Contents
sfftcm - initialize the trigonometric weight and factor
tables or compute the one-dimensional forward Fast Fourier
Transform of a set of real data sequences stored in a two-
dimensional array.
SUBROUTINE SFFTCM(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
REAL X(LDX, *), SCALE, TRIGS(*), WORK(*)
COMPLEX Y(LDY, *)
SUBROUTINE SFFTCM_64(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER*8 IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
REAL X(LDX, *), SCALE, TRIGS(*), WORK(*)
COMPLEX Y(LDY, *)
F95 INTERFACE
SUBROUTINE FFTM(IOPT, [N1], [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS,
IFAC, WORK, [LWORK], IERR)
INTEGER*4, INTENT(IN) :: IOPT
INTEGER*4, INTENT(IN), OPTIONAL :: N1, N2, LDX, LDY, LWORK
REAL, INTENT(IN), OPTIONAL :: SCALE
REAL, INTENT(IN), DIMENSION(:,:) :: X
COMPLEX, INTENT(OUT), DIMENSION(:,:) :: Y
REAL, INTENT(INOUT), DIMENSION(:) :: TRIGS
INTEGER*4, INTENT(INOUT), DIMENSION(:) :: IFAC
REAL, INTENT(OUT), DIMENSION(:) :: WORK
INTEGER*4, 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, INTENT(IN), OPTIONAL :: SCALE
REAL, INTENT(IN), DIMENSION(:,:) :: X
COMPLEX, INTENT(OUT), DIMENSION(:,:) :: Y
REAL, INTENT(INOUT), DIMENSION(:) :: TRIGS
INTEGER(8), INTENT(INOUT), DIMENSION(:) :: IFAC
REAL, INTENT(OUT), DIMENSION(:) :: WORK
INTEGER(8), INTENT(OUT) :: IERR
C INTERFACE
#include <sunperf.h>
void sfftcm_ (int *iopt, int *n1, int *n2, float *scale,
float *x, int *ldx, complex *y, int *ldy, float
*trigs, int *ifac, float *work, int *lwork, int
*ierr);
void sfftcm_64_ (long *iopt, long *n1, long *n2, float
*scale, float *x, long *ldx, complex *y, long
*ldy, float *trigs, long *ifac, float *work, long
*lwork, long *ierr);
sfftcm initializes the trigonometric weight and factor
tables or computes the one-dimensional forward Fast Fourier
Transform of a set of real 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)
Real scalar by which transform results are scaled.
Unchanged on exit. SCALE is defaulted to 1.0 for
F95 INTERFACE.
X (input) X is a real 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 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)
Real array of length 2*N1 that contains the tri-
gonometric 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)
Real array of dimension at least N1. 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 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