Wow, seems like I have started a nice discussion here... Thanks a lot for your ideas, very helpful!!
2011/12/12 Dmitriy Lyubimov <[email protected]> > 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. > >> >
