mysaxpy Subroutine

      subroutine mysaxpy(a,x,y,n)
      implicit double precision (a-h,o-z)
      dimension x(*),y(*)
      if (a==0.D0) return
      do i=1,n
        y(i)=y(i)+a*x(i)
      end do
      end subroutine mysaxpy