zfftd - pute the inverse Fast Fourier Transform of a double complex sequence.
SUBROUTINE ZFFTD(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER IOPT, N, IFAC(*), LWORK, IERR DOUBLE COMPLEX X(*) DOUBLE PRECISION SCALE, Y(*), TRIGS(*), WORK(*) SUBROUTINE ZFFTD_64(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER*8 IOPT, N, IFAC(*), LWORK, IERR DOUBLE PRECISION SCALE, Y(*), TRIGS(*), WORK(*) DOUBLE COMPLEX X(*) F95 INTERFACE SUBROUTINE FFT(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER, INTENT(IN) :: IOPT, N INTEGER, INTENT(IN), OPTIONAL :: 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 FFT_64(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER(8), INTENT(IN) :: IOPT, N INTEGER(8), INTENT(IN), OPTIONAL :: 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 zfftd_ (int *iopt, int *n, double *scale, doublecomplex *x, double *y, double *trigs, int *ifac, double *work, int *lwork, int *ierr); void zfftd_64_ (long *iopt, long *n, double *scale, doublecomplex *x, double *y, double *trigs, long *ifac, double *work, long *lwork, long *ierr);
Oracle Solaris Studio Performance Library zfftd(3P) NAME zfftd - initialize the trigonometric weight and factor tables or com- pute the inverse Fast Fourier Transform of a double complex sequence. SYNOPSIS SUBROUTINE ZFFTD(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER IOPT, N, IFAC(*), LWORK, IERR DOUBLE COMPLEX X(*) DOUBLE PRECISION SCALE, Y(*), TRIGS(*), WORK(*) SUBROUTINE ZFFTD_64(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER*8 IOPT, N, IFAC(*), LWORK, IERR DOUBLE PRECISION SCALE, Y(*), TRIGS(*), WORK(*) DOUBLE COMPLEX X(*) F95 INTERFACE SUBROUTINE FFT(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER, INTENT(IN) :: IOPT, N INTEGER, INTENT(IN), OPTIONAL :: 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 FFT_64(IOPT, N, SCALE, X, Y, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER(8), INTENT(IN) :: IOPT, N INTEGER(8), INTENT(IN), OPTIONAL :: 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 zfftd_ (int *iopt, int *n, double *scale, doublecomplex *x, double *y, double *trigs, int *ifac, double *work, int *lwork, int *ierr); void zfftd_64_ (long *iopt, long *n, double *scale, doublecomplex *x, double *y, double *trigs, long *ifac, double *work, long *lwork, long *ierr); PURPOSE zfftd initializes the trigonometric weight and factor tables or com- putes the inverse Fast Fourier Transform of a double complex sequence as follows: N-1 Y(k) = scale * SUM W*X(j) j=0 where k ranges from 0 to N-1 i = sqrt(-1) isign = 1 for inverse transform or -1 for forward transform W = exp(isign*i*j*k*2*pi/N) In complex-to-real transform of length N, the (N/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) and X(N/2) (if N 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 N (input) Integer specifying length of the input sequence X. N is most efficient when it is a product of small primes. N >= 0. Unchanged on exit. SCALE (input) Double precision scalar by which transform results are scaled. Unchanged on exit. X (input) On entry, X is a double complex array whose first (N/2+1) elements are the input sequence to be transformed. Y (output) Double precision array of dimension at least N that contains the transform results. X and Y may be the same array start- ing at the same memory location. Otherwise, it is assumed that there is no overlap between X and Y in memory. TRIGS (input/output) Double precision array of length 2*N 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 128 that contains the factors of N. The factors are computed when the routine is called with IOPT = 0 and they are used in subsequent calls where IOPT = 1. Unchanged on exit. WORK (workspace) Double precision array of dimension at least N. 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 = N < 0 -3 = (LWORK is not 0) and (LWORK is less than N) -4 = memory allocation for workspace failed SEE ALSO fft 7 Nov 2015 zfftd(3P)