/[ascend]/trunk/blas/daxpy.f
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Fri Oct 29 20:54:12 2004 UTC (15 years, 7 months ago) by aw0a
File size: 1358 byte(s)
Setting up web subdirectory in repository
1 aw0a 1 C daxpy.f
2     C is freely available from netlib. It is not subject to any GNU License
3     C set by the authors of the ASCEND math programming system.
4     C $Date: 1996/04/30 18:14:07 $ $Revision: 1.1.1.1 $
5     C
6     subroutine daxpy(n,da,dx,incx,dy,incy)
7     c
8     c constant times a vector plus a vector.
9     c uses unrolled loops for increments equal to one.
10     c jack dongarra, linpack, 3/11/78.
11     c
12     double precision dx(*),dy(*),da
13     integer i,incx,incy,ix,iy,m,mp1,n
14     c
15     if(n.le.0)return
16     if (da .eq. 0.0d0) return
17     if(incx.eq.1.and.incy.eq.1)go to 20
18     c
19     c code for unequal increments or equal increments
20     c not equal to 1
21     c
22     ix = 1
23     iy = 1
24     if(incx.lt.0)ix = (-n+1)*incx + 1
25     if(incy.lt.0)iy = (-n+1)*incy + 1
26     do 10 i = 1,n
27     dy(iy) = dy(iy) + da*dx(ix)
28     ix = ix + incx
29     iy = iy + incy
30     10 continue
31     return
32     c
33     c code for both increments equal to 1
34     c
35     c
36     c clean-up loop
37     c
38     20 m = mod(n,4)
39     if( m .eq. 0 ) go to 40
40     do 30 i = 1,m
41     dy(i) = dy(i) + da*dx(i)
42     30 continue
43     if( n .lt. 4 ) return
44     40 mp1 = m + 1
45     do 50 i = mp1,n,4
46     dy(i) = dy(i) + da*dx(i)
47     dy(i + 1) = dy(i + 1) + da*dx(i + 1)
48     dy(i + 2) = dy(i + 2) + da*dx(i + 2)
49     dy(i + 3) = dy(i + 3) + da*dx(i + 3)
50     50 continue
51     return
52     end
53    

john.pye@anu.edu.au
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