mlosch/optim_m1qn3/ddot.F

      double precision function ddot(n,dx,incx,dy,incy)
c
c     forms the dot product of two vectors.
c     uses unrolled loops for increments equal to one.
c     jack dongarra, linpack, 3/11/78.
c     modified 12/3/93, array(1) declarations changed to array(*)
c
      double precision dx(*),dy(*),dtemp
      integer i,incx,incy,ix,iy,m,mp1,n
c
      ddot = 0.0d0
      dtemp = 0.0d0
      if(n.le.0)return
      if(incx.eq.1.and.incy.eq.1)go to 20
c
c        code for unequal increments or equal increments
c          not equal to 1
c
      ix = 1
      iy = 1
      if(incx.lt.0)ix = (-n+1)*incx + 1
      if(incy.lt.0)iy = (-n+1)*incy + 1
      do 10 i = 1,n
        dtemp = dtemp + dx(ix)*dy(iy)
        ix = ix + incx
        iy = iy + incy
   10 continue
      ddot = dtemp
      return
c
c        code for both increments equal to 1
c
c
c        clean-up loop
c
   20 m = mod(n,5)
      if( m .eq. 0 ) go to 40
      do 30 i = 1,m
        dtemp = dtemp + dx(i)*dy(i)
   30 continue
      if( n .lt. 5 ) go to 60
   40 mp1 = m + 1
      do 50 i = mp1,n,5
        dtemp = dtemp + dx(i)*dy(i) + dx(i + 1)*dy(i + 1) +
     *   dx(i + 2)*dy(i + 2) + dx(i + 3)*dy(i + 3) + dx(i + 4)*dy(i + 4)
   50 continue
   60 ddot = dtemp
      return
      end
1	double precision function ddot(n,dx,incx,dy,incy)
2	c
3	c forms the dot product of two vectors.
4	c uses unrolled loops for increments equal to one.
5	c jack dongarra, linpack, 3/11/78.
6	c modified 12/3/93, array(1) declarations changed to array(*)
7	c
8	double precision dx(),dy(),dtemp
9	integer i,incx,incy,ix,iy,m,mp1,n
10	c
11	ddot = 0.0d0
12	dtemp = 0.0d0
13	if(n.le.0)return
14	if(incx.eq.1.and.incy.eq.1)go to 20
15	c
16	c code for unequal increments or equal increments
17	c not equal to 1
18	c
19	ix = 1
20	iy = 1
21	if(incx.lt.0)ix = (-n+1)*incx + 1
22	if(incy.lt.0)iy = (-n+1)*incy + 1
23	do 10 i = 1,n
24	dtemp = dtemp + dx(ix)*dy(iy)
25	ix = ix + incx
26	iy = iy + incy
27	10 continue
28	ddot = dtemp
29	return
30	c
31	c code for both increments equal to 1
32	c
33	c
34	c clean-up loop
35	c
36	20 m = mod(n,5)
37	if( m .eq. 0 ) go to 40
38	do 30 i = 1,m
39	dtemp = dtemp + dx(i)*dy(i)
40	30 continue
41	if( n .lt. 5 ) go to 60
42	40 mp1 = m + 1
43	do 50 i = mp1,n,5
44	dtemp = dtemp + dx(i)dy(i) + dx(i + 1)dy(i + 1) +
45	* dx(i + 2)dy(i + 2) + dx(i + 3)dy(i + 3) + dx(i + 4)*dy(i + 4)
46	50 continue
47	60 ddot = dtemp
48	return
49	end