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
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