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NAME
     cffti - initialize the array xWSAVE, which is used  in  both
     xFFTF and xFFTB.

SYNOPSIS
     SUBROUTINE RFFTI(N, RWSAVE)

     SUBROUTINE DFFTI(N, DWSAVE)

     SUBROUTINE CFFTI(N, RWSAVE)

     SUBROUTINE ZFFTI(N, DWSAVE)

     SUBROUTINE VRFFTI(N, RWSAVE)

     SUBROUTINE VDFFTI(N, DWSAVE)



     #include <sunperf.h>

     void rffti (int n, float *wsave);

     void dffti (int n, double *wsave);

     void cffti (int n, complex *wsave);

     void zffti (int n, doublecomplex *wsave);

     void vrffti (int n, float *wsave);

     void vdffti (int n, double *wsave);

ARGUMENTS
     N         Length of the sequence to be transformed.  N >= 0.

     xWSAVE    On entry, an array with  a  dimension  for  scalar
               subroutines  of  at  least  (2  * N + 15) for real
               inputs or (4 * N + 15) for  complex  inputs.   For
               vector subroutines, the dimension is at least (N +
               15).  The same work array can  be  used  for  both
               xFFTF  and  xFFTB  as long as N remains unchanged.
               Different xWSAVE arrays are required for different
               values of N.  This initialization does not have to
               be repeated between calls to  xFFTF  or  xFFTB  as
               long as N and xWSAVE remain unchanged, thus subse-
               quent transforms can be obtained faster  than  the
               first.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE

     C
           INTEGER          N
           PARAMETER       (N = 9)
     C
           INTEGER          I
           REAL             PI, R(N), WSAVE(2 * N + 15)
     C
           EXTERNAL         RFFTB, RFFTF, RFFTI
           INTRINSIC        ACOS, SIN
     C
     C     Initialize array to a real sequence.
     C
           PI = ACOS (-1.0)
           DO 100, I=1, N
             R(I) = 3.0 + SIN ((I - 1.0) * 2.0 * PI / N)
       100 CONTINUE
     C
           PRINT 1000
           PRINT 1010, (R(I), I = 1, N)
           CALL RFFTI (N, WSAVE)
           CALL RFFTF (N, R, WSAVE)
           PRINT 1020
           PRINT 1010, (R(I), I = 1, N)
           CALL RFFTB (N, R, WSAVE)
           PRINT 1030
           PRINT 1010, (R(I), I = 1, N)
     C
      1000 FORMAT (1X, 'Original Sequence: ')
      1010 FORMAT (1X, 100(F4.1, 1X))
      1020 FORMAT (1X, 'Transformed Sequence: ')
      1030 FORMAT (1X, 'Recovered Sequence: ')
     C
           END


SAMPLE OUTPUT
      Original Sequence:
       3.0  3.6  4.0  3.9  3.3  2.7  2.1  2.0  2.4
      Transformed Sequence:
      27.0  0.0 -4.5  0.0  0.0  0.0  0.0  0.0  0.0
      Recovered Sequence:
      27.0 32.8 35.9 34.8 30.1 23.9 19.2 18.1 21.2

Партнёры:

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