cffts2 - pute the two-dimensional inverse Fast Fourier Transform of a two-dimen- sional complex array.
SUBROUTINE CFFTS2(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER IOPT, M, N, LDX, LDY, IFAC(*), LWORK, IERR COMPLEX X(LDX, *) REAL SCALE, Y(LDY, *), TRIGS(*), WORK(*) SUBROUTINE CFFTS2_64(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER*8 IOPT, M, N, LDX, LDY, IFAC(*), LWORK, IERR COMPLEX X(LDX, *) REAL SCALE, Y(LDY, *), TRIGS(*), WORK(*) F95 INTERFACE SUBROUTINE FFT2(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, & IFAC, WORK, LWORK, IERR) INTEGER*4, INTENT(IN) :: IOPT, M INTEGER*4, INTENT(IN), OPTIONAL :: N, 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 FFT2_64(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER(8), INTENT(IN) :: IOPT, M INTEGER(8), INTENT(IN), OPTIONAL :: N, 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 cffts2_ (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 cffts2_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);
Oracle Solaris Studio Performance Library cffts2(3P) NAME cffts2 - initialize the trigonometric weight and factor tables or com- pute the two-dimensional inverse Fast Fourier Transform of a two-dimen- sional complex array. SYNOPSIS SUBROUTINE CFFTS2(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER IOPT, M, N, LDX, LDY, IFAC(*), LWORK, IERR COMPLEX X(LDX, *) REAL SCALE, Y(LDY, *), TRIGS(*), WORK(*) SUBROUTINE CFFTS2_64(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER*8 IOPT, M, N, LDX, LDY, IFAC(*), LWORK, IERR COMPLEX X(LDX, *) REAL SCALE, Y(LDY, *), TRIGS(*), WORK(*) F95 INTERFACE SUBROUTINE FFT2(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, & IFAC, WORK, LWORK, IERR) INTEGER*4, INTENT(IN) :: IOPT, M INTEGER*4, INTENT(IN), OPTIONAL :: N, 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 FFT2_64(IOPT, M, N, SCALE, X, LDX, Y, LDY, TRIGS, IFAC, WORK, LWORK, IERR) INTEGER(8), INTENT(IN) :: IOPT, M INTEGER(8), INTENT(IN), OPTIONAL :: N, 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 cffts2_ (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 cffts2_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); PURPOSE cffts2 initializes the trigonometric weight and factor tables or com- putes the two-dimensional inverse Fast Fourier Transform of a two- dimensional complex array. In computing the two-dimensional FFT, one- dimensional FFTs are computed along the rows of the input array. One- dimensional FFTs are then computed along the columns of the intermedi- ate results. M-1 N-1 Y(k1,k2) = scale * SUM SUM W2*W1*X(j1,j2) j1=0 j2=0 where k1 ranges from 0 to M-1 and k2 ranges from 0 to N-1 i = sqrt(-1) isign = 1 for inverse transform W1 = exp(isign*i*j1*k1*2*pi/M) W2 = exp(isign*i*j2*k2*2*pi/N) In complex-to-real transform of length M, the (M/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. 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 M (input) Integer specifying length of the transform in the first dimension. M is most efficient when it is a product of small primes. M >= 0. Unchanged on exit. N (input) Integer specifying length of the transform in the second dimension. N is most efficient when it is a product of small primes. N >= 0. Unchanged on exit. SCALE (input) Real scalar by which transform results are scaled. Unchanged on exit. X (input) X is a complex array of dimensions (LDX, N) that contains input data to be transformed. LDX (input) Leading dimension of X. LDX >= (M/2 + 1) Unchanged on exit. Y (output) Y is a real array of dimensions (LDY, N) 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. 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 >= 2*LDX and LDY must be even. Unchanged on exit. TRIGS (input/output) Real array of length 2*(M+N) 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 2*128 that contains the factors of M and N. The factors are computed when the rou- tine 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 MAX(M,2*N)*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, 1 -2 = M < 0 -3 = N < 0 -4 = (LDX < M/2+1) -5 = LDY not equal 2*LDX when X and Y are same array -6 = (LDY < 2*LDX or LDY odd) when X and Y are same array -7 = (LWORK not equal 0) and (LWORK < MAX(M,2*N)*NCPUS) -8 = memory allocation failed SEE ALSO fft CAUTIONS Y(M+1:LDY,:) is used as scratch space. Upon returning, the original contents of Y(M+1:LDY,:) will be lost, whereas Y(1:M,1:N) contains the transform results. 7 Nov 2015 cffts2(3P)