/[ascend]/trunk/blas/daxpy.f
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Contents of /trunk/blas/daxpy.f

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Fri Oct 29 20:54:12 2004 UTC (15 years, 8 months ago) by aw0a
File size: 1358 byte(s)
Setting up web subdirectory in repository
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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