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SUBROUTINE DSCAL(N,DA,DX,INCX)
* .. Scalar Arguments ..
DOUBLE PRECISION DA
INTEGER INCX,N
* ..
* .. Array Arguments ..
DOUBLE PRECISION DX(*)
* ..
*
* Purpose
* =======
*
* DSCAL scales a vector by a constant.
* uses unrolled loops for increment equal to one.
*
* 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(*)
*
* =====================================================================
*
* .. Local Scalars ..
INTEGER I,M,MP1,NINCX
* ..
* .. Intrinsic Functions ..
INTRINSIC MOD
* ..
IF (N.LE.0 .OR. INCX.LE.0) RETURN
IF (INCX.EQ.1) GO TO 20
*
* code for increment not equal to 1
*
NINCX = N*INCX
DO 10 I = 1,NINCX,INCX
DX(I) = DA*DX(I)
10 CONTINUE
RETURN
*
* code for increment equal to 1
*
*
* clean-up loop
*
20 M = MOD(N,5)
IF (M.EQ.0) GO TO 40
DO 30 I = 1,M
DX(I) = DA*DX(I)
30 CONTINUE
IF (N.LT.5) RETURN
40 MP1 = M + 1
DO 50 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)
50 CONTINUE
RETURN
END
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