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

586 HP MLIB User’s Guide
CRCFTS/ZRCFTS Simultaneous real-to-complex one-dimensional FFT
Similarly, if the subscript that varies between data sets is the
l, incl, n, and incn must be such that no two points of any data sets occupy the
same element of z. These subprograms detect this situation and return ier = −5
if
and
where is the greatest common divisor.
Example 1 Compute the forward discrete Fourier transform of 256 data sets data of length
1024, stored as columns of the COMPLEX*8 array Z whose dimensions are
1025 by 256.
INTEGER*4 L,INCL,N,INCN,IOPT,IER
COMPLEX*8 Z(1025,256)
L = 1024
INCL = 1
N = 256
INCN = 1025
IOPT = 1
CALL CRCFTS (Z,L,INCL,N,INCN,IOPT,IER)
IF ( IER .NE. 0 ) THEN
handle error condition
END IF
Example 2 Compute the inverse discrete Fourier transform of 1024 sets of
conjugate-symmetric complex data of length 256, stored as the rows of
COMPLEX*8 array Z whose dimensions are 1025 by 256.
INTEGER*4 L,INCL,N,INCN,IOPT,IER
COMPLEX*8 Z(1025,256)
L = 256
INCL = 1025
N = 1024
INCN = 1
IOPT = -1
CALL CRCFTS (Z,L,INCL,N,INCN,IOPT,IER)
IF ( IER .NE. 0 ) THEN
handle error condition
END IF
1st subscript, use incn = 1.
2nd subscript, use incn = ldz.
3rd subscript, use incn = ldz×mdz.
incl n gcd incl incn,()×<
incn l gcd incl incn,()× ,<
gcd(.,.)