89,337 research outputs found

    Six networks on a universal neuromorphic computing substrate

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    In this study, we present a highly configurable neuromorphic computing substrate and use it for emulating several types of neural networks. At the heart of this system lies a mixed-signal chip, with analog implementations of neurons and synapses and digital transmission of action potentials. Major advantages of this emulation device, which has been explicitly designed as a universal neural network emulator, are its inherent parallelism and high acceleration factor compared to conventional computers. Its configurability allows the realization of almost arbitrary network topologies and the use of widely varied neuronal and synaptic parameters. Fixed-pattern noise inherent to analog circuitry is reduced by calibration routines. An integrated development environment allows neuroscientists to operate the device without any prior knowledge of neuromorphic circuit design. As a showcase for the capabilities of the system, we describe the successful emulation of six different neural networks which cover a broad spectrum of both structure and functionality

    QRAT+: Generalizing QRAT by a More Powerful QBF Redundancy Property

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    The QRAT (quantified resolution asymmetric tautology) proof system simulates virtually all inference rules applied in state of the art quantified Boolean formula (QBF) reasoning tools. It consists of rules to rewrite a QBF by adding and deleting clauses and universal literals that have a certain redundancy property. To check for this redundancy property in QRAT, propositional unit propagation (UP) is applied to the quantifier free, i.e., propositional part of the QBF. We generalize the redundancy property in the QRAT system by QBF specific UP (QUP). QUP extends UP by the universal reduction operation to eliminate universal literals from clauses. We apply QUP to an abstraction of the QBF where certain universal quantifiers are converted into existential ones. This way, we obtain a generalization of QRAT we call QRAT+. The redundancy property in QRAT+ based on QUP is more powerful than the one in QRAT based on UP. We report on proof theoretical improvements and experimental results to illustrate the benefits of QRAT+ for QBF preprocessing.Comment: preprint of a paper to be published at IJCAR 2018, LNCS, Springer, including appendi

    A Universal Parallel Two-Pass MDL Context Tree Compression Algorithm

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    Computing problems that handle large amounts of data necessitate the use of lossless data compression for efficient storage and transmission. We present a novel lossless universal data compression algorithm that uses parallel computational units to increase the throughput. The length-NN input sequence is partitioned into BB blocks. Processing each block independently of the other blocks can accelerate the computation by a factor of BB, but degrades the compression quality. Instead, our approach is to first estimate the minimum description length (MDL) context tree source underlying the entire input, and then encode each of the BB blocks in parallel based on the MDL source. With this two-pass approach, the compression loss incurred by using more parallel units is insignificant. Our algorithm is work-efficient, i.e., its computational complexity is O(N/B)O(N/B). Its redundancy is approximately Blog(N/B)B\log(N/B) bits above Rissanen's lower bound on universal compression performance, with respect to any context tree source whose maximal depth is at most log(N/B)\log(N/B). We improve the compression by using different quantizers for states of the context tree based on the number of symbols corresponding to those states. Numerical results from a prototype implementation suggest that our algorithm offers a better trade-off between compression and throughput than competing universal data compression algorithms.Comment: Accepted to Journal of Selected Topics in Signal Processing special issue on Signal Processing for Big Data (expected publication date June 2015). 10 pages double column, 6 figures, and 2 tables. arXiv admin note: substantial text overlap with arXiv:1405.6322. Version: Mar 2015: Corrected a typ

    Fluctuating hydrodynamics and turbulence in a rotating fluid: Universal properties

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    We analyze the statistical properties of three-dimensional (3d3d) turbulence in a rotating fluid. To this end we introduce a generating functional to study the statistical properties of the velocity field v\bf v. We obtain the master equation from the Navier-Stokes equation in a rotating frame and thence a set of exact hierarchical equations for the velocity structure functions for arbitrary angular velocity Ω\mathbf \Omega. In particular we obtain the {\em differential forms} for the analogs of the well-known von Karman-Howarth relation for 3d3d fluid turbulence. We examine their behavior in the limit of large rotation. Our results clearly suggest dissimilar statistical behavior and scaling along directions parallel and perpendicular to Ω\mathbf \Omega. The hierarchical relations yield strong evidence that the nature of the flows for large rotation is not identical to pure two-dimensional flows. To complement these results, by using an effective model in the small-Ω\Omega limit, within a one-loop approximation, we show that the equal-time correlation of the velocity components parallel to Ω\mathbf \Omega displays Kolmogorov scaling q5/3q^{-5/3}, where as for all other components, the equal-time correlators scale as q3q^{-3} in the inertial range where q\bf q is a wavevector in 3d3d. Our results are generally testable in experiments and/or direct numerical simulations of the Navier-Stokes equation in a rotating frame.Comment: 24 pages in preprint format; accepted for publication in Phys. Rev. E (2011

    Dynamic escape game

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    We introduce Dynamic Escape Game (DEC), a tool that provides emergency evacuation plans in situations where some of the escape paths may become unavailable at runtime. We formalize the setting as a reachability two-player turn-based game where the universal player has the power of inhibiting at runtime some moves to the existential player. Thus, the universal player can change the structure of the game arena along a play. DEC uses a graphical interface to depict the game and displays a winning play whenever it exists
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