Research Institute for Advanced Computer Science

About: Research Institute for Advanced Computer Science is a facility organization based out in Mountain View, California, United States. It is known for research contribution in the topics: Model checking & Parallel algorithm. The organization has 180 authors who have published 418 publications receiving 17072 citations.

An improved Newton interaction for the generalized inverse of a Matrix, with applications

Abstract: Pan and Reif have shown that Newton iteration may be used to compute the inverse of an $n \times n$, well-conditioned matrix in parallel time $O(\log ^2 n)$ and that this computation is processor efficient. Since the algorithm essentially amounts to a sequence of matrix–matrix multiplications, it can be implemented with great efficiency on systolic arrays and parallel computers.Newton's method is expensive in terms of the arithmetic operation count. In this paper the cost of Newton's method is reduced with several new acceleration procedures. A speedup by a factor of two is obtained for arbitrary input matrices; for symmetric positive definite matrices, the factor is four. It is also shown that the accelerated procedure is a form of Tchebychev acceleration, whereas Newton's method uses a Neumann series approximation.In addition, Newton-like procedures are developed for a number of important related problems. It is also shown how to compute the nearest matrices of lower rank to a given matrix A, the generalized inverses of these nearby matrices, their ranks (as a function of their distances from A), and projections onto subspaces spanned by singular vectors; such computations are impodrtant in signal processing applications. Furthermore, it is demonstrated that the numerical instability of Newton's method when applied to a singular matrix is absent from these improved methods. Finally, the use of these tools to devise new polylog time parallel algorithms for the singular value decomposition is explored.

Back to the Future for Consistency-Based Trajectory Tracking

Abstract: Given a model of a physical process and a sequence of commands and observations received over time, the task of an autonomous controller is to determine the likely states of the process and the actions required to move the process to a desired configuration. We introduce a representation and algorithms for incrementally generating approximate belief states for a restricted but relevant class of partially observable Markov decision processes with very large state spaces. The algorithm presented incrementally generates, rather than revises, an approximate belief state at any point by abstracting and summarizing segments of the likely trajectories of the process. This enables applications to efficiently maintain a partial belief state when it remains consistent with observations and revisit past assumptions about the process' evolution when the belief state is ruled out. The system presented has been implemented and results on examples from the domain of spacecraft control are presented.

Quantum Optimization of Fully-Connected Spin Glasses

Abstract: The Sherrington-Kirkpatrick model with random $\pm1$ couplings is programmed on the D-Wave Two annealer featuring 509 qubits interacting on a Chimera-type graph. The performance of the optimizer compares and correlates to simulated annealing. When considering the effect of the static noise, which degrades the performance of the annealer, one can estimate an improvement on the comparative scaling of the two methods in favor of the D-Wave machine. The optimal choice of parameters of the embedding on the Chimera graph is shown to be associated to the emergence of the spin-glass critical temperature of the embedded problem.

A survey and comparison of fault-tolerant multistage interconnection networks

Abstract: Intrinsically fault-tolerant multistage interconnection networks (MINs) are surveyed, categorizing the MINs by the amount of hardware modifications they use to provide redundancy. The diversity of such MINs and the scope of fault-tolerance techniques are examined. A hypothetical MIN with ideal engineering characteristics is defined, and the surveyed MINs are compared to this standard.