Contents
cfftsm - initialize the trigonometric weight and factor
tables or compute the one-dimensional inverse Fast Fourier
Transform of a set of complex data sequences stored in a
two-dimensional array.
SUBROUTINE CFFTSM(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
COMPLEX X(LDX, *)
REAL SCALE, Y(LDY, *), TRIGS(*), WORK(*)
SUBROUTINE CFFTSM_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 SCALE, Y(LDY,*), TRIGS(*), WORK(*)
COMPLEX X(LDX, *)
F95 INTERFACE
SUBROUTINE FFTM(IOPT, N1, [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS,
IFAC, WORK, [LWORK], IERR)
INTEGER*4, INTENT(IN) :: IOPT, N1
INTEGER*4, INTENT(IN), OPTIONAL :: N2, LDX, LDY, LWORK
REAL, INTENT(IN), OPTIONAL :: SCALE
COMPLEX, INTENT(IN), DIMENSION(:,:) :: X
REAL, 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, N1
INTEGER(8), INTENT(IN), OPTIONAL :: N2, LDX, LDY, LWORK
REAL, INTENT(IN), OPTIONAL :: SCALE
COMPLEX, INTENT(IN), DIMENSION(:,:) :: X
REAL, 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 cfftsm_ (int *iopt, int *n1, int *n2, float *scale,
complex *x, int *ldx, float *y, int *ldy, float
*trigs, int *ifac, float *work, int *lwork, int
*ierr);
void cfftsm_64_ (long *iopt, long *n1, long *n2, float
*scale, complex *x, long *ldx, float *y, long
*ldy, float *trigs, long *ifac, float *work, long
*lwork, long *ierr);
cfftsm initializes the trigonometric weight and factor
tables or computes the one-dimensional inverse Fast Fourier
Transform of a set of 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)
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 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 real 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. Otherwise, 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)
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 < N1/2+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