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Интерактивная система просмотра системных руководств (man-ов)

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dfft2b (3)
  • >> dfft2b (3) ( Solaris man: Библиотечные вызовы )
  • 
    NAME
         dfft2b - compute a periodic sequence from its Fourier  coef-
         ficients.   The  xFFT operations are unnormalized, so a call
         of xFFT2F followed by a call of  xFFT2B  will  multiply  the
         input sequence by M*N.
    
    SYNOPSIS
         SUBROUTINE RFFT2B (PLACE, M, N, RX, LDX,  RY,  LDY,  RWSAVE,
                   LWSAVE)
    
         SUBROUTINE DFFT2B (PLACE, M, N, DX, LDX,  DY,  LDY,  DWSAVE,
                   LWSAVE)
    
         SUBROUTINE CFFT2B (M, N, CX, LDX, RWSAVE, LWSAVE)
    
         SUBROUTINE ZFFT2B (M, N, ZX, LDX, DWSAVE, LWSAVE)
    
    
    
         #include <sunperf.h>
    
         void rfft2b (char place, int m, int n, float *rx,  int  ldx,
                   float *ry, int ldy, float *wsave, int lwsave);
    
         void dfft2b (char place, int m, int n, double *ry, int  ldx,
                   double *wsave, int lwsave);
    
         void cfft2b (int m, int n, complex  *cx,  int  ldx,  complex
                   *wsave, int lwsave);
    
         void zfft2b (int m, int n, doublecomplex *zx, int ldx, doub-
                   lecomplex *wsave, int lwsave);
    
    ARGUMENTS
         PLACE     Determines whether  an  in-place  or  out-of-place
                   transform  is  to  be performed.  'I' or 'i' if an
                   in-place transform is to be performed, 'O' or  'o'
                   if an out-of-place transform is to be performed.
    
         M         Number of rows to be transformed.   These  subrou-
                   tines  are  most  efficient when M is a product of
                   small primes.  M >= 0.
    
         N         Number of columns to be transformed.   These  sub-
                   routines are most efficient when N is a product of
                   small primes.  N >= 0.
    
         xX        On entry, a  two-dimensional  array  xX(M,N)  that
                   contains the sequences to be transformed.
    
         LDX       Leading dimension of the array containing the data
                   to be transformed.  LDX >= M.
    
         xY         On entry, the data to be transformed if PLACE  is
                    'O'  or  'o', otherwise this argument is ignored.
                    Undefined on exit.
    
         LDY        Leading dimension of  the  array  containing  the
                    data   to  be  transformed  in  the  out-of-place
                    transform case.  LDX >= M.
    
         xWSAVE    On entry, an array  with  dimension  of  at  least
                   LWSAVE.   xWSAVE  must  have  been  initialized by
                   xFFT2I.
    
         LWSAVE    Length of WSAVE.  LWSAVE >= (M+N+MAX(M,N)+45)  for
                   real  inputs or LWSAVE >= (2*(M+N+MAX(M,N)+45) for
                   complex inputs.
    
    SAMPLE PROGRAM
               PROGRAM TEST
               IMPLICIT NONE
         C
               INTEGER           LWSAVE, M, N
               PARAMETER        (LWSAVE = 4 * (M + N + K) + 45)
               PARAMETER        (M = 2)
               PARAMETER        (N = 4)
         C
               INTEGER           I, J
               REAL              PI, WSAVE(LWSAVE)
               REAL              X, Y
               COMPLEX           C(M,N)
         C
               EXTERNAL          CFFT2B, CFFT2F, CFFT2I
               INTRINSIC         ACOS, CMPLX, COS, SIN
         C
         C     Initialize the array C to a complex sequence.
         C
               PI = ACOS (-1.0)
               DO 110, J = 1, N
                 DO 100, I = 1, M
                   X = SIN ((I - 1.0) * 2.0 * PI / N)
                   Y = COS ((J - 1.0) * 2.0 * PI / M)
                   C(I,J) = CMPLX (X, Y)
           100   CONTINUE
           110 CONTINUE
         C
               PRINT 1000
               DO 200, I = 1, M
                 PRINT 1010, (C(I,J), J = 1, N)
           200 CONTINUE
               CALL CFFT2I (M, N, WSAVE)
               CALL CFFT2F (M, N, C, M, WSAVE, LWSAVE)
               PRINT 1020
               DO 300, I = 1, M
                 PRINT 1010, (C(I,J), J = 1, N)
           300 CONTINUE
               CALL CFFT2B (M, N, C, M, WSAVE, LWSAVE)
               PRINT 1030
               DO 400, I = 1, M
                 PRINT 1010, (C(I,J), J = 1, N)
           400 CONTINUE
         C
          1000 FORMAT (1X, 'Original Sequences:')
          1010 FORMAT (1X, 100(F4.1' +',F4.1,'i  '))
          1020 FORMAT (1X, 'Transformed Sequences:')
          1030 FORMAT (1X, 'Recovered Sequences:')
         C
               END
    
    SAMPLE OUTPUT
           0.0 + 1.0i   0.0 +-1.0i   0.0 + 1.0i   0.0 +-1.0i
           1.0 + 1.0i   1.0 +-1.0i   1.0 + 1.0i   1.0 +-1.0i
          Transformed Sequences:
           4.0 + 0.0i   0.0 + 0.0i   0.0 + 8.0i   0.0 + 0.0i
          -4.0 + 0.0i   0.0 + 0.0i   0.0 + 0.0i   0.0 + 0.0i
          Recovered Sequences:
           0.0 + 8.0i   0.0 +-8.0i   0.0 + 8.0i   0.0 +-8.0i
           8.0 + 8.0i   8.0 +-8.0i   8.0 + 8.0i   8.0 +-8.0i
    
    
    
    


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