stdlib_sscal Subroutine

public pure subroutine stdlib_sscal(n, sa, sx, incx)

SSCAL scales a vector by a constant. uses unrolled loops for increment equal to 1.

Arguments

Type IntentOptional Attributes Name
integer(kind=ilp), intent(in) :: n
real(kind=sp), intent(in) :: sa
real(kind=sp), intent(inout) :: sx(*)
integer(kind=ilp), intent(in) :: incx

Source Code

     pure subroutine stdlib_sscal(n,sa,sx,incx)
     !! SSCAL scales a vector by a constant.
     !! uses unrolled loops for increment equal to 1.
        ! -- reference blas level1 routine --
        ! -- reference blas is a software package provided by univ. of tennessee,    --
        ! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
           ! Scalar Arguments 
           real(sp), intent(in) :: sa
           integer(ilp), intent(in) :: incx, n
           ! Array Arguments 
           real(sp), intent(inout) :: sx(*)
        ! =====================================================================
           ! Local Scalars 
           integer(ilp) :: i, m, mp1, nincx
           ! Intrinsic Functions 
           intrinsic :: mod
           if (n<=0 .or. incx<=0) return
           if (incx==1) then
              ! code for increment equal to 1
              ! clean-up loop
              m = mod(n,5)
              if (m/=0) then
                 do i = 1,m
                    sx(i) = sa*sx(i)
                 end do
                 if (n<5) return
              end if
              mp1 = m + 1
              do 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)
              end do
           else
              ! code for increment not equal to 1
              nincx = n*incx
              do i = 1,nincx,incx
                 sx(i) = sa*sx(i)
              end do
           end if
           return
     end subroutine stdlib_sscal