real function sdotf(n,sx,incx,sy,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 real sx(*),sy(*),stemp integer i,incx,incy,ix,iy,m,mp1,n c stemp = 0.0e0 sdotf = 0.0e0 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 stemp = stemp + sx(ix)*sy(iy) ix = ix + incx iy = iy + incy 10 continue sdotf = stemp 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 stemp = stemp + sx(i)*sy(i) 30 continue if( n .lt. 5 ) go to 60 40 mp1 = m + 1 do 50 i = mp1,n,5 stemp = stemp + sx(i)*sy(i) + sx(i + 1)*sy(i + 1) + * sx(i + 2)*sy(i + 2) + sx(i + 3)*sy(i + 3) + sx(i + 4)*sy(i + 4) 50 continue 60 sdotf = stemp return end