Keeping Lanczos would be nice, Like I said, it's currently being used in some projects with good results and I think it's easier to tune so it would be my first choice for future developments. I still need to further test SSVD, specially because in the current example I'm working it yields very different results from Lanczos. We are investigating if it can be due to a bug when loading the data, though dimensions of the ouptut seem ok, or if it's a question of increasing p or q parameters. If it's a question of increasing p and q I think running times would make SSVD not viable. I hope to be able to provide some comparison figures in terms of precision and running time in a month or so.
I hope that other users reads this and say wether they are using Lanczos. Best, Fernando. 2013/8/2 Sebastian Schelter <[email protected]> > I would also be fine with keeping if there is demand. I just proposed to > deprecate it and nobody voted against that at that point in time. > > --sebastian > > > On 02.08.2013 03:12, Dmitriy Lyubimov wrote: > > There's a part of Nathan Halko's dissertation referenced on algorithm > page > > running comparison. In particular, he was not able to compute more than > 40 > > eigenvectors with Lanczos on wikipedia dataset. You may refer to that > > study. > > > > On the accuracy part, it was not observed that it was a problem, assuming > > high level of random noise is not the case, at least not in LSA-like > > application used there. > > > > That said, i am all for diversity of tools, I would actually be +0 on > > deprecating Lanczos, it is not like we are lacking support for it. SSVD > > could use improvements too. > > > > > > On Thu, Aug 1, 2013 at 3:15 AM, Fernando Fernández < > > [email protected]> wrote: > > > >> Hi everyone, > >> > >> Sorry if I duplicate the question but I've been looking for an answer > and I > >> haven't found an explanation other than it's not being used (together > with > >> some other algorithms). If it's been discussed in depth before maybe you > >> can point me to some link with the discussion. > >> > >> I have successfully used Lanczos in several projects and it's been a > >> surprise to me finding that the main reason (according to what I've read > >> that might not be the full story) is that it's not being used. At the > >> begining I supposed it was because SSVD is supposed to be much faster > with > >> similar results, but after making some tests I have found that running > >> times are similar or even worse than lanczos for some configurations (I > >> have tried several combinations of parameters, given child processes > enough > >> memory, etc. and had no success in running SSVD at least in 3/4 of time > >> Lanczos runs, thouh they might be some combinations of parameters I have > >> still not tried). It seems to be quite tricky to find a good > combination of > >> parameters for SSVD and I have seen also a precision loss in some > examples > >> that makes me not confident in migrating Lanczos to SSVD from now on > (How > >> far can I trust results from a combination of parameters that runs in > >> significant less time, or at least a good time?). > >> > >> Can someone convince me that SSVD is actually a better option than > Lanczos? > >> (I'm totally willing to be convinced... :) ) > >> > >> Thank you very much in advance. > >> > >> Fernando. > >> > > > >
