sdsdot()

real function sdsdot	(	integer	n,
		real	sb,
		real, dimension(*)	sx,
		integer	incx,
		real, dimension(*)	sy,
		integer	incy
	)

SDSDOT

Purpose:

   Compute the inner product of two vectors with extended
   precision accumulation.

   Returns S.P. result with dot product accumulated in D.P.
   SDSDOT = SB + sum for I = 0 to N-1 of SX(LX+I*INCX)*SY(LY+I*INCY),
   where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and LY is
   defined in a similar way using INCY.

Parameters

[in]	N	N is INTEGER number of elements in input vector(s)
[in]	SB	SB is REAL single precision scalar to be added to inner product
[in]	SX	SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) ) single precision vector with N elements
[in]	INCX	INCX is INTEGER storage spacing between elements of SX
[in]	SY	SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) ) single precision vector with N elements
[in]	INCY	INCY is INTEGER storage spacing between elements of SY

Author

Lawson, C. L., (JPL), Hanson, R. J., (SNLA),

Kincaid, D. R., (U. of Texas), Krogh, F. T., (JPL)

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Further Details:

    REFERENCES

    C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T.
    Krogh, Basic linear algebra subprograms for Fortran
    usage, Algorithm No. 539, Transactions on Mathematical
    Software 5, 3 (September 1979), pp. 308-323.

    REVISION HISTORY  (YYMMDD)

    791001  DATE WRITTEN
    890531  Changed all specific intrinsics to generic.  (WRB)
    890831  Modified array declarations.  (WRB)
    890831  REVISION DATE from Version 3.2
    891214  Prologue converted to Version 4.0 format.  (BAB)
    920310  Corrected definition of LX in DESCRIPTION.  (WRB)
    920501  Reformatted the REFERENCES section.  (WRB)
    070118  Reformat to LAPACK coding style

Definition at line 112 of file sdsdot.f.

*
*  -- Reference BLAS level1 routine --
*  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      REAL SB
      INTEGER INCX,INCY,N
*     ..
*     .. Array Arguments ..
      REAL SX(*),SY(*)
*     .. Local Scalars ..
      DOUBLE PRECISION DSDOT
      INTEGER I,KX,KY,NS
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC dble
*     ..
      dsdot = sb
      IF (n.LE.0) THEN
         sdsdot = real(dsdot)
         RETURN
      END IF
      IF (incx.EQ.incy .AND. incx.GT.0) THEN
*
*     Code for equal and positive increments.
*
         ns = n*incx
         DO i = 1,ns,incx
            dsdot = dsdot + dble(sx(i))*dble(sy(i))
         END DO
      ELSE
*
*     Code for unequal or nonpositive increments.
*
         kx = 1
         ky = 1
         IF (incx.LT.0) kx = 1 + (1-n)*incx
         IF (incy.LT.0) ky = 1 + (1-n)*incy
         DO i = 1,n
            dsdot = dsdot + dble(sx(kx))*dble(sy(ky))
            kx = kx + incx
            ky = ky + incy
         END DO
      END IF
      sdsdot = real(dsdot)
      RETURN
*
*     End of SDSDOT
*

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