cfftsm(3P) Sun Performance Library cfftsm(3P)NAMEcfftsm - initialize the trigonometric weight and factor tables or com‐
pute the one-dimensional inverse Fast Fourier Transform of a set of
complex data sequences stored in a two-dimensional array.
SYNOPSIS
SUBROUTINE CFFTSM(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
COMPLEX X(LDX, *)
REAL SCALE, Y(LDY, *), TRIGS(*), WORK(*)
SUBROUTINE CFFTSM_64(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER*8 IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
REAL SCALE, Y(LDY,*), TRIGS(*), WORK(*)
COMPLEX X(LDX, *)
F95 INTERFACE
SUBROUTINE FFTM(IOPT, N1, [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS,
IFAC, WORK, [LWORK], IERR)
INTEGER*4, INTENT(IN) :: IOPT, N1
INTEGER*4, INTENT(IN), OPTIONAL :: N2, LDX, LDY, 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 FFTM_64(IOPT, N1, [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER(8), INTENT(IN) :: IOPT, N1
INTEGER(8), INTENT(IN), OPTIONAL :: N2, LDX, LDY, 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 cfftsm_ (int *iopt, int *n1, int *n2, float *scale, complex *x,
int *ldx, float *y, int *ldy, float *trigs, int *ifac, float
*work, int *lwork, int *ierr);
void cfftsm_64_ (long *iopt, long *n1, long *n2, float *scale, complex
*x, long *ldx, float *y, long *ldy, float *trigs, long *ifac,
float *work, long *lwork, long *ierr);
PURPOSEcfftsm initializes the trigonometric weight and factor tables or com‐
putes the one-dimensional inverse Fast Fourier Transform of a set of
complex data sequences stored in a two-dimensional array:
N1-1
Y(k,l) = scale * SUM W*X(j,l)
j=0
where
k ranges from 0 to N1-1 and l ranges from 0 to N2-1
i = sqrt(-1)
isign = 1 for inverse transform
W = exp(isign*i*j*k*2*pi/N1)
In complex-to-real transform of length N1, the (N1/2+1) complex input
data points stored are the positive-frequency half of the spectrum of
the Discrete Fourier Transform. The other half can be obtained through
complex conjugation and therefore is not stored. Furthermore, due to
symmetries the imaginary of the component of X(0,0:N2-1) and
X(N1/2,0:N2-1) (if N1 is even in the latter) is assumed to be zero and
is not referenced.
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 input sequences. N1 is most
efficient when it is a product of small primes. N1 >= 0.
Unchanged on exit.
N2 (input)
Integer specifying number of input sequences. N2 >= 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 (LDX, N2) that contains
the sequences to be transformed stored in its columns in
X(0:N1/2, 0:N2-1).
LDX (input)
Leading dimension of X. LDX >= (N1/2+1) Unchanged on exit.
Y (output)
Y is a real array of dimensions (LDY, N2) that contains the
transform results of the input sequences in Y(0:N1-1,0:N2-1).
X and Y can be the same array starting at the same memory
location, in which case the input sequences are overwritten
by their transform results. Otherwise, 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 =
2*LDX Else LDY >= N1 Unchanged on exit.
TRIGS (input/output)
Real array of length 2*N1 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. Unchanged on exit.
IFAC (input/output)
Integer array of dimension at least 128 that contains the
factors of N1. 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 N1. 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 = (LDX < N1/2+1)
-5 = (LDY < N1) or (LDY not equal 2*LDX when X and Y are same
array)
-6 = (LWORK not equal 0) and (LWORK < N1)
-7 = memory allocation failed
SEE ALSO
fft
6 Mar 2009 cfftsm(3P)
