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From: PEDRO MANUEL JIMENEZ RODRIGUEZ <pmjimenez1983@hotmail.com>
To: <user@mahout.apache.org>
Subject: RE: Lanczos Algorithm
Date: Wed, 24 Nov 2010 20:33:39 +0100
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Hi Ted=2C

This is in the worst case. I=A0 haved asked for the amount of data and that=
's what somebody told me. Anyway I'm not going to make any test with that a=
mount of data.=20

I'm doing my final year project and I just have to make this works with a r=
easonable amount of data. So I just need to know how the algorithm it's wor=
king and why I'm getting different values when I compare the results with a=
nother implementation in R.

=A0
=A0

----------------------------------------
> From: ted.dunning@gmail.com
> Date: Tue=2C 23 Nov 2010 14:55:00 -0800
> Subject: Re: Lanczos Algorithm
> To: user@mahout.apache.org
>
> I seriously doubt that=2C actually. 10^14 is a very large number.
>
> As far as I know=2C the record for computing an SVD of a large sparse mat=
rix
> started with about 2-3 x 10^9 non-zero elements. You are saying that your
> problem is 100=2C000 times larger than this. I think that you are going t=
o
> have to
> wait for another 15 compute speed doubling times before this becomes a
> feasible computation.
>
> On Tue=2C Nov 23=2C 2010 at 11:55 AM=2C PEDRO MANUEL JIMENEZ RODRIGUEZ <
> pmjimenez1983@hotmail.com> wrote:
>
> > Well=2C this is in the worst case but it could be possible.
> >
> > I'm not going to make any tests with this amount of data because for me=
 is
> > impossible but this project is part of a bigger one and they would have
> > enough space to deal with this amount of data.
> >
> >
> > ----------------------------------------
> > > From: ted.dunning@gmail.com
> > > Date: Mon=2C 22 Nov 2010 14:46:20 -0800
> > > Subject: Re: Lanczos Algorithm
> > > To: user@mahout.apache.org
> > >
> > > That seems like a lot. That would mean that have 10^14 =3D 100 trilli=
on
> > > nonzero elements which would take 10PB to store with one bit per non-=
zero
> > > element.
> > >
> > > Are there many totally zero rows?
> > >
> > > Can you estimate how many non-zero elements you have in all?
> > >
> >
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