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

588 HP MLIB User’s Guide
SRCFTS/DRCFTS Simultaneous real-to-complex one-dimensional FFT
These subprograms perform forward real-to-complex or inverse complex-to-real
transform operations simultaneously on a number of data sets. For best
performance, they require that the length l of the data sets be a product of
powers of 2, 3, and 5, that is, of the form
where p, q, r ≥ 0, and where either l = 1 or l is even.
Usage VECLIB:
INTEGER*4 l, incl, n, incn, iopt, ier
REAL*4 x(lenx)
CALL SRCFTS(x, l, incl, n, incn, iopt, ier)
INTEGER*4 l, incl, n, incn, iopt, ier
REAL*8 x(lenx)
CALL DRCFTS(x, l, incl, n, incn, iopt, ier)
VECLIB8:
INTEGER*8 l, incl, n, incn, iopt, ier
REAL*4 x(lenx)
CALL SRCFTS(x, l, incl, n, incn, iopt, ier)
INTEGER*8 l, incl, n, incn, iopt, ier
REAL*8 x(lenx)
CALL DRCFTS(x, l, incl, n, incn, iopt, ier)
Input x Array containing n one-dimensional data sets, each
consisting of l real data points or the first l/2+1 complex
data points of a conjugate-symmetric complex data set
of length l, to be transformed. Typically, x is a two- or
three-dimensional array with each set of data being a
one-dimensional array section. Refer to “Notes” for
suggested usages.
Treating x as a one-dimensional array results in
For a forward real-to-complex transform, the i-th real
data point of the j-th data set, 1 ≤ i ≤ l, 1 ≤ j ≤ n, is
stored in
l 2
p
3
q
5
r
,=
lenx l 1+()incl× n 1–()incn 1.+×+=
x i 1–()incl× j 1–()+ incn× 1+().