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

Chapter 5 Fast Fourier Transforms 571
Real-to-complex two-dimensional FFT CRC2FT/ZRC2FT
Usage VECLIB:
INTEGER*4 l1, l2, ldz, iopt, ier
COMPLEX*8 z(ldz, l2)
CALL CRC2FT(z, l1, l2, ldz, iopt, ier)
INTEGER*4 l1, l2, ldz, iopt, ier
COMPLEX*16 z(ldz, l2)
CALL ZRC2FT(z, l1, l2, ldz, iopt, ier)
VECLIB8:
INTEGER*8 l1, l2, ldz, iopt, ier
COMPLEX*8 z(ldz, l2)
CALL CRC2FT(z, l1, l2, ldz, iopt, ier)
INTEGER*8 l1, l2, ldz, iopt, ier
COMPLEX*16 z(ldz, l2)
CALL ZRC2FT(z, l1, l2, ldz, iopt, ier)
Input z Array of data to be transformed. For a forward
real-to-complex transform, only the real parts of z are
used as input. For an inverse complex-to-real
transform, only the first l1/2+1rows of z are used as
input.
l1 Number of rows of data, l1 > 0.
l2 Number of columns of data, l2 > 0.
ldz The leading dimension of array z, with ldz ≥ l1.
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. For an inverse complex-to-real transform, the
real result is stored in the real parts of z and the
imaginary parts of z are set to zero.