zfftd3(3P) Sun Performance Library zfftd3(3P)NAMEzfftd3 - initialize the trigonometric weight and factor tables or com‐
pute the three-dimensional inverse Fast Fourier Transform of a three-
dimensional double complex array.
SYNOPSIS
SUBROUTINE ZFFTD3(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
DOUBLE COMPLEX X(LDX1, LDX2, *)
DOUBLE PRECISION SCALE, TRIGS(*), WORK(*), Y(LDY1, LDY2, *)
SUBROUTINE ZFFTD3_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
DOUBLE COMPLEX X(LDX1, LDX2, *)
DOUBLE PRECISION SCALE, TRIGS(*), WORK(*), Y(LDY1, LDY2, *)
F95 INTERFACE
SUBROUTINE FFT3(IOPT, N1, [N2], [N3], [SCALE], X, [LDX1], LDX2, Y, [LDY1], LDY2, TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER, INTENT(IN) :: IOPT, N1, LDX2, LDY2
INTEGER, INTENT(IN), OPTIONAL :: N2, N3, LDX1, LDY1, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
COMPLEX(8), INTENT(IN), DIMENSION(:,:,:) :: X
REAL(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 FFT3_64(IOPT, N1, [N2], [N3], [SCALE], X, [LDX1], LDX2, Y, [LDY1], LDY2, TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER(8), INTENT(IN) :: IOPT, N1, LDX2, LDY2
INTEGER(8), INTENT(IN), OPTIONAL :: N2, N3, LDX1, LDY1, LWORK
REAL(8), INTENT(IN), OPTIONAL :: SCALE
COMPLEX(8), INTENT(IN), DIMENSION(:,:,:) :: X
REAL(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 zfftd3_ (int *iopt, int *n1, int *n2, int *n3, double *scale, dou‐
blecomplex *x, int *ldx1, int *ldx2, double *y, int *ldy1,
int *ldy2, double *trigs, int *ifac, double *work, int
*lwork, int *ierr);
void zfftd3_64_ (long *iopt, long *n1, long *n2, long *n3, double
*scale, doublecomplex *x, long *ldx1, long *ldx2, double *y,
long *ldy1, long *ldy2, double *trigs, long *ifac, double
*work, long *lwork, long *ierr);
PURPOSEzfftd3 initializes the trigonometric weight and factor tables or com‐
putes the three-dimensional inverse Fast Fourier Transform of a
three-dimensional double 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 inverse 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)
ARGUMENTS
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 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)
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 (LDX1, LDX2, N3)
that contains input data to be transformed.
LDX1 (input)
first dimension of X. LDX1 >= N1/2+1 Unchanged on exit.
LDX2 (input)
second dimension of X. LDX2 >= N2 Unchanged on exit.
Y (output)
Y is a double precision 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. Oth‐
erwise, 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 =
2*LDX1 Else LDY1 >= 2*LDX1 and LDY1 is even 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)
Double precision array of length 2*(N1+N2+N3) that contains
the trigonometric weights. The weights are computed when the
routine is called with IOPT = 0 and they are used in subse‐
quent 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 subse‐
quent calls when IOPT = 1. Unchanged on exit.
WORK (workspace)
Double precision 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 < N1/2+1)
-6 = (LDX2 < N2)
-7 = LDY1 not equal 2*LDX1 when X and Y are same array
-8 = (LDY1 < 2*LDX1) or (LDY1 is odd) when X and Y are not
same array
-9 = (LDY2 < N2) or (LDY2 not equal LDX2) when X and Y are
same array
-10 = (LWORK not equal 0) and ((LWORK < MAX(N,2*N2,2*N3) +
16*N3)*NCPUS)
-11 = memory allocation failed
SEE ALSO
fft
CAUTIONS
On exit, output subarray Y(1:LDY1, 1:N2, 1:N3) is overwritten.
6 Mar 2009 zfftd3(3P)
