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	mlosch	1.1	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