subroutine sscal (n, sa, sx, incx)
C***BEGIN PROLOGUE  SSCAL
C***PURPOSE  Multiply a vector by a constant.
C***CATEGORY  D1A6
C***TYPE      SINGLE PRECISION (SSCAL-S, DSCAL-D, CSCAL-C)
C***KEYWORDS  BLAS, LINEAR ALGEBRA, SCALE, 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       SA  single precision scale factor
C       SX  single precision vector with N elements
C     INCX  storage spacing between elements of SX
C
C     --Output--
C       SX  single precision result (unchanged if N .LE. 0)
C
C     Replace single precision SX by single precision SA*SX.
C     For I = 0 to N-1, replace SX(IX+I*INCX) with  SA * SX(IX+I*INCX),
C     where IX = 1 if INCX .GE. 0, else IX = 1+(1-N)*INCX.
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   900821  Modified to correct problem with a negative increment.
C           (WRB)
C   920501  Reformatted the REFERENCES section.  (WRB)
C***END PROLOGUE  SSCAL
      real sa, sx(*)
      integer i, incx, ix, m, mp1, n
c***first executable statement  sscal
      if (n .le. 0) return
      if (incx .eq. 1) goto 20
c
c     code for increment not equal to 1.
c
      ix = 1
      if (incx .lt. 0) ix = (-n+1)*incx + 1
      do 10 i = 1,n
        sx(ix) = sa*sx(ix)
        ix = ix + incx
   10 continue
      return
c
c     code for increment 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) goto 40
      do 30 i = 1,m
        sx(i) = sa*sx(i)
   30 continue
      if (n .lt. 5) return
   40 mp1 = m + 1
      do 50 i = mp1,n,5
        sx(i) = sa*sx(i)
        sx(i+1) = sa*sx(i+1)
        sx(i+2) = sa*sx(i+2)
        sx(i+3) = sa*sx(i+3)
        sx(i+4) = sa*sx(i+4)
   50 continue
      return
      end