DE01PD

Convolution or deconvolution of two real signals using Hartley transform

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

  To compute the convolution or deconvolution of two real signals
  A and B using the Hartley transform.

Specification
      SUBROUTINE DE01PD( CONV, WGHT, N, A, B, W, INFO )
C     .. Scalar Arguments ..
      CHARACTER         CONV, WGHT
      INTEGER           INFO, N
C     .. Array Arguments ..
      DOUBLE PRECISION  A(*), B(*), W(*)

Arguments

Mode Parameters

  CONV    CHARACTER*1
          Indicates whether convolution or deconvolution is to be
          performed as follows:
          = 'C':  Convolution;
          = 'D':  Deconvolution.

  WGHT    CHARACTER*1
          Indicates whether the precomputed weights are available
          or not, as follows:
          = 'A':  available;
          = 'N':  not available.
          Note that if N > 1 and WGHT = 'N' on entry, then WGHT is
          set to 'A' on exit.

Input/Output Parameters
  N       (input) INTEGER
          The number of samples.  N must be a power of 2.  N >= 0.

  A       (input/output) DOUBLE PRECISION array, dimension (N)
          On entry, this array must contain the first signal.
          On exit, this array contains the convolution (if
          CONV = 'C') or deconvolution (if CONV = 'D') of the two
          signals.

  B       (input) DOUBLE PRECISION array, dimension (N)
          On entry, this array must contain the second signal.
          NOTE that this array is overwritten.

  W       (input/output) DOUBLE PRECISION array,
                         dimension (N - LOG2(N))
          On entry with WGHT = 'A', this array must contain the long
          weight vector computed by a previous call of this routine
          or of the SLICOT Library routine DG01OD.f, with the same
          value of N. If WGHT = 'N', the contents of this array on
          entry is ignored.
          On exit, this array contains the long weight vector.

Error Indicator
  INFO    INTEGER
          = 0:  successful exit;
          < 0:  if INFO = -i, the i-th argument had an illegal
                value.

Method
  This routine computes the convolution or deconvolution of two
  real signals A and B using three scrambled Hartley transforms
  (SLICOT Library routine DG01OD).

References
  [1] Van Loan, Charles.
      Computational frameworks for the fast Fourier transform.
      SIAM, 1992.

Numerical Aspects
  The algorithm requires O(N log(N)) floating point operations.

Further Comments
  None
Example

Program Text

*     DE01PD EXAMPLE PROGRAM TEXT
*     Copyright (c) 2002-2017 NICONET e.V.
*
*     .. Parameters ..
      INTEGER          NIN, NOUT
      PARAMETER        ( NIN = 5, NOUT = 6 )
      INTEGER          NMAX
      PARAMETER        ( NMAX = 128 )
*     .. Local Scalars ..
      INTEGER          I, INFO, N
      CHARACTER*1      CONV, WGHT
*     .. Local Arrays ..
      DOUBLE PRECISION A(NMAX), B(NMAX), W(NMAX)
*     .. External Functions ..
      LOGICAL          LSAME
      EXTERNAL         LSAME
*     .. External Subroutines ..
      EXTERNAL         DE01PD
*     .. Executable Statements ..
*
      WRITE ( NOUT, FMT = 99999 )
*     Skip the heading in the data file and read the data.
      READ ( NIN, FMT = '()' )
      READ ( NIN, FMT = * ) N, CONV, WGHT
      IF ( N.LT.0 .OR. N.GT.NMAX ) THEN
         WRITE ( NOUT, FMT = 99994 ) N
      ELSE
         READ ( NIN, FMT = * ) ( A(I), B(I), I = 1,N )
*        Perform convolution on A and B.
         CALL DE01PD( CONV, WGHT, N, A, B, W, INFO )
*
         IF ( INFO.NE.0 ) THEN
            WRITE ( NOUT, FMT = 99998 ) INFO
         ELSE
            IF ( LSAME( CONV, 'C' ) ) THEN
               WRITE ( NOUT, FMT = 99997 )
            ELSE
               WRITE ( NOUT, FMT = 99996 )
            END IF
            DO 20 I = 1, N
               WRITE ( NOUT, FMT = 99995 ) I, A(I)
   20       CONTINUE
         END IF
      END IF
      STOP
*
99999 FORMAT (' DE01PD EXAMPLE PROGRAM RESULTS',/1X)
99998 FORMAT (' INFO on exit from DE01PD = ',I2)
99997 FORMAT ('   Convolution ',//'   i    A(i)',/)
99996 FORMAT ('   Deconvolution ',//'   i    A(i)',/)
99995 FORMAT (I4,1X,F8.4)
99994 FORMAT (/' N is out of range.',/' N = ',I5)
      END
Program Data
 DE01PD EXAMPLE PROGRAM DATA
   8     C     N
   0.4862   0.2288
   0.1948   0.3671
   0.5788   0.6417
  -0.5861   0.3875
   0.8254   0.2380
   0.1815   0.4682
   0.2904   0.5312
  -0.3599   0.6116
Program Results
 DE01PD EXAMPLE PROGRAM RESULTS

   Convolution 

   i    A(i)

   1   0.5844
   2   0.5769
   3   0.6106
   4   1.0433
   5   0.6331
   6   0.4531
   7   0.7027
   8   0.9929

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