1 SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY)
2 * .. Scalar Arguments ..
3 DOUBLE PRECISION DA
4 INTEGER INCX,INCY,N
5 * ..
6 * .. Array Arguments ..
7 DOUBLE PRECISION DX(*),DY(*)
8 * ..
9 *
10 * Purpose
11 * =======
12 *
13 * DAXPY constant times a vector plus a vector.
14 * uses unrolled loops for increments equal to one.
15 *
16 * Further Details
17 * ===============
18 *
19 * jack dongarra, linpack, 3/11/78.
20 * modified 12/3/93, array(1) declarations changed to array(*)
21 *
22 * =====================================================================
23 *
24 * .. Local Scalars ..
25 INTEGER I,IX,IY,M,MP1
26 * ..
27 * .. Intrinsic Functions ..
28 INTRINSIC MOD
29 * ..
30 IF (N.LE.0) RETURN
31 IF (DA.EQ.0.0d0) RETURN
32 IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
33 *
34 * code for both increments equal to 1
35 *
36 *
37 * clean-up loop
38 *
39 M = MOD(N,4)
40 IF (M.NE.0) THEN
41 DO I = 1,M
42 DY(I) = DY(I) + DA*DX(I)
43 END DO
44 END IF
45 IF (N.LT.4) RETURN
46 MP1 = M + 1
47 DO I = MP1,N,4
48 DY(I) = DY(I) + DA*DX(I)
49 DY(I+1) = DY(I+1) + DA*DX(I+1)
50 DY(I+2) = DY(I+2) + DA*DX(I+2)
51 DY(I+3) = DY(I+3) + DA*DX(I+3)
52 END DO
53 ELSE
54 *
55 * code for unequal increments or equal increments
56 * not equal to 1
57 *
58 IX = 1
59 IY = 1
60 IF (INCX.LT.0) IX = (-N+1)*INCX + 1
61 IF (INCY.LT.0) IY = (-N+1)*INCY + 1
62 DO I = 1,N
63 DY(IY) = DY(IY) + DA*DX(IX)
64 IX = IX + INCX
65 IY = IY + INCY
66 END DO
67 END IF
68 RETURN
69 END
2 * .. Scalar Arguments ..
3 DOUBLE PRECISION DA
4 INTEGER INCX,INCY,N
5 * ..
6 * .. Array Arguments ..
7 DOUBLE PRECISION DX(*),DY(*)
8 * ..
9 *
10 * Purpose
11 * =======
12 *
13 * DAXPY constant times a vector plus a vector.
14 * uses unrolled loops for increments equal to one.
15 *
16 * Further Details
17 * ===============
18 *
19 * jack dongarra, linpack, 3/11/78.
20 * modified 12/3/93, array(1) declarations changed to array(*)
21 *
22 * =====================================================================
23 *
24 * .. Local Scalars ..
25 INTEGER I,IX,IY,M,MP1
26 * ..
27 * .. Intrinsic Functions ..
28 INTRINSIC MOD
29 * ..
30 IF (N.LE.0) RETURN
31 IF (DA.EQ.0.0d0) RETURN
32 IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
33 *
34 * code for both increments equal to 1
35 *
36 *
37 * clean-up loop
38 *
39 M = MOD(N,4)
40 IF (M.NE.0) THEN
41 DO I = 1,M
42 DY(I) = DY(I) + DA*DX(I)
43 END DO
44 END IF
45 IF (N.LT.4) RETURN
46 MP1 = M + 1
47 DO I = MP1,N,4
48 DY(I) = DY(I) + DA*DX(I)
49 DY(I+1) = DY(I+1) + DA*DX(I+1)
50 DY(I+2) = DY(I+2) + DA*DX(I+2)
51 DY(I+3) = DY(I+3) + DA*DX(I+3)
52 END DO
53 ELSE
54 *
55 * code for unequal increments or equal increments
56 * not equal to 1
57 *
58 IX = 1
59 IY = 1
60 IF (INCX.LT.0) IX = (-N+1)*INCX + 1
61 IF (INCY.LT.0) IY = (-N+1)*INCY + 1
62 DO I = 1,N
63 DY(IY) = DY(IY) + DA*DX(IX)
64 IX = IX + INCX
65 IY = IY + INCY
66 END DO
67 END IF
68 RETURN
69 END