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

Chapter 5 Fast Fourier Transforms 581
Real-to-complex three-dimensional FFT SRC3FT/DRC3FT
For an inverse complex-to-real transform, the real part
of Z(m
1
,m
2
,m
3
) is stored in x(2×m
1
−1,m
2
,m
3
)and the
imaginary part is stored in x(2×m
1
,m
2
,m
3
),
m
1
= 1, 2, ..., l1/2+1, m
2
= 1, 2, ..., l2,
m
3
= 1, 2, ..., l3.
l1 Number of rows of data, l1 > 0.
l2 Number of columns of data, l2 > 0.
l3 Number of planes of data, l3 > 0.
ldx The leading dimension of array x, with ldx ≥ l1+2.
mdx The middle dimension of array x, with mdx ≥ l2.
iopt Option flag:
iopt ≥ 0 Compute forward transform.
iopt < 0 Compute inverse transform.
Output x The transformed data replaces the input if ier = 0 is
returned.
For a forward real-to-complex transform, the real part
of Z(m
1
,m
2
,m
3
) is stored in x(2×m
1
−1,m
2
,m
3
)and the
imaginary part is stored in x(2×m
1
,m
2
,m
3
),
m
1
= 1, 2, ..., l1/2+1, m
2
= 1, 2, ..., l2,
m
3
= 1, 2, ..., l3.
If needed, the remaining (l1/2 − 1) × l2 × l3 complex
output values may be formed by using the
conjugate-symmetry condition.
For an inverse complex-to-real transform, the real
output point z(n
1
,n
2
,n
3
) is stored in x(n
1
,n
2
,n
3
),
n
1
= 1, 2, ..., l1, n
2
= 1, 2, ..., l2, n
3
= 1, 2, ..., l3.
ier Status response:
ier = 0 Normal return—transform successful.
ier = −1 l1 ≤ 0.
ier = −2 l2 ≤ 0.
ier
= −3 l3 ≤ 0.
ier
= −4 ldx < l1+2.
ier = −5 mdx < l2.
ier
≤−6 Probable error in ldx or mdx.