Contents
sfftc3 - initialize the trigonometric weight and factor
tables or compute the three-dimensional forward Fast Fourier
Transform of a three-dimensional complex array.
SUBROUTINE SFFTC3(IOPT, N1, N2, N3, SCALE, X, LDX1, LDX2, Y, LDY1, LDY2, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N1, N2, N3, LDX1, LDX2, LDY1, LDY2, IFAC(*),
LWORK, IERR
COMPLEX Y(LDY1, LDY2, *)
REAL X(LDX1, LDX2, *), SCALE, TRIGS(*), WORK(*)
SUBROUTINE SFFTC3_64(IOPT, N1, N2, N3, SCALE, X, LDX1, LDX2, Y, LDY1, LDY2, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER*8 IOPT, N1, N2, N3, LDX1, LDX2, LDY1, LDY2, IFAC(*),
LWORK, IERR
COMPLEX Y(LDY1, LDY2, *)
REAL X(LDX1, LDX2, *), SCALE, TRIGS(*), WORK(*)
F95 INTERFACE
SUBROUTINE FFT3(IOPT, [N1], [N2], [N3], [SCALE], X, [LDX1], LDX2, Y, [LDY1], LDY2, TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER*4, INTENT(IN) :: IOPT, LDX2, LDY2
INTEGER*4, INTENT(IN), OPTIONAL :: N1, N2, N3, LDX1, LDY1,
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 FFT3_64(IOPT, [N1], [N2], [N3], [SCALE], X, [LDX1], LDX2, Y, [LDY1], LDY2, TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER(8), INTENT(IN) :: IOPT, LDX2, LDY2
INTEGER(8), INTENT(IN), OPTIONAL :: N1, N2, N3, LDX1, LDY1,
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 sfftc3_ (int *iopt, int *n1, int *n2, int *n3, float
*scale, float *x, int *ldx1, int *ldx2, complex
*y, int *ldy1, int *ldy2, float *trigs, int *ifac,
float *work, int *lwork, int *ierr);
void sfftc3_64_ (long *iopt, long *n1, long *n2, long *n3,
float *scale, float *x, long *ldx1, long *ldx2,
complex *y, long *ldy1, long *ldy2, float *trigs,
long *ifac, float *work, long *lwork, long *ierr);
sfftc3 initializes the trigonometric weight and factor
tables or computes the three-dimensional forward Fast
Fourier Transform of a three-dimensional complex array.
N3-1 N2-1 N1-1
Y(k1,k2,k3) = scale * SUM SUM SUM W3*W2*W1*X(j1,j2,j3)
j3=0 j2=0 j1=0
where
k1 ranges from 0 to N1-1; k2 ranges from 0 to N2-1 and k3
ranges from 0 to N3-1
i = sqrt(-1)
isign = -1 for forward transform
W1 = exp(isign*i*j1*k1*2*pi/N1)
W2 = exp(isign*i*j2*k2*2*pi/N2)
W3 = exp(isign*i*j3*k3*2*pi/N3)
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 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.
N3 (input)
Integer specifying length of the transform in the
third dimension. N3 is most efficient when it is
a product of small primes. N3 >= 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 (LDX1, LDX2, N3)
that contains input data to be transformed. X can
be same array as Y.
LDX1 (input)
first dimension of X. If X is not same array as
Y, LDX1 >= N1 Else, LDX1 = 2*LDY1 Unchanged on
exit.
LDX2 (input)
second dimension of X. LDX2 >= N2 Unchanged on
exit.
Y (output)
Y is a complex array of dimensions (LDY1, LDY2,
N3) 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.
LDY1 (input)
first dimension of Y. LDY1 >= N1/2+1 Unchanged on
exit.
LDY2 (input)
second dimension of Y. If X and Y are the same
array, LDY2 = LDX2 Else LDY2 >= N2 Unchanged on
exit.
TRIGS (input/output)
Real array of length 2*(N1+N2+N3) that contains
the trigonometric weights. The weights are com-
puted 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 3*128 that
contains the factors of N1, N2 and N3. 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 (MAX(N,2*N2,2*N3)
+ 16*N3) * 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 or -1
-2 = N1 < 0
-3 = N2 < 0
-4 = N3 < 0
-5 = (LDX1 < N1) or (LDX not equal 2*LDY when X
and Y are same array)
-6 = (LDX2 < N2)
-7 = (LDY1 < N1/2+1)
-8 = (LDY2 < N2) or (LDY2 not equal LDX2 when X
and Y are same array)
-9 = (LWORK not equal 0) and (LWORK <
(MAX(N,2*N2,2*N3) + 16*N3)*NCPUS)
-10 = memory allocation failed
fft
This routine uses Y((N1/2+1)+1:LDY1,:,:) as scratch space.
Therefore, the original contents of this subarray will be
lost upon returning from routine while subarray
Y(1:N1/2+1,1:N2,1:N3) contains the transform results.