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From Jake Mannix <>
Subject Re: Fwd: A MapReduce Algorithm for Matrix Multiplication
Date Wed, 09 Dec 2009 03:05:50 GMT
On Tue, Dec 8, 2009 at 6:47 PM, Zhengguo 'Mike' SUN

> Hi Jake,
> I am implementing the classical multiplicative update rule of NMF. The
> matrix to be factorized is really big and sparse. Are you suggesting that I
> can use some specialised algorithms for sparse matrix instead of the
> standard multiplication algorithm? But what algorithms are you referring to?
> Could you please provide some pointers?

So given your input matrix X, you're trying to find non-negative matrices W
(thin matrix, with few long dense columns) and H (wide matrix, with few long
dense rows) which minimize || X - WH ||, right, where || * || is the
Froebenius norm, right?

I'm just suggesting that you don't even compute entries in X - WH where X
has missing data - optimize treating those values as unknown, not "zero".


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