HP MLIB User's Guide Vol. 2 7th Ed.

Chapter 5 Fast Fourier Transforms 557
Simultaneous one-dimensional FFT CFFTS/ZFFTS
VECLIB8:
INTEGER*8 l, incl, n, incn, iopt, ier
COMPLEX*8 z(lenz)
CALL CFFTS(z, l, incl, n, incn, iopt, ier)
INTEGER*8 l, incl, n, incn, iopt, ier
COMPLEX*16 z(lenz)
CALL ZFFTS(z, l, incl, n, incn, iopt, ier)
Input z Array containing n data sets, each consisting of l data
points, to be transformed. Typically, z will be a two- or
three-dimensional array with each set of data being a
one-dimensional array section. Refer to “Notes” for
suggested usages. Treating z as a one-dimensional
array results in
The i-th data point of the j-th data set, 1 ≤ i ≤ l,
1 ≤ j ≤ n, is stored in
z((i−1)×incl + (j−1)×incn + 1).
l Number of data points in each data set, l > 0.
incl Storage increment between successive elements of the
same data set, incl > 0. Use incl = 1 if each data set is
stored contiguously in array z.
n The number of data sets, n > 0.
incn Storage increment between corresponding data points
of successive data sets, incn > 0.
iopt Option flag:
iopt ≥ 0 Compute forward transform.
iopt < 0 Compute inverse transform.
Output z The transformed data replaces the input if ier = 0 is
returned. Unchanged if ier < 0.
ier Status response:
ier = 0 Normal return—transform successful.
ier = −1 l ≤ 0.
lenz l 1–()incl× n 1–()+ incn× 1.+=