```01:       SUBROUTINE DCOPY(N,DX,INCX,DY,INCY)
02: *     .. Scalar Arguments ..
03:       INTEGER INCX,INCY,N
04: *     ..
05: *     .. Array Arguments ..
06:       DOUBLE PRECISION DX(*),DY(*)
07: *     ..
08: *
09: *  Purpose
10: *  =======
11: *
12: *     copies a vector, x, to a vector, y.
13: *     uses unrolled loops for increments equal to one.
14: *     jack dongarra, linpack, 3/11/78.
15: *     modified 12/3/93, array(1) declarations changed to array(*)
16: *
17: *
18: *     .. Local Scalars ..
19:       INTEGER I,IX,IY,M,MP1
20: *     ..
21: *     .. Intrinsic Functions ..
22:       INTRINSIC MOD
23: *     ..
24:       IF (N.LE.0) RETURN
25:       IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
26: *
27: *        code for unequal increments or equal increments
28: *          not equal to 1
29: *
30:       IX = 1
31:       IY = 1
32:       IF (INCX.LT.0) IX = (-N+1)*INCX + 1
33:       IF (INCY.LT.0) IY = (-N+1)*INCY + 1
34:       DO 10 I = 1,N
35:           DY(IY) = DX(IX)
36:           IX = IX + INCX
37:           IY = IY + INCY
38:    10 CONTINUE
39:       RETURN
40: *
41: *        code for both increments equal to 1
42: *
43: *
44: *        clean-up loop
45: *
46:    20 M = MOD(N,7)
47:       IF (M.EQ.0) GO TO 40
48:       DO 30 I = 1,M
49:           DY(I) = DX(I)
50:    30 CONTINUE
51:       IF (N.LT.7) RETURN
52:    40 MP1 = M + 1
53:       DO 50 I = MP1,N,7
54:           DY(I) = DX(I)
55:           DY(I+1) = DX(I+1)
56:           DY(I+2) = DX(I+2)
57:           DY(I+3) = DX(I+3)
58:           DY(I+4) = DX(I+4)
59:           DY(I+5) = DX(I+5)
60:           DY(I+6) = DX(I+6)
61:    50 CONTINUE
62:       RETURN
63:       END
64: ```