real function sdot (n, sx, incx, sy, incy)
C***BEGIN PROLOGUE  SDOT
C***PURPOSE  Compute the inner product of two vectors.
C***CATEGORY  D1A4
C***TYPE      SINGLE PRECISION (SDOT-S, DDOT-D, CDOTU-C)
C***KEYWORDS  BLAS, 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       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     sdot  single precision dot product (zero if n .le. 0)
C
C     Returns the dot product of single precision SX and SY.
C     SDOT = 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   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   010807  Added specific declaration for all variables (FAF)
C***END PROLOGUE  SDOT
      real sx(*), sy(*)
      integer incy, incx, n, ix, iy, i, m, mp1, ns
c***first executable statement  sdot
      sdot = 0.0e0
      if (n .le. 0) return
      if (incx .eq. incy) if (incx-1) 5,20,60
c
c     code for unequal or nonpositive increments.
c
    5 ix = 1
      iy = 1
      if (incx .lt. 0) ix = (-n+1)*incx + 1
      if (incy .lt. 0) iy = (-n+1)*incy + 1
      do 10 i = 1,n
        sdot = sdot + sx(ix)*sy(iy)
        ix = ix + incx
        iy = iy + incy
   10 continue
      return
c
c     code for both increments equal to 1.
c
c     clean-up loop so remaining vector length is a multiple of 5.
c
   20 m = mod(n,5)
      if (m .eq. 0) go to 40
      do 30 i = 1,m
        sdot = sdot + sx(i)*sy(i)
   30 continue
      if (n .lt. 5) return
   40 mp1 = m + 1
      do 50 i = mp1,n,5
      sdot = sdot + sx(i)*sy(i) + sx(i+1)*sy(i+1) + sx(i+2)*sy(i+2) +
     1              sx(i+3)*sy(i+3) + sx(i+4)*sy(i+4)
   50 continue
      return
c
c     code for equal, positive, non-unit increments.
c
   60 ns = n*incx
      do 70 i = 1,ns,incx
        sdot = sdot + sx(i)*sy(i)
   70 continue
      return
      end