Contents
cfftc2 - initialize the trigonometric weight and factor
tables or compute the two-dimensional Fast Fourier Transform
(forward or inverse) of a two-dimensional complex array.
SUBROUTINE CFFTC2(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, *), Y(LDY, *)
REAL SCALE, TRIGS(*), WORK(*)
SUBROUTINE CFFTC2_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, TRIGS(*), WORK(*)
COMPLEX X(LDX, *), Y(LDY, *)
F95 INTERFACE
SUBROUTINE FFT2(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
COMPLEX, 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 FFT2_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
COMPLEX, 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 cfftc2_ (int *iopt, int *n1, int *n2, float *scale,
complex *x, int *ldx, complex *y, int *ldy, float
*trigs, int *ifac, float *work, int *lwork, int
*ierr);
void cfftc2_64_ (long *iopt, long *n1, long *n2, float
*scale, complex *x, long *ldx, complex *y, long
*ldy, float *trigs, long *ifac, float *work, long
*lwork, long *ierr);
cfftc2 initializes the trigonometric weight and factor
tables or computes the two-dimensional Fast Fourier
Transform (forward or inverse) of a two-dimensional complex
array. In computing the two-dimensional FFT,
one-dimensional FFTs are computed along the columns of the
input array. One-dimensional FFTs are then computed along
the rows of the intermediate results.
N2-1 N1-1
Y(k1,k2) = scale * SUM SUM W2*W1*X(j1,j2)
j2=0 j1=0
where
k1 ranges from 0 to N1-1 and k2 ranges from 0 to N2-1
i = sqrt(-1)
isign = 1 for inverse transform or -1 for forward transform
W1 = exp(isign*i*j1*k1*2*pi/N1)
W2 = exp(isign*i*j2*k2*2*pi/N2)
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
N1 (input)
Integer specifying length of the transform in the
first dimension. N1 is most efficient when it is
a product of small primes. N1 >= 0. Unchanged on
exit.
N2 (input)
Integer specifying length of the transform in the
second dimension. N2 is most efficient when it is
a product of small primes. 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 input data to be transformed.
LDX (input)
Leading dimension of X. LDX >= N1 Unchanged on
exit.
Y (output)
Y is a complex array of dimensions (LDY, N2) that
contains the transform results. X and Y can be
the same array starting at the same memory loca-
tion, in which case the input data 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 = LDX Else LDY >= N1 Unchanged on exit.
TRIGS (input/output)
Real array of length 2*(N1+N2) that contains 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 or IOPT
= -1. Unchanged on exit.
IFAC (input/output)
Integer array of dimension at least 2*128 that
contains the factors of N1 and N2. The factors
are computed when the routine is called with IOPT
= 0 and they are used in subsequent calls when
IOPT = 1 or IOPT = -1. Unchanged on exit.
WORK (workspace)
Real array of dimension at least
2*MAX(N1,N2)*NCPUS where NCPUS is the number of
threads used to execute the routine. 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 = N1 < 0
-3 = N2 < 0
-4 = (LDX < N1)
-5 = (LDY < N1) or (LDY not equal LDX when X and Y
are same array)
-6 = (LWORK not equal 0) and (LWORK <
2*MAX(N1,N2)*NCPUS)
-7 = memory allocation failed
fft
On exit, entire output array Y(1:LDY, 1:N2) is overwritten.