CODEWITHSUNDEEP
rmatlaboctavesvd
Pierre
Pierre

Reputation: 1246

Full SVD of a large sparse matrix (where only the eigenvalues are required)

I am trying to run the full SVD of a large (120k x 600k) and sparse (0,1% of non-null values) matrix M. Due to memory limitation all my previous attempts failed (with SVDLIBC, Octave, and R) and I am (almost) resigned to exploring other approaches to my problem (LSA).

However, at the moment, I am only interested in the eigenvalues of the diagonal matrix S and not in the left/right singular vectors (matrices U and V).

Is there a way to compute those singular values without storing in memory the dense matrix M and/or the singular vector matrices U and V?

Any help will be greatly appreciated.

[EDIT] My server configuration: 3,5GHz/3,9GHz (6 cores / 12 threads) 128GB of RAM

Upvotes: 2

Views: 1685

Answers (2)

CuboidalVenus
CuboidalVenus

Reputation: 11

How comfortable are you with Fortran? I think you should be able to complete the computations using prebuilt packages available here and/or here. Also, if you're open to C++ and a decomposition using randomized and re-orthonormalized matrices, you can try the code at the google code project called redsvd. (I can't post the link because I don't have the requisite reputation for three links, but you can search for redsvd and find it readily.)

Upvotes: 1

sebas
sebas

Reputation: 879

Looking for the meaning of that values (elements of matrix S from a SVD decomposition) in wikipedia we get:

The non-zero singular values of M (found on the diagonal entries of Σ) are the square roots of the non-zero eigenvalues of both M*M and MM*

So you can look for the eigenvalues of the matrix A*A' (120k x 120k) without explicitly build the matrix, of course.

By the way, I dont think you are interested in ALL the eigenvalues (or singular values) for a matrix with such a dimensions. I do not think that any algorithm will give enough accurate results.

Upvotes: 1

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