This program calculates the fast fourier transform of very long
series, as long as your far heap allows. For example, using double
precision it is posible to process 70.000 real data points. It
implements r. C. Singleton's mixed radix fast fourier algorithm.
Some features of this algorithm are: 1) the length of the series
does not have to be be necessarily a power of two, the length
may include factors of 2 and 4, and also odd factors as 3,5,7,
etc,2-) to avoid truncation errors, the sines and cosines are
generated recursively, 3-) the data and its trtransform are accessed
with huge pointers.
The source code is written in C.
(adapted from the documentation)