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Contents of /trunk/blas/dswap.f

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Revision 1 - (show annotations) (download)
Fri Oct 29 20:54:12 2004 UTC (15 years, 3 months ago) by aw0a
File size: 1117 byte(s)
Setting up web subdirectory in repository
1 SUBROUTINE DSWAP (N,DX,INCX,DY,INCY)
2 C
3 C INTERCHANGES TWO VECTORS.
4 C USES UNROLLED LOOPS FOR INCREMENTS EQUAL ONE.
5 C JACK DONGARRA, LINPACK, 3/11/78.
6 C
7 DOUBLE PRECISION DX(*),DY(*),DTEMP
8 INTEGER I,INCX,INCY,IX,IY,M,MP1,N
9 C
10 IF(N.LE.0)RETURN
11 IF(INCX.EQ.1.AND.INCY.EQ.1)GO TO 20
12 C
13 C CODE FOR UNEQUAL INCREMENTS OR EQUAL INCREMENTS NOT EQUAL
14 C TO 1
15 C
16 IX = 1
17 IY = 1
18 IF(INCX.LT.0)IX = (-N+1)*INCX + 1
19 IF(INCY.LT.0)IY = (-N+1)*INCY + 1
20 DO 10 I = 1,N
21 DTEMP = DX(IX)
22 DX(IX) = DY(IY)
23 DY(IY) = DTEMP
24 IX = IX + INCX
25 IY = IY + INCY
26 10 CONTINUE
27 RETURN
28 C
29 C CODE FOR BOTH INCREMENTS EQUAL TO 1
30 C
31 C
32 C CLEAN-UP LOOP
33 C
34 20 M = MOD(N,3)
35 IF( M .EQ. 0 ) GO TO 40
36 DO 30 I = 1,M
37 DTEMP = DX(I)
38 DX(I) = DY(I)
39 DY(I) = DTEMP
40 30 CONTINUE
41 IF( N .LT. 3 ) RETURN
42 40 MP1 = M + 1
43 DO 50 I = MP1,N,3
44 DTEMP = DX(I)
45 DX(I) = DY(I)
46 DY(I) = DTEMP
47 DTEMP = DX(I + 1)
48 DX(I + 1) = DY(I + 1)
49 DY(I + 1) = DTEMP
50 DTEMP = DX(I + 2)
51 DX(I + 2) = DY(I + 2)
52 DY(I + 2) = DTEMP
53 50 CONTINUE
54 RETURN
55 END

john.pye@anu.edu.au
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