Singular Value Decomposition (SVD) is a popular approach in various network applications, such as link prediction and network parameter characterization. Incremental SVD approaches are proposed to process newly changed nodes and edges in dynamic networks. However, incremental SVD approaches suffer from serious error accumulation inevitably due to approximation on incremental updates. SVD restart is an effective approach to reset the aggregated error, but when to restart SVD for dynamic networks is not addressed in literature. In this paper, we propose TIMERS, Theoretically Instructed Maximum-Error-bounded Restart of SVD, a novel approach which optimally sets the restart time in order to reduce error accumulation in time. Specifically, we monitor the margin between reconstruction loss of incremental updates and the minimum loss in SVD model. To reduce the complexity of monitoring, we theoretically develop a lower bound of SVD minimum loss for dynamic networks and use the bound to replace the minimum loss in monitoring. By setting a maximum tolerated error as a threshold, we can trigger SVD restart automatically when the margin exceeds this threshold.We prove that the time complexity of our method is linear with respect to the number of local dynamic changes, and our method is general across different types of dynamic networks. We conduct extensive experiments on several synthetic and real dynamic networks. The experimental results demonstrate that our proposed method significantly outperforms the existing methods by reducing 27 to 42 in terms of the maximum error for dynamic network reconstruction when fixing the number of restarts. Our method reduces the number of restarts by 25 to 50 when fixing the maximum error tolerated.
Many methods have been proposed for network analysis @cite_4 @cite_18 @cite_2 . Among them, Singular Value Decomposition (SVD) is proven to be successful in many important network applications. For example, the singular vectors of an adjacency matrix or its variations, such as the transition matrix, can be used to represent nodes in the network @cite_10 . Spectral analysis usually involves calculating SVD on the Laplacian matrix of a network @cite_12 . The singular values, or the equivalent eigenvalues for undirected networks, are associated with the network parameters @cite_11 .
@cite_18 @cite_4 @cite_2 @cite_10 @cite_12 @cite_11
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The singular value decomposition (SVD) has been extensively used in engineering and statistical applications. This method was originally discovered by Eckart and Young in [Psychometrika, 1 (1936), pp. 211--218], where they considered the problem of low-rank approximation to a matrix. A natural generalization of the SVD is the problem of low-rank approximation to high order tensors, which we call the multidimensional SVD. In this paper, we investigate certain properties of this decomposition as well as numerical algorithms. This paper concerns accurate computation of the singular value decomposition (SVD) of an (m n ) matrix (A ). As is well known, cross-product matrix based SVD algorithms compute large singular values accurately but generally deliver poor small singular values. A new novel cross-product matrix based SVD method is proposed: (a) Use a backward stable algorithm to compute the eigenpairs of (A^ T A ) and take the square roots of the large eigenvalues of it as the large singular values of (A ) ; (b) form the Rayleigh quotient of (A^ T A ) with respect to the matrix consisting of the computed eigenvectors associated with the computed small eigenvalues of (A^ T A ) ; (c) compute the eigenvalues of the Rayleigh quotient and take the square roots of them as the small singular values of (A ). A detailed quantitative error analysis is conducted on the method. It is proved that if small singular values are well separated from the large ones then the method can compute the small ones accurately up to the order of the unit roundoff ( ). An algorithm is developed that is not only cheaper than the standard Golub–Reinsch and Chan SVD algorithms but also can update or downdate a new SVD by adding or deleting a row and compute certain refined Ritz vectors for large matrix eigenproblems at very low cost. Several variants of the algorithm are proposed that compute some or all parts of the SVD. Typical numerical examples confirm the high accuracy of our algorithm. Abstract Most methods for calculating the SVD (singular value decomposition) require to first bidiagonalize the matrix. The blocked reduction of a general, dense matrix to bidiagonal form, as implemented in ScaLAPACK, does about one half of the operations with BLAS3. By subdividing the reduction into two stages dense → banded and banded → bidiagonal with cubic and quadratic arithmetic costs, respectively, we are able to carry out a much higher portion of the calculations in matrix–matrix multiplications. Thus, higher performance can be expected. This paper presents and compares three parallel techniques for reducing a full matrix to banded form. (The second reduction stage is described in another paper [B. Lang, Parallel Comput. 22 (1996) 1–18]). Numerical experiments on the Intel Paragon and IBM SP 1 distributed memory parallel computers demonstrate that the two-stage reduction approach can be significantly superior if only the singular values are required. We present four numerical methods for computing the singular value decomposition SVD of large sparse matrices on a multiprocessor architecture. We emphasize Lanczos and subspace iteration-based methods for determining several of the largest singular triplets singular values and corresponding left- and right-singular vectors for sparse matrices arising from two practical applications: information retrieval and seismic reflection tomography. The target architectures for our implementations are the CRAY-2S 4-128 and Alliant FX 80. The sparse SVD problem is well motivated by recent information-retrieval techniques in which dominant singular values and their corresponding singular vectors of large sparse term-document matrices are desired, and by nonlinear inverse problems from seismic tomography applications which require approximate pseudo-inverses of large sparse Jacobian matrices. This research may help advance the development of future out-of-core sparse SVD methods, which can be used, for example, to handle extremely large sparse matrices 0 ? 106 rows or columns associated with extremely large databases in query-based information-retrieval applications.