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    1:       SUBROUTINE DSCAL(N,DA,DX,INCX)
    2: *     .. Scalar Arguments ..
    3:       DOUBLE PRECISION DA
    4:       INTEGER INCX,N
    5: *     ..
    6: *     .. Array Arguments ..
    7:       DOUBLE PRECISION DX(*)
    8: *     ..
    9: *
   10: *  Purpose
   11: *  =======
   12: *
   13: *     DSCAL scales a vector by a constant.
   14: *     uses unrolled loops for increment equal to one.
   15: *
   16: *  Further Details
   17: *  ===============
   18: *
   19: *     jack dongarra, linpack, 3/11/78.
   20: *     modified 3/93 to return if incx .le. 0.
   21: *     modified 12/3/93, array(1) declarations changed to array(*)
   22: *
   23: *  =====================================================================
   24: *
   25: *     .. Local Scalars ..
   26:       INTEGER I,M,MP1,NINCX
   27: *     ..
   28: *     .. Intrinsic Functions ..
   29:       INTRINSIC MOD
   30: *     ..
   31:       IF (N.LE.0 .OR. INCX.LE.0) RETURN
   32:       IF (INCX.EQ.1) THEN
   33: *
   34: *        code for increment equal to 1
   35: *
   36: *
   37: *        clean-up loop
   38: *
   39:          M = MOD(N,5)
   40:          IF (M.NE.0) THEN
   41:             DO I = 1,M
   42:                DX(I) = DA*DX(I)
   43:             END DO
   44:             IF (N.LT.5) RETURN
   45:          END IF
   46:          MP1 = M + 1
   47:          DO I = MP1,N,5
   48:             DX(I) = DA*DX(I)
   49:             DX(I+1) = DA*DX(I+1)
   50:             DX(I+2) = DA*DX(I+2)
   51:             DX(I+3) = DA*DX(I+3)
   52:             DX(I+4) = DA*DX(I+4)
   53:          END DO
   54:       ELSE
   55: *
   56: *        code for increment not equal to 1
   57: *
   58:          NINCX = N*INCX
   59:          DO I = 1,NINCX,INCX
   60:             DX(I) = DA*DX(I)
   61:          END DO
   62:       END IF
   63:       RETURN
   64:       END