zfftz(3P) Sun Performance Library zfftz(3P)NAMEzfftz - initialize the trigonometric weight and factor tables or com‐
pute the Fast Fourier transform (forward or inverse) of a double com‐
plex sequence.
SYNOPSIS
SUBROUTINE ZFFTZ(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N, IFAC(*), LWORK, IERR
DOUBLE COMPLEX X(*), Y(*)
DOUBLE PRECISION SCALE, TRIGS(*), WORK(*)
SUBROUTINE ZFFTZ_64(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER*8 IOPT, N, IFAC(*), LWORK, IERR
DOUBLE PRECISION SCALE, TRIGS(*), WORK(*)
DOUBLE COMPLEX X(*), Y(*)
F95 INTERFACE
SUBROUTINE FFT(IOPT, [N], [SCALE], X, Y, TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER, INTENT(IN) :: IOPT
INTEGER, INTENT(IN), OPTIONAL :: N, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
COMPLEX(8), INTENT(IN), DIMENSION(:) :: X
COMPLEX(8), INTENT(OUT), DIMENSION(:) :: Y
REAL(8), INTENT(INOUT), DIMENSION(:) :: TRIGS
INTEGER, INTENT(INOUT), DIMENSION(:) :: IFAC
REAL(8), INTENT(OUT), DIMENSION(:) :: WORK
INTEGER, INTENT(OUT) :: IERR
SUBROUTINE FFT_64(IOPT, [N], [SCALE], X, Y, TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER(8), INTENT(IN) :: IOPT
INTEGER(8), INTENT(IN), OPTIONAL :: N, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
COMPLEX(8), INTENT(IN), DIMENSION(:) :: X
COMPLEX(8), INTENT(OUT), DIMENSION(:) :: Y
REAL(8), INTENT(INOUT), DIMENSION(:) :: TRIGS
INTEGER(8), INTENT(INOUT), DIMENSION(:) :: IFAC
REAL(8), INTENT(OUT), DIMENSION(:) :: WORK
INTEGER(8), INTENT(OUT) :: IERR
C INTERFACE
#include <sunperf.h>
void zfftz_ (int *iopt, int *n, double *scale, doublecomplex *x, dou‐
blecomplex *y, double *trigs, int *ifac, double *work, int
*lwork, int *ierr);
void zfftz_64_ (long *iopt, long *n, double *scale, doublecomplex *x,
doublecomplex *y, double *trigs, long *ifac, double *work,
long *lwork, long *ierr);
PURPOSEzfftz initializes the trigonometric weight and factor tables or com‐
putes the Fast Fourier transform (forward or inverse) of a double com‐
plex sequence as follows:
N-1
Y(k) = scale * SUM W*X(j)
j=0
where
k ranges from 0 to N-1
i = sqrt(-1)
isign = 1 for inverse transform or -1 for forward transform
W = exp(isign*i*j*k*2*pi/N)
ARGUMENTS
IOPT (input)
Integer specifying the operation to be performed:
IOPT = 0 computes the trigonometric weight table and factor
table
IOPT = -1 computes forward FFT
IOPT = +1 computes inverse FFT
N (input)
Integer specifying length of the input sequence X. N is most
efficient when it is a product of small primes. N >= 0.
Unchanged on exit.
SCALE (input)
Double precision scalar by which transform results are
scaled. Unchanged on exit. SCALE is defaulted to 1.0D0 for
F95 INTERFACE.
X (input) On entry, X is a double complex array of dimension at least N
that contains the sequence to be transformed.
Y (output)
Double complex array of dimension at least N that contains
the transform results. X and Y may be the same array start‐
ing at the same memory location. Otherwise, it is assumed
that there is no overlap between X and Y in memory.
TRIGS (input/output)
Double precision array of length 2*N that contains the
trigonometric weights. The weights are computed when the
routine is called with IOPT = 0 and they are used in subse‐
quent calls when IOPT = 1 or IOPT = -1. Unchanged on exit.
IFAC (input/output)
Integer array of dimension at least 128 that contains the
factors of N. The factors are computed when the routine is
called with IOPT = 0 and they are used in subsequent calls
where IOPT = 1 or IOPT = -1. Unchanged on exit.
WORK (workspace)
Double precision array of dimension at least 2*N. The user
can also choose to have the routine allocate its own
workspace (see LWORK).
LWORK (input)
Integer specifying workspace size. If LWORK = 0, the routine
will allocate its own workspace.
IERR (output)
On exit, integer IERR has one of the following values:
0 = normal return
-1 = IOPT is not 0, 1 or -1
-2 = N < 0
-3 = (LWORK is not 0) and (LWORK is less than 2*N)
-4 = memory allocation for workspace failed
SEE ALSO
fft
6 Mar 2009 zfftz(3P)
