Did that. You are right. The QRD in mahout is abysmally slow. I wrote a new version on the airplane that seems to be about 10x faster and still jsut about as accurate (and vastly simpler). I will put up some tests and a patch in the next week or so.
On Thu, Jan 24, 2013 at 4:55 PM, Ted Dunning <[email protected]> wrote: > Hmph. That suggests to me that I need to rewrite our QRDecomposition. > > > On Thu, Jan 24, 2013 at 8:27 AM, Ying Liao <[email protected]> wrote: > >> Sean suggests "replacing this with a call to the Apache Commons Math >> QRDecomposition" and the sloving time is reduced significantly. Thanks. >> >> >> On Wed, Jan 23, 2013 at 5:10 PM, Ted Dunning <[email protected]> >> wrote: >> >> > That is a long time for such a small qr decomposition. I wouldn't think >> > that the actually solving would add that much time, either. >> > >> > On Thu, Jan 24, 2013 at 2:00 AM, Ying Liao <[email protected]> wrote: >> > >> > > Hi! >> > > The QRDecomposition turns out to be my bottleneck in deploying >> ALS-WR. It >> > > takes less than a ms to solve X=A^{-1}B when A is 20*20. But it takes >> > 55ms >> > > per solve when A is 60*60. Is there a different approach to solve >> AX=B? >> > > >> > > Thanks, >> > > Ying >> > > >> > >> > >
