Contents
zfftdm - initialize the trigonometric weight and factor
tables or compute the one-dimensional inverse Fast Fourier
Transform of a set of double complex data sequences stored
in a two-dimensional array.
SUBROUTINE ZFFTDM(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
DOUBLE COMPLEX X(LDX, *)
DOUBLE PRECISION SCALE, Y(LDY, *), TRIGS(*), WORK(*)
SUBROUTINE ZFFTDM_64(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER*8 IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
DOUBLE COMPLEX X(LDX, *)
DOUBLE PRECISION SCALE, Y(LDY,*), TRIGS(*), WORK(*)
F95 INTERFACE
SUBROUTINE FFTM(IOPT, N1, [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS,
IFAC, WORK, [LWORK], IERR)
INTEGER, INTENT(IN) :: IOPT, N1
INTEGER, INTENT(IN), OPTIONAL :: N2, LDX, LDY, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
COMPLEX(8), INTENT(IN), DIMENSION(:,:) :: X
REAL(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 FFTM_64(IOPT, N1, [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER(8), INTENT(IN) :: IOPT, N1
INTEGER(8), INTENT(IN), OPTIONAL :: N2, LDX, LDY, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
COMPLEX(8), INTENT(IN), DIMENSION(:,:) :: X
REAL(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 zfftdm_ (int *iopt, int *m, int *n, double *scale,
doublecomplex *x, int *ldx, double *y, int *ldy,
double *trigs, int *ifac, double *work, int
*lwork, int *ierr);
void zfftdm_64_ (long *iopt, long *m, long *n, double
*scale, doublecomplex *x, long *ldx, double *y,
long *ldy, double *trigs, long *ifac, double
*work, long *lwork, long *ierr);
zfftdm initializes the trigonometric weight and factor
tables or computes the one-dimensional inverse Fast Fourier
Transform of a set of double complex data sequences stored
in a two-dimensional array:
N1-1
Y(k,l) = scale * SUM W*X(j,l)
j=0
where
k ranges from 0 to N1-1 and l ranges from 0 to N2-1
i = sqrt(-1)
isign = 1 for inverse transform
W = exp(isign*i*j*k*2*pi/N1)
In complex-to-real transform of length N1, the (N1/2+1) com-
plex input data points stored are the positive-frequency
half of the spectrum of the Discrete Fourier Transform. The
other half can be obtained through complex conjugation and
therefore is not stored. Furthermore, due to symmetries the
imaginary of the component of X(0,0:N2-1) and X(N1/2,0:N2-1)
(if N1 is even in the latter) is assumed to be zero and is
not referenced.
IOPT (input)
Integer specifying the operation to be performed:
IOPT = 0 computes the trigonometric weight table
and factor table
IOPT = 1 computes inverse FFT
N1 (input)
Integer specifying length of the input sequences.
N1 is most efficient when it is a product of small
primes. N1 >= 0. Unchanged on exit.
N2 (input)
Integer specifying number of input sequences. N2
>= 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) X is a double complex array of dimensions (LDX,
N2) that contains the sequences to be transformed
stored in its columns in X(0:N1/2, 0:N2-1).
LDX (input)
Leading dimension of X. LDX >= (N1/2+1) Unchanged
on exit.
Y (output)
Y is a double precision array of dimensions (LDY,
N2) that contains the transform results of the
input sequences in Y(0:N1-1,0:N2-1). X and Y can
be the same array starting at the same memory
location, in which case the input sequences are
overwritten by their transform results. Other-
wise, it is assumed that there is no overlap
between X and Y in memory.
LDY (input)
Leading dimension of Y. If X and Y are the same
array, LDY = 2*LDX Else LDY >= N1 Unchanged on
exit.
TRIGS (input/output)
double precision array of length 2*N1 that con-
tains the trigonometric weights. The weights are
computed when the routine is called with IOPT = 0
and they are used in subsequent calls when IOPT =
1. Unchanged on exit.
IFAC (input/output)
Integer array of dimension at least 128 that con-
tains the factors of N1. The factors are computed
when the routine is called with IOPT = 0 and they
are used in subsequent calls when IOPT = 1.
Unchanged on exit.
WORK (workspace)
double precision array of dimension at least N1.
The user can also choose to have the routine allo-
cate 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 or 1
-2 = N1 < 0
-3 = N2 < 0
-4 = (LDX < N1/2+1)
-5 = (LDY < N1) or (LDY not equal 2*LDX when X and
Y are same array)
-6 = (LWORK not equal 0) and (LWORK < N1)
-7 = memory allocation failed
fft