vdsinqi(l) — SunSoft Performance Library

NAME

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

SYNOPSIS

CALL SINQI (N, RWSAVE)

CALL DSINQI (N, DWSAVE)

CALL VSINQI (N, RWSAVE)

CALL VDSINQI (N, DWSAVE)

ARGUMENTS

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

xWSAVEOn 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