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NAME
     dcost - compute the discrete Fourier cosine transform of  an
     even   sequence.   The  xCOST  transforms  are  unnormalized
     inverses of themselves, so  a  call  of  xCOST  followed  by
     another  call of xCOST will multiply the input sequence by 2
     * (N-1).  The VxCOST transforms are normalized, so a call of
     VxCOST followed by a call of VxCOST will return the original
     sequence.

SYNOPSIS
     SUBROUTINE COST (N, RX, RWSAVE)

     SUBROUTINE DCOST (N, DX, DWSAVE)

     SUBROUTINE VCOST (M,N, RX, RXT, MDIMX, RWSAVE)

     SUBROUTINE VDCOST (M,N, DX, DXT, MDIMX, DWSAVE)



     #include <sunperf.h>

     void cost (int n, float *sx, float *wsave) ;

     void dcost (int n, double *dx, double *wsave)

     void vcost(int m, int n, float *sx, int mdimx, float *wsave)

     void vdcost(int m, int n,  double  *dx,  int  mdimx,  double
               *wsave)

ARGUMENTS
     M         (For vector operations only.)
               The number of sequences to be transformed.   M  >=
               0.

     N         Length of the sequence to be  transformed.   These
               subroutines  are  most  efficient  when N - 1 is a
               product of small primes.  N >= 2.

     xX        On entry, an array  of  length  N  containing  the
               sequence  to  be  transformed.  For VxCOST, a real
               two- dimensional array with dimensions of (MDIMX x
               (N+1))  whose  rows  contain  the  sequences to be
               transformed.  On exit, the cosine transform of the
               input.

     xXT       (For vector operations only.)
               A real two-dimensional work array with  dimensions
               of (MDIMX x (N-1)).

     MDIMX     (For vector operations only.)
               Leading dimension of the  arrays  xX  and  xXT  as
               specified in a dimension or type statement.

     MDIMX     >= M.  xWSAVE    On entry, an array with dimension
               of  at  least  (3 * N + 15), initialized by xCOSTI
               or VxCOSTI.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER         N
           PARAMETER      (N = 9)
     C
           INTEGER         I
           REAL            PI, X(N), WSAVE(3 * N + 15)
     C
           EXTERNAL        COST, COSTI
           INTRINSIC       ACOS, COS
     C
     C     Initialize the array X to an even sequence, that is, it can be
     C     expanded in terms of a trigonometric series that contains only
     C     cosine terms.
     C
           PI = ACOS (-1.0)
           DO 100, I=1, N
             X(I) = COS ((I - 1.0) * 2.0 * PI / (N - 1.0))
       100 CONTINUE
     C
           CALL COSTI (N, WSAVE)
           PRINT 1000
           PRINT 1010, (X(I), I = 1, N)
           CALL COST (N, X, WSAVE)
           PRINT 1020
           PRINT 1010, (X(I), I = 1, N)
           CALL COST (N, X, WSAVE)
           PRINT 1030
           PRINT 1010, (X(I), I = 1, N)
     C
      1000 FORMAT (1X, 'Original Sequence: ')
      1010 FORMAT (1X, 100(F5.1, 1X))
      1020 FORMAT (1X, 'Transformed Sequence: ')
      1030 FORMAT (1X, 'Recovered Sequence: ')
           END

SAMPLE OUTPUT
      Original Sequence:
        1.0   0.7   0.0  -0.7  -1.0  -0.7   0.0   0.7   1.0
      Transformed Sequence:
        0.0   0.0   8.0   0.0   0.0   0.0   0.0   0.0   0.0
      Recovered Sequence:
       16.0  11.3   0.0 -11.3 -16.0 -11.3   0.0  11.3  16.0

Партнёры:

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