Contents
cfftc3 - initialize the trigonometric weight and factor
tables or compute the three-dimensional Fast Fourier
Transform (forward or inverse) of a three-dimensional com-
plex array.
SUBROUTINE CFFTC3(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 X(LDX1, LDX2, *), Y(LDY1, LDY2, *)
REAL SCALE, TRIGS(*), WORK(*)
SUBROUTINE CFFTC3_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 X(LDX1, LDX2, *), Y(LDY1, LDY2, *)
REAL 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
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 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
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 cfftc3_ (int *iopt, int *n1, int *n2, int *n3, float
*scale, complex *x, int *ldx1, int *ldx2, complex
*y, int *ldy1, int *ldy2, float *trigs, int *ifac,
float *work, int *lwork, int *ierr);
void cfftc3_64_ (long *iopt, long *n1, long *n2, long *n3,
float *scale, complex *x, long *ldx1, long *ldx2,
complex *y, long *ldy1, long *ldy2, float *trigs,
long *ifac, float *work, long *lwork, long *ierr);
cfftc3 initializes the trigonometric weight and factor
tables or computes the three-dimensional Fast Fourier
Transform (forward or inverse) of a three-dimensional com-
plex 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 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)
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
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.
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 complex array of dimensions (LDX1, LDX2,
N3) that contains input data to be transformed.
LDX1 (input)
first dimension of X. LDX1 >= N1 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. If X and Y are the same
array, LDY1 = LDX1 Else LDY1 >= N1 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 or
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 fac-
tors 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(N,N2,N3) +
32*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, 1 or -1
-2 = N1 < 0
-3 = N2 < 0
-4 = N3 < 0
-5 = (LDX1 < N1)
-6 = (LDX2 < N2)
-7 = (LDY1 < N1) or (LDY1 not equal LDX1 when X
and Y are same array)
-8 = (LDY2 < N2) or (LDY2 not equal LDX2 when X
and Y are same array)
-9 = (LWORK not equal 0) and (LWORK <
(2*MAX(N,N2,N3) + 16*N3) * NCPUS)
-10 = memory allocation failed
fft
This routine uses Y(N1+1:LDY1,:,:) as scratch space. There-
fore, the original contents of this subarray will be lost
upon returning from routine while subarray Y(1:N1,1:N2,1:N3)
contains the transform results.