/[ascend]/trunk/blas/ddot.f
ViewVC logotype

Contents of /trunk/blas/ddot.f

Parent Directory Parent Directory | Revision Log Revision Log


Revision 1 - (show annotations) (download)
Fri Oct 29 20:54:12 2004 UTC (15 years, 5 months ago) by aw0a
File size: 1388 byte(s)
Setting up web subdirectory in repository
1 C ddot.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 double precision function ddot(n,dx,incx,dy,incy)
7 c
8 c forms the dot product of two vectors.
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(*),dtemp
13 integer i,incx,incy,ix,iy,m,mp1,n
14 c
15 ddot = 0.0d0
16 dtemp = 0.0d0
17 if(n.le.0)return
18 if(incx.eq.1.and.incy.eq.1)go to 20
19 c
20 c code for unequal increments or equal increments
21 c not equal to 1
22 c
23 ix = 1
24 iy = 1
25 if(incx.lt.0)ix = (-n+1)*incx + 1
26 if(incy.lt.0)iy = (-n+1)*incy + 1
27 do 10 i = 1,n
28 dtemp = dtemp + dx(ix)*dy(iy)
29 ix = ix + incx
30 iy = iy + incy
31 10 continue
32 ddot = dtemp
33 return
34 c
35 c code for both increments equal to 1
36 c
37 c
38 c clean-up loop
39 c
40 20 m = mod(n,5)
41 if( m .eq. 0 ) go to 40
42 do 30 i = 1,m
43 dtemp = dtemp + dx(i)*dy(i)
44 30 continue
45 if( n .lt. 5 ) go to 60
46 40 mp1 = m + 1
47 do 50 i = mp1,n,5
48 dtemp = dtemp + dx(i)*dy(i) + dx(i + 1)*dy(i + 1) +
49 * dx(i + 2)*dy(i + 2) + dx(i + 3)*dy(i + 3) + dx(i + 4)*dy(i + 4)
50 50 continue
51 60 ddot = dtemp
52 return
53 end
54
55

john.pye@anu.edu.au
ViewVC Help
Powered by ViewVC 1.1.22