*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