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From Ted Dunning <>
Subject Re: SSVD Wrong Singular Vectors
Date Sat, 01 Sep 2012 05:55:46 GMT
Can you provide your test code?

What difference did you observe?

Did you account for the fact that your matrix is small enough that it
probably wasn't divided correctly?

On Sat, Sep 1, 2012 at 1:27 AM, Ahmed Elgohary <> wrote:

> Hi,
> I used mahout's stochastic svd implementation to find the singular vectors
> and the singular vectors of a small matrix 99x100. Then, I compared the
> results to the singular values and the singular vectors obtained using the
> svd function in matlab and the single threaded version of the ssvd. I got
> pretty much the same singular values using the 3 implementations. however,
> the singular vectors of mahout's ssvd were significantly different. I tried
> multiple values for the parameters P and Q but, that does not seem to solve
> the problem. Does MR implementation of the SSVD do extra approximations
> over the single threaded ssvd so their results might not be the same? Any
> advice how I can tune mahout's ssvd to get the same singular vectors of the
> single threaded ssvd?
> thanks,
> --ahmed

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