Contents
dfftzm - initialize the trigonometric weight and factor
tables or compute the one-dimensional forward Fast Fourier
Transform of a set of double precision data sequences stored
in a two-dimensional array.
SUBROUTINE DFFTZM(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
DOUBLE PRECISION X(LDX, *), SCALE, TRIGS(*), WORK(*)
DOUBLE COMPLEX Y(LDY, *)
SUBROUTINE DFFTZM_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 PRECISION X(LDX, *), SCALE, TRIGS(*), WORK(*)
DOUBLE COMPLEX Y(LDY, *)
F95 INTERFACE
SUBROUTINE FFTM(IOPT, [N1], [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS,
IFAC, WORK, [LWORK], IERR)
INTEGER, INTENT(IN) :: IOPT
INTEGER, INTENT(IN), OPTIONAL :: N1, N2, LDX, LDY, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
REAL(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 FFTM_64(IOPT, [N1], [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER(8), INTENT(IN) :: IOPT
INTEGER(8), INTENT(IN), OPTIONAL :: N1, N2, LDX, LDY, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
REAL(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 dfftzm_ (int *iopt, int *m, int *n, double *scale, dou-
ble *x, int *ldx, doublecomplex *y, int *ldy, dou-
ble *trigs, int *ifac, double *work, int *lwork,
int *ierr);
void dfftzm_64_ (long *iopt, long *m, long *n, double
*scale, double *x, long *ldx, doublecomplex *y,
long *ldy, double *trigs, long *ifac, double
*work, long *lwork, long *ierr);
dfftzm initializes the trigonometric weight and factor
tables or computes the one-dimensional forward Fast Fourier
Transform of a set of double precision 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 forward transform
W = exp(isign*i*j*k*2*pi/N1)
In real-to-complex transform of length N1, the (N1/2+1) com-
plex output 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.
IOPT (input)
Integer specifying the operation to be performed:
IOPT = 0 computes the trigonometric weight table
and factor table
IOPT = -1 computes forward 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 precision array of dimensions (LDX,
N2) that contains the sequences to be transformed
stored in its columns.
LDX (input)
Leading dimension of X. If X and Y are the same
array, LDX = 2*LDY Else LDX >= N1 Unchanged on
exit.
Y (output)
Y is a double complex array of dimensions (LDY,
N2) that contains the transform results of the
input sequences. 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. Otherwise, it is assumed that
there is no overlap between X and Y in memory.
LDY (input)
Leading dimension of Y. LDY >= N1/2 + 1 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) or (LDX not equal 2*LDY when X and
Y are same array)
-4 = (LDY < N1/2 + 1)
-6 = (LWORK not equal 0) and (LWORK < N1)
-7 = memory allocation failed
fft