*DECK SDSDOT
REAL FUNCTION SDSDOT (N, SB, SX, INCX, SY, INCY)
C***BEGIN PROLOGUE SDSDOT
C***PURPOSE Compute the inner product of two vectors with extended
C precision accumulation.
C***LIBRARY SLATEC (BLAS)
C***CATEGORY D1A4
C***TYPE SINGLE PRECISION (SDSDOT-S, CDCDOT-C)
C***KEYWORDS BLAS, DOT PRODUCT, INNER PRODUCT, LINEAR ALGEBRA, VECTOR
C***AUTHOR Lawson, C. L., (JPL)
C Hanson, R. J., (SNLA)
C Kincaid, D. R., (U. of Texas)
C Krogh, F. T., (JPL)
C***DESCRIPTION
C
C B L A S Subprogram
C Description of Parameters
C
C --Input--
C N number of elements in input vector(s)
C SB single precision scalar to be added to inner product
C SX single precision vector with N elements
C INCX storage spacing between elements of SX
C SY single precision vector with N elements
C INCY storage spacing between elements of SY
C
C --Output--
C SDSDOT single precision dot product (SB if N .LE. 0)
C
C Returns S.P. result with dot product accumulated in D.P.
C SDSDOT = SB + sum for I = 0 to N-1 of SX(LX+I*INCX)*SY(LY+I*INCY),
C where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and LY is
C defined in a similar way using INCY.
C
C***REFERENCES C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T.
C Krogh, Basic linear algebra subprograms for Fortran
C usage, Algorithm No. 539, Transactions on Mathematical
C Software 5, 3 (September 1979), pp. 308-323.
C***ROUTINES CALLED (NONE)
C***REVISION HISTORY (YYMMDD)
C 791001 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890831 Modified array declarations. (WRB)
C 890831 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 920310 Corrected definition of LX in DESCRIPTION. (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE SDSDOT
REAL SX(*), SY(*), SB
DOUBLE PRECISION DSDOT
C***FIRST EXECUTABLE STATEMENT SDSDOT
DSDOT = SB
IF (N .LE. 0) GO TO 30
IF (INCX.EQ.INCY .AND. INCX.GT.0) GO TO 40
C
C Code for unequal or nonpositive increments.
C
KX = 1
KY = 1
IF (INCX .LT. 0) KX = 1+(1-N)*INCX
IF (INCY .LT. 0) KY = 1+(1-N)*INCY
DO 10 I = 1,N
DSDOT = DSDOT + DBLE(SX(KX))*DBLE(SY(KY))
KX = KX + INCX
KY = KY + INCY
10 CONTINUE
30 SDSDOT = DSDOT
RETURN
C
C Code for equal and positive increments.
C
40 NS = N*INCX
DO 50 I = 1,NS,INCX
DSDOT = DSDOT + DBLE(SX(I))*DBLE(SY(I))
50 CONTINUE
SDSDOT = DSDOT
RETURN
END