sfftcm(3P) Sun Performance Library sfftcm(3P)NAMEsfftcm - initialize the trigonometric weight and factor tables or com‐
pute the one-dimensional forward Fast Fourier Transform of a set of
real data sequences stored in a two-dimensional array.
SYNOPSIS
SUBROUTINE SFFTCM(IOPT, N1, N2, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR)
INTEGER IOPT, N1, N2, LDX, LDY, IFAC(*), LWORK, IERR
REAL X(LDX, *), SCALE, TRIGS(*), WORK(*)
COMPLEX Y(LDY, *)
SUBROUTINE SFFTCM_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 X(LDX, *), SCALE, TRIGS(*), WORK(*)
COMPLEX Y(LDY, *)
F95 INTERFACE
SUBROUTINE FFTM(IOPT, [N1], [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS,
IFAC, WORK, [LWORK], IERR)
INTEGER*4, INTENT(IN) :: IOPT
INTEGER*4, INTENT(IN), OPTIONAL :: N1, N2, LDX, LDY, 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 FFTM_64(IOPT, [N1], [N2], [SCALE], X, [LDX], Y, [LDY], TRIGS, IFAC, WORK, [LWORK], IERR)
INTEGER(8), INTENT(IN) :: IOPT
INTEGER(8), INTENT(IN), OPTIONAL :: N1, N2, LDX, LDY, 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 sfftcm_ (int *iopt, int *n1, int *n2, float *scale, float *x, int
*ldx, complex *y, int *ldy, float *trigs, int *ifac, float
*work, int *lwork, int *ierr);
void sfftcm_64_ (long *iopt, long *n1, long *n2, float *scale, float
*x, long *ldx, complex *y, long *ldy, float *trigs, long
*ifac, float *work, long *lwork, long *ierr);
PURPOSEsfftcm initializes the trigonometric weight and factor tables or com‐
putes the one-dimensional forward Fast Fourier Transform of a set of
real 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 forward transform
W = exp(isign*i*j*k*2*pi/N1)
In real-to-complex transform of length N1, the (N1/2+1) complex output
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.
ARGUMENTS
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 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 real array of dimensions (LDX, N2) that contains the
sequences to be transformed stored in its columns.
LDX (input)
Leading dimension of X. If X and Y are the same array, LDX =
2*LDY Else LDX >= N1 Unchanged on exit.
Y (output)
Y is a complex array of dimensions (LDY, N2) that contains
the transform results of the input sequences. 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. LDY >= N1/2 + 1 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) or (LDX not equal 2*LDY when X and Y are same
array)
-4 = (LDY < N1/2 + 1)
-6 = (LWORK not equal 0) and (LWORK < N1)
-7 = memory allocation failed
SEE ALSO
fft
6 Mar 2009 sfftcm(3P)
