dsdot()

double precision function dsdot	(	integer	n,
		real, dimension(*)	sx,
		integer	incx,
		real, dimension(*)	sy,
		integer	incy )

DSDOT

Purpose:

!>
!> Compute the inner product of two vectors with extended
!> precision accumulation and result.
!>
!> Returns D.P. dot product accumulated in D.P., for S.P. SX and SY
!> DSDOT = 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]	SX	!> SX is REAL array, dimension(N) !> single precision vector with N elements !>
[in]	INCX	!> INCX is INTEGER !> storage spacing between elements of SX !>
[in]	SY	!> SY is REAL array, dimension(N) !> single precision vector with N elements !>
[in]	INCY	!> INCY is INTEGER !> storage spacing between elements of SY !>

Returns

DSDOT

!>          DSDOT is DOUBLE PRECISION
!>         DSDOT  double precision dot product (zero if N.LE.0)
!> 

Author

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
!>  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 style (JL)
!> 

Definition at line 118 of file dsdot.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 ..
      INTEGER INCX,INCY,N
*     ..
*     .. Array Arguments ..
      REAL SX(*),SY(*)
*     ..
*
*  Authors:
*  ========
*  Lawson, C. L., (JPL), Hanson, R. J., (SNLA),
*  Kincaid, D. R., (U. of Texas), Krogh, F. T., (JPL)
*
*  =====================================================================
*
*     .. Local Scalars ..
      INTEGER I,KX,KY,NS
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC dble
*     ..
      dsdot = 0.0d0
      IF (n.LE.0) RETURN
      IF (incx.EQ.incy .AND. incx.GT.0) THEN
*
*     Code for equal, positive, non-unit 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
      RETURN
*
*     End of DSDOT
*

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