-Re: Mahout LanczosSolver explanation
Ted Dunning 2012-08-01, 01:34
Stochastic SVD and alternating least squares would both be better, I think.
On Tue, Jul 31, 2012 at 7:28 PM, Aniruddha Basak <[EMAIL PROTECTED]>wrote:
> I did not choose Lanczos. It found it being used as a part of
> implemented in Mahout.
> Can u please recommend some better alternative of Lanczos.
> -----Original Message-----
> From: Ted Dunning [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, July 31, 2012 6:24 PM
> To: [EMAIL PROTECTED]
> Cc: Jake Mannix
> Subject: Re: Mahout LanczosSolver explanation
> WHy are you using Lanczos? Why not use something more recent?
> On Tue, Jul 31, 2012 at 7:00 PM, Aniruddha Basak <[EMAIL PROTECTED]
> > Hi,
> > I am working on Spectral Kmeans which involves an eigen-decomposition
> > step using Lanczos. As I did not get exact similar results as
> > expected, I tried to understand the implementation.
> > I have one question about "LanczosSolver .java" :
> > In the "solve" method, while building the "tridiagonal matrix" there
> > is a step just after the multiplication job (performed on Hadoop as
> > TimesSquaredJob) as
> > ------------
> > nextVector.assign(new Scale(1.0 / state.getScaleFactor()));
> > -----------
> > I could not understand why this scaling is performed?
> > ( When I compared the results on a small matrix to an equivalent
> > Matlab script, I found the results are exactly similar WITHOUT this
> > scaling. Including this scaling makes the results different from the
> > Matlab results. )
> > Thanks,
> > Aniruddha