another idea i have re: 922 is to perform computation of AB' blocks using single precision arithmetic. as far as i understand, rounding errors are not very essential there as we are just trying to improve our initially completely random basis.
On Mon, Dec 12, 2011 at 11:53 AM, Ted Dunning <[email protected]> wrote: > Also, it isn't entirely clear yet whether power iterations are more > efficient than simply increasing the fudge factor p. Power iterations are > very effective, and increasing p increases costs in the cube, but running > MR passes is expensive enough that some increase in p might be sufficient > and still faster than a power iteration. > > On Mon, Dec 12, 2011 at 12:48 PM, Dmitriy Lyubimov <[email protected]>wrote: > >> With power iterations it is + 2 more for each new power iteration. >> Power iterations seem to be expensive in cases when A is very sparse >> (size of (A) ~= size of (B) then power iteration essentially is >> equivalent to computing AA' although i believe i manage to do it a >> little bit more efficient here with MAHOUT-922 then >> DRM.timesSquaired(A) would do). >> >> If A is dense, then power iterations make much more sense and not that >> expensive. >>
