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

574 HP MLIB User’s Guide
SRC2FT/DRC2FT Real-to-complex two-dimensional FFT
For best performance, these subprograms require that l
1
and l
2
be products of
powers of 2, 3, and 5, that is, of the form
where p
k
, q
k
, r
k
≥ 0, k = 1, 2, and where either l
1
=1 or l
1
is even.
Usage VECLIB:
INTEGER*4 l1, l2, ldx, iopt, ier
REAL*4 x(ldx, l2)
CALL SRC2FT(x, l1, l2, ldx, iopt, ier)
INTEGER*4 l1, l2, ldx, iopt, ier
REAL*8 x(ldx, l2)
CALL DRC2FT(x, l1, l2, ldx, iopt, ier)
VECLIB8:
INTEGER*8 l1, l2, ldx, iopt, ier
REAL*4 x(ldx, l2)
CALL SRC2FT(x, l1, l2, ldx, iopt, ier)
INTEGER*8 l1, l2, ldx, iopt, ier
REAL*8 x(ldx, l2)
CALL DRC2FT(x, l1, l2, ldx, iopt, ier)
Input x Array of data to be transformed.
For a forward real-to-complex transform, the real data
point z(n
1
,n
2
) is stored in x(n
1
,n
2
), n
1
= 1, 2, ..., l1,
n
2
= 1, 2, ..., l2.
For an inverse complex-to-real transform, the real part
of Z(m
1
,m
2
) is stored in x(2×m
1
−1,m
2
)and the
imaginary part is stored in x(2×m
1
,m
2
),
m
1
= 1, 2, ..., l1/2+1, m
2
= 1, 2, ..., l2.
l1 Number of rows of data, l1 > 0.
l2 Number of columns of data, l2 > 0.
ldx The leading dimension of array x, with ldx ≥ l1+2.
iopt Option flag:
iopt ≥ 0 Compute forward transform.
iopt < 0 Compute inverse transform.
l
k
2
p
k
3
q
k
5
r
k
,=