dscal()

subroutine dscal	(	integer	n,
		double precision	da,
		double precision, dimension(*)	dx,
		integer	incx
	)

DSCAL

Purpose:

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

Parameters

[in]	N	N is INTEGER number of elements in input vector(s)
[in]	DA	DA is DOUBLE PRECISION On entry, DA specifies the scalar alpha.
[in,out]	DX	DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
[in]	INCX	INCX is INTEGER storage spacing between elements of DX

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Further Details:

     jack dongarra, linpack, 3/11/78.
     modified 3/93 to return if incx .le. 0.
     modified 12/3/93, array(1) declarations changed to array(*)

Definition at line 78 of file dscal.f.

*
*  -- 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 ..
      DOUBLE PRECISION DA
      INTEGER INCX,N
*     ..
*     .. Array Arguments ..
      DOUBLE PRECISION DX(*)
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      INTEGER I,M,MP1,NINCX
*     .. Parameters ..
      DOUBLE PRECISION ONE
      parameter(one=1.0d+0)
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC mod
*     ..
      IF (n.LE.0 .OR. incx.LE.0 .OR. da.EQ.one) RETURN
      IF (incx.EQ.1) THEN
*
*        code for increment equal to 1
*
*
*        clean-up loop
*
         m = mod(n,5)
         IF (m.NE.0) THEN
            DO i = 1,m
               dx(i) = da*dx(i)
            END DO
            IF (n.LT.5) RETURN
         END IF
         mp1 = m + 1
         DO i = mp1,n,5
            dx(i) = da*dx(i)
            dx(i+1) = da*dx(i+1)
            dx(i+2) = da*dx(i+2)
            dx(i+3) = da*dx(i+3)
            dx(i+4) = da*dx(i+4)
         END DO
      ELSE
*
*        code for increment not equal to 1
*
         nincx = n*incx
         DO i = 1,nincx,incx
            dx(i) = da*dx(i)
         END DO
      END IF
      RETURN
*
*     End of DSCAL
*