY. Now at University of Oslo, Norway