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
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