Contents
zfftz2 - initialize the trigonometric weight and factor
tables or compute the two-dimensional Fast Fourier Transform
(forward or inverse) of a two-dimensional double complex
array.
SUBROUTINE ZFFTZ2(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, *), Y(LDY, *)
DOUBLE PRECISION SCALE, TRIGS(*), WORK(*)
SUBROUTINE ZFFTZ2_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 SCALE, TRIGS(*), WORK(*)
DOUBLE COMPLEX X(LDX, *), Y(LDY, *)
F95 INTERFACE
SUBROUTINE FFT2(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
COMPLEX(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 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(8), INTENT(IN), OPTIONAL :: SCALE
COMPLEX(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 zfftz2_ (int *iopt, int *n1, int *n2, double *scale,
doublecomplex *x, int *ldx, doublecomplex *y, int
*ldy, double *trigs, int *ifac, double *work, int
*lwork, int *ierr);
void zfftz2_64_ (long *iopt, long *n1, long *n2, double
*scale, doublecomplex *x, long *ldx, doublecomplex
*y, long *ldy, double *trigs, long *ifac, double
*work, long *lwork, long *ierr);
zfftz2 initializes the trigonometric weight and factor
tables or computes the two-dimensional Fast Fourier
Transform (forward or inverse) of a two-dimensional double
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)
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 input data to be transformed.
LDX (input)
Leading dimension of X. LDX >= N1 Unchanged on
exit.
Y (output)
Y is a double complex array of dimensions (LDY,
N2) that contains the transform results. X and Y
can be the same array starting at the same memory
location, in which case the input data 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 = LDX Else LDY >= N1 Unchanged on exit.
TRIGS (input/output)
Double precision 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)
Double precision 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.