parallel computing – Multi-threaded algorithm

// scalar product for the n-length vector
function d = par-dot-prod (x, y)
if length (x) = 1 then
back x.y
end if
split x = [Xl Xr] and y = [Yl Yr]
   spawn dl = par-dot-prod (xl, yl)
spawn dr = by-dot-prod (xr, yr)
synchronize
return dl + dr
final function 

I wrote the part of the problem related to the dot product. But now, I do not know how to use it to solve the matrix multiplication with the Big-Oh works (n ^ 3) and the reach of Big-Oh (logn).

We are dealing with a multithreaded algorithm here.