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Annotation of rpl/lapack/blas/dsdot.f, revision 1.1

1.1     ! bertrand    1:       DOUBLE PRECISION FUNCTION DSDOT(N,SX,INCX,SY,INCY)
        !             2: *     .. Scalar Arguments ..
        !             3:       INTEGER INCX,INCY,N
        !             4: *     ..
        !             5: *     .. Array Arguments ..
        !             6:       REAL SX(*),SY(*)
        !             7: *     ..
        !             8: *
        !             9: *  AUTHORS
        !            10: *  =======
        !            11: *  Lawson, C. L., (JPL), Hanson, R. J., (SNLA), 
        !            12: *  Kincaid, D. R., (U. of Texas), Krogh, F. T., (JPL)
        !            13: *
        !            14: *  Purpose
        !            15: *  =======
        !            16: *  Compute the inner product of two vectors with extended
        !            17: *  precision accumulation and result.
        !            18: *
        !            19: *  Returns D.P. dot product accumulated in D.P., for S.P. SX and SY
        !            20: *  DSDOT = sum for I = 0 to N-1 of  SX(LX+I*INCX) * SY(LY+I*INCY),
        !            21: *  where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and LY is
        !            22: *  defined in a similar way using INCY.
        !            23: *
        !            24: *  Arguments
        !            25: *  =========
        !            26: *
        !            27: *  N      (input) INTEGER
        !            28: *         number of elements in input vector(s)
        !            29: *
        !            30: *  SX     (input) REAL array, dimension(N)
        !            31: *         single precision vector with N elements
        !            32: *
        !            33: *  INCX   (input) INTEGER
        !            34: *          storage spacing between elements of SX
        !            35: *
        !            36: *  SY     (input) REAL array, dimension(N)
        !            37: *         single precision vector with N elements
        !            38: *
        !            39: *  INCY   (input) INTEGER
        !            40: *         storage spacing between elements of SY
        !            41: *
        !            42: *  DSDOT  (output) DOUBLE PRECISION
        !            43: *         DSDOT  double precision dot product (zero if N.LE.0)
        !            44: *
        !            45: *  Further Details
        !            46: *  ===============
        !            47: *
        !            48: *  REFERENCES
        !            49: *      
        !            50: *  C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T.
        !            51: *  Krogh, Basic linear algebra subprograms for Fortran
        !            52: *  usage, Algorithm No. 539, Transactions on Mathematical
        !            53: *  Software 5, 3 (September 1979), pp. 308-323.
        !            54: *
        !            55: *  REVISION HISTORY  (YYMMDD)
        !            56: *
        !            57: *  791001  DATE WRITTEN
        !            58: *  890831  Modified array declarations.  (WRB)
        !            59: *  890831  REVISION DATE from Version 3.2
        !            60: *  891214  Prologue converted to Version 4.0 format.  (BAB)
        !            61: *  920310  Corrected definition of LX in DESCRIPTION.  (WRB)
        !            62: *  920501  Reformatted the REFERENCES section.  (WRB)
        !            63: *  070118  Reformat to LAPACK style (JL)
        !            64: *
        !            65: *  =====================================================================
        !            66: *
        !            67: *     .. Local Scalars ..
        !            68:       INTEGER I,KX,KY,NS
        !            69: *     ..
        !            70: *     .. Intrinsic Functions ..
        !            71:       INTRINSIC DBLE
        !            72: *     ..
        !            73:       DSDOT = 0.0D0
        !            74:       IF (N.LE.0) RETURN
        !            75:       IF (INCX.EQ.INCY .AND. INCX.GT.0) GO TO 20
        !            76: *
        !            77: *     Code for unequal or nonpositive increments.
        !            78: *
        !            79:       KX = 1
        !            80:       KY = 1
        !            81:       IF (INCX.LT.0) KX = 1 + (1-N)*INCX
        !            82:       IF (INCY.LT.0) KY = 1 + (1-N)*INCY
        !            83:       DO 10 I = 1,N
        !            84:           DSDOT = DSDOT + DBLE(SX(KX))*DBLE(SY(KY))
        !            85:           KX = KX + INCX
        !            86:           KY = KY + INCY
        !            87:    10 CONTINUE
        !            88:       RETURN
        !            89: *
        !            90: *     Code for equal, positive, non-unit increments.
        !            91: *
        !            92:    20 NS = N*INCX
        !            93:       DO 30 I = 1,NS,INCX
        !            94:           DSDOT = DSDOT + DBLE(SX(I))*DBLE(SY(I))
        !            95:    30 CONTINUE
        !            96:       RETURN
        !            97:       END