cffts3(3P) Sun Performance Library cffts3(3P)NAMEcffts3 - initialize the trigonometric weight and factor tables or com‐
pute the three-dimensional inverse Fast Fourier Transform of a three-
dimensional complex array.
SYNOPSIS
SUBROUTINE CFFTS3(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, *)
REAL SCALE, TRIGS(*), WORK(*), Y(LDY1, LDY2, *)
SUBROUTINE CFFTS3_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, *)
REAL 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*4, INTENT(IN) :: IOPT, N1, LDX2, LDY2
INTEGER*4, INTENT(IN), OPTIONAL :: N2, N3, LDX1, LDY1, LWORK
REAL, INTENT(IN), OPTIONAL :: SCALE
COMPLEX, INTENT(IN), DIMENSION(:,:,:) :: X
REAL, 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, N1, LDX2, LDY2
INTEGER(8), INTENT(IN), OPTIONAL :: N2, N3, LDX1, LDY1, LWORK
REAL, INTENT(IN), OPTIONAL :: SCALE
COMPLEX, INTENT(IN), DIMENSION(:,:,:) :: X
REAL, 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 cffts3_ (int *iopt, int *n1, int *n2, int *n3, float *scale, com‐
plex *x, int *ldx1, int *ldx2, float *y, int *ldy1, int
*ldy2, float *trigs, int *ifac, float *work, int *lwork, int
*ierr);
void cffts3_64_ (long *iopt, long *n1, long *n2, long *n3, float
*scale, complex *x, long *ldx1, long *ldx2, float *y, long
*ldy1, long *ldy2, float *trigs, long *ifac, float *work,
long *lwork, long *ierr);
PURPOSEcffts3 initializes the trigonometric weight and factor tables or com‐
putes the three-dimensional inverse 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 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)
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 con‐
tains 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 real array of dimensions (LDY1, LDY2, N3) that con‐
tains 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. Otherwise,
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)
Real array of length 2*(N1+N2+N3) that contains the trigono‐
metric weights. The weights are computed 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 subse‐
quent 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 < N1/2+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
This routine uses Y(N1+1:LDY1,:,:) as scratch space. Therefore, 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.
6 Mar 2009 cffts3(3P)
