Return to dscal.f CVS log

Up to [local] / rpl / lapack / blas

Initial revision

    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) GO TO 20
   33: *
   34: *        code for increment not equal to 1
   35: *
   36:       NINCX = N*INCX
   37:       DO 10 I = 1,NINCX,INCX
   38:           DX(I) = DA*DX(I)
   39:    10 CONTINUE
   40:       RETURN
   41: *
   42: *        code for increment equal to 1
   43: *
   44: *
   45: *        clean-up loop
   46: *
   47:    20 M = MOD(N,5)
   48:       IF (M.EQ.0) GO TO 40
   49:       DO 30 I = 1,M
   50:           DX(I) = DA*DX(I)
   51:    30 CONTINUE
   52:       IF (N.LT.5) RETURN
   53:    40 MP1 = M + 1
   54:       DO 50 I = MP1,N,5
   55:           DX(I) = DA*DX(I)
   56:           DX(I+1) = DA*DX(I+1)
   57:           DX(I+2) = DA*DX(I+2)
   58:           DX(I+3) = DA*DX(I+3)
   59:           DX(I+4) = DA*DX(I+4)
   60:    50 CONTINUE
   61:       RETURN
   62:       END