dsinqi(3P)

NAME

dsinqi - initialize the array xWSAVE, which is used in both xSINQF and xSINQB.

SYNOPSIS

SUBROUTINE SINQI (N, RWSAVE)

SUBROUTINE DSINQI (N, DWSAVE)

SUBROUTINE VSINQI (N, RWSAVE)

SUBROUTINE VDSINQI (N, DWSAVE)

#include <sunperf.h>

void sinqi (int n, float ∗rwsave) ;

void dsinqi (int n, double ∗dwsave) ;

void vsinqi (int n, float ∗rwsave) ;

void vdsinqi (int n, float ∗dwsave) ;

ARGUMENTS

N Length of the sequence to be transformed. The method is most efficient when N is a product of small primes.

xWSAVE On entry, an array with a dimension of at least (3 ∗ N + 15) for scalar subroutines or (2 ∗ N + 15) for vector subroutines. The same work array can be used for both xSINQF and xSINQB 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 xCSINF or xCSINB as long as N and xWSAVE remain unchanged, thus subsequent transforms can be obtained faster than the first.

SAMPLE PROGRAM

      PROGRAM TEST
      IMPLICIT NONE
C
      INTEGER            N
      PARAMETER         (N = 6)
C
      INTEGER            I
      REAL               PI, WSAVE(3 ∗ N + 15), X(N)
C
      EXTERNAL           SINQB, SINQF, SINQI
      INTRINSIC          ACOS, SIN
C
C     Initialize array X to a real odd quarter-wave sequence,
C     that is,it can be expanded in terms of a sine series with
C     only odd wave number.
C
      PI = ACOS (-1.0)
      DO 100, I=1, N
        X(I) = 40.0 ∗ SIN (I ∗ PI / (2.0 ∗ N))
100 CONTINUE
C
      PRINT 1000
      PRINT 1010, (X(I), I = 1, N)
      CALL SINQI (N, WSAVE)
      CALL SINQF (N, X, WSAVE)
      PRINT 1020
      PRINT 1010, (X(I), I = 1, N)
      CALL SINQB(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: ’)
C
      END

SAMPLE OUTPUT

Original Sequence:
10.4 20.0 28.3 34.6 38.6 40.0
Transformed Sequence:
240.0 0.0 0.0 0.0 0.0 0.0
Recovered Sequence:
248.5 480.0 678.8 831.4 927.3 960.0