OpenRaiser/Intern-Atlas huggingface dataset:
Knightian Robustness from Regret Minimization
Venue: arXiv cs.GT 2014
Year: 2014

We consider auctions in which the players have very limited knowledge about their own valuations. Specifically, the only information that a Knightian player $i$ has about the profile of true valuations, $θ^*$, consists of a set of distributions, from one of which $θ_i^*$ has been drawn. We analyze the social-welfare performance of the VCG mechanism, for unrestricted combinatorial auctions, when Knightian players that either (a) choose a regret-minimizing strategy, or (b) resort to regret minimization only to refine further their own sets of undominated strategies, if needed. We prove that this performance is very good.
tinyNBI: Distilling an API from essential OpenFlow abstractions
Venue: arXiv cs.NI 2014
Year: 2014

If simplicity is a key strategy for success as a network protocol OpenFlow is not winning. At its core OpenFlow presents a simple idea, which is a network switch data plane abstraction along with a control protocol for manipulating that abstraction. The result of this idea has been far from simple: a new version released each year, five active versions, com- plex feature dependencies, unstable version negotiation, lack of state machine definition, etc. This complexity represents roadblocks for network, software, and hardware engineers. We have distilled the core abstractions present in 5 existing versions of OpenFlow and refactored them into a simple API called tinyNBI. Our work does not provide high-level network abstractions (address pools, VPN maps, etc.), instead it focuses on providing a clean low level interface that supports the development of these higher layer abstractions. The goal of tinyNBI is to allow configuration of all existing OpenFlow abstractions without having to deal with the unique personalities of each version of OpenFlow or their level of support in target switches.
WaterRPG: A Graph-based Dynamic Watermarking Model for Software Protection
Venue: arXiv cs.MM 2014
Year: 2014

Software watermarking involves embedding a unique identifier or, equivalently, a watermark value within a software to prove owner's authenticity and thus to prevent or discourage copyright infringement. Towards the embedding process, several graph theoretic watermarking algorithmic techniques encode the watermark values as graph structures and embed them in application programs. Recently, we presented an efficient codec system for encoding a watermark number $w$ as a reducible permutation graph $F[π^*]$ through the use of self-inverting permutations $π^*$. In this paper, we propose a dynamic watermarking model, which we call WaterRPG, for embedding the watermark graph $F[π^*]$ into an application program $P$. The main idea behind the proposed watermarking model is a systematic use of appropriate calls of specific functions of the program $P$. More precisely, for a specific input $I_{key}$ of the program $P$, our model takes the dynamic call-graph $G(P, I_{key})$ of $P$ and the watermark graph $F[π^*]$, and produces the watermarked program $P^*$ having the following key property: its dynamic call-graph $G(P^*, I_{key})$ is isomorphic to the watermark graph $F[π^*]$. Within this idea the program $P^*$ is produced by only altering appropriate calls of specific functions of the input application program $P$. We have implemented our watermarking model WaterRPG in real application programs and evaluated its functionality under various and broadly used watermarking assessment criteria. The evaluation results show that our model efficiently watermarks Java application programs with respect to several watermarking metrics like data-rate, bytecode instructions overhead, resiliency, time and space efficiency. Moreover, the embedded watermarks withstand several software obfuscation and optimization attacks.
One-sided asymptotically mean stationary channels
Venue: arXiv cs.IT 2014
Year: 2014

This paper proposes an analysis of asymptotically mean stationary (AMS) communication channels. A hierarchy based on stability properties (stationarity, quasi-stationarity, recurrence and asymptotically mean stationarity) of channels is identified. Stationary channels are a subclass of quasi-stationary channels which are a subclass of recurrent AMS channels which are a subclass of AMS channels. These classes are proved to be stable under Markovian composition of channels (e.g., the cascade of AMS channels is an AMS channel). Characterizations of channels of each class are given. Some properties of the quasi-stationary mean of a channel are established. Finally, ergodicity conditions of AMS channels are gathered.
Procesamiento topo-geométrico de imágenes neuronales
Venue: arXiv cs.SC 2014
Year: 2014

Fruit of the relationship of our research group with the team coordinated by the biologist Miguel Morales (http://spineup.es), we have applied different topo-geometric techniques for neuronal image processing. The images, captured with a powerful confocal microscope, allow to study the evolution of synaptic density under the influence of various substances, with the aim of studying neurodegenerative diseases like Alzheimer. In the paper we make a brief review of the techniques that appear in our bioinformatic problems, including the calculation of ordinary and persistent homology (for which one can use the program Kenzo for symbolic computation in algebraic topology ) and classical problems of digital topology as skeleton location and path tracking. We focus on some particular cases of recent application, with which we will illustrate the previous techniques.
Optimized imaging using non-rigid registration
Venue: arXiv cs.CV 2014
Year: 2014

The extraordinary improvements of modern imaging devices offer access to data with unprecedented information content. However, widely used image processing methodologies fall far short of exploiting the full breadth of information offered by numerous types of scanning probe, optical, and electron microscopies. In many applications, it is necessary to keep measurement intensities below a desired threshold. We propose a methodology for extracting an increased level of information by processing a series of data sets suffering, in particular, from high degree of spatial uncertainty caused by complex multiscale motion during the acquisition process. An important role is played by a nonrigid pixel-wise registration method that can cope with low signal-to-noise ratios. This is accompanied by formulating objective quality measures which replace human intervention and visual inspection in the processing chain. Scanning transmission electron microscopy of siliceous zeolite material exhibits the above-mentioned obstructions and therefore serves as orientation and a test of our procedures.
Quantifying Information Overload in Social Media and its Impact on Social Contagions
Venue: arXiv cs.SI 2014
Year: 2014

Information overload has become an ubiquitous problem in modern society. Social media users and microbloggers receive an endless flow of information, often at a rate far higher than their cognitive abilities to process the information. In this paper, we conduct a large scale quantitative study of information overload and evaluate its impact on information dissemination in the Twitter social media site. We model social media users as information processing systems that queue incoming information according to some policies, process information from the queue at some unknown rates and decide to forward some of the incoming information to other users. We show how timestamped data about tweets received and forwarded by users can be used to uncover key properties of their queueing policies and estimate their information processing rates and limits. Such an understanding of users' information processing behaviors allows us to infer whether and to what extent users suffer from information overload. Our analysis provides empirical evidence of information processing limits for social media users and the prevalence of information overloading. The most active and popular social media users are often the ones that are overloaded. Moreover, we find that the rate at which users receive information impacts their processing behavior, including how they prioritize information from different sources, how much information they process, and how quickly they process information. Finally, the susceptibility of a social media user to social contagions depends crucially on the rate at which she receives information. An exposure to a piece of information, be it an idea, a convention or a product, is much less effective for users that receive information at higher rates, meaning they need more exposures to adopt a particular contagion.
A Molecular Communication Link for Monitoring in Confined Environments
Venue: arXiv cs.ET 2014
Year: 2014

In this paper, we consider a molecular diffusion based communications link that can reliably transport data over-the-air. We show that the system can also reliably transport data across confined structural environments, especially in cases where conventional electromagnetic (EM) wave based systems may fail. In particular, this paper compares the performance of our proprietary molecular communication test-bed with Zigbee wireless sensors in a metal pipe network that does not act as a radio wave-guide. The paper first shows that a molecular-based communication link's performance is determined primarily by the delay time spread of the pulse response. The paper go on to show that molecular-based systems can transmit more reliably in complex and confined structural environments than conventional EM-based systems. The paper then utilizes empirical data to find relationships between the received radio signal strength, the molecular pulse spread, data rate (0.1 bits/s) and the structural propagation environment.
Vulnerability Scanners-A Proactive Approach To Assess Web Application Security
Venue: arXiv cs.CR 2014
Year: 2014

With the increasing concern for security in the network, many approaches are laid out that try to protect the network from unauthorised access. New methods have been adopted in order to find the potential discrepancies that may damage the network. Most commonly used approach is the vulnerability assessment. By vulnerability, we mean, the potential flaws in the system that make it prone to the attack. Assessment of these system vulnerabilities provide a means to identify and develop new strategies so as to protect the system from the risk of being damaged. This paper focuses on the usage of various vulnerability scanners and their related methodology to detect the various vulnerabilities available in the web applications or the remote host across the network and tries to identify new mechanisms that can be deployed to secure the network.
Management of dangerous goods in container terminal with MAS model
Venue: arXiv cs.MA 2014
Year: 2014

In a container terminal, many operations occur within the storage area: containers import, containers export and containers shifting. All these operations require the respect of many rules and even laws in order to guarantee the port safety and to prevent risks, especially when hazardous material is concerned. In this paper, we propose a hybrid architecture, using a Cellular Automaton and a Multi-Agent System to handle the dangerous container storage problem. It is an optimization problem since the aim is to improve the container terminal configuration, that is, the way hazardous containers are dispatched through the terminal to improve its security. In our model, we consider containers as agents, in order to use a Multi-Agent System for the decision aid software, and a Cellular Automaton for modelling the terminal itself. To validate our approach many tests have been performed and the results show the relevance of our model.
Delay Analysis of Multichannel Opportunistic Spectrum Access MAC Protocols
Venue: arXiv cs.NI 2014
Year: 2014

We provide in this paper a comprehensive delay and queueing analysis for two baseline medium access control (MAC) protocols for multi-user cognitive radio (CR) networks and investigate the impact of different network parameters, such as packet size, Aloha-type medium access probability and number of channels on the system performance. In addition to an accurate Markov chain, which follows the queue status of all users, several lower complexity queueing theory approximations are provided. Accuracy and performance of the proposed analytical approximations are verified with extensive simulations. It is observed that for CR networks using an Aloha-type access to the control channel, a buffering MAC protocol, where in case of interruption the CR user waits for the primary user to vacate the channel before resuming the transmission, outperforms a switching MAC protocol, where the CR user vacates the channel in case of appearance of primary users and then compete again to gain access to a new channel. The reason is that the delay bottleneck for both protocols is the time required to successfully access the control channel, which occurs more frequently for the switching MAC protocol. We also propose a user clustering approach, where users are divided into clusters with a separate control channel per cluster, and observe that it can significantly improve the performance by reducing the number of competing users per control channel.
Acceleration of a Full-scale Industrial CFD Application with OP2
Venue: arXiv cs.CE 2014
Year: 2014

Hydra is a full-scale industrial CFD application used for the design of turbomachinery at Rolls Royce plc. It consists of over 300 parallel loops with a code base exceeding 50K lines and is capable of performing complex simulations over highly detailed unstructured mesh geometries. Unlike simpler structured-mesh applications, which feature high speed-ups when accelerated by modern processor architectures, such as multi-core and many-core processor systems, Hydra presents major challenges in data organization and movement that need to be overcome for continued high performance on emerging platforms. We present research in achieving this goal through the OP2 domain-specific high-level framework. OP2 targets the domain of unstructured mesh problems and follows the design of an active library using source-to-source translation and compilation to generate multiple parallel implementations from a single high-level application source for execution on a range of back-end hardware platforms. We chart the conversion of Hydra from its original hand-tuned production version to one that utilizes OP2, and map out the key difficulties encountered in the process. To our knowledge this research presents the first application of such a high-level framework to a full scale production code. Specifically we show (1) how different parallel implementations can be achieved with an active library framework, even for a highly complicated industrial application such as Hydra, and (2) how different optimizations targeting contrasting parallel architectures can be applied to the whole application, seamlessly, reducing developer effort and increasing code longevity. Performance results demonstrate that not only the same runtime performance as that of the hand-tuned original production code could be achieved, but it can be significantly improved on conventional processor systems. Additionally, we achieve further...
Reduction Techniques for Graph Isomorphism in the Context of Width Parameters
Venue: arXiv cs.DM 2014
Year: 2014

We study the parameterized complexity of the graph isomorphism problem when parameterized by width parameters related to tree decompositions. We apply the following technique to obtain fixed-parameter tractability for such parameters. We first compute an isomorphism invariant set of potential bags for a decomposition and then apply a restricted version of the Weisfeiler-Lehman algorithm to solve isomorphism. With this we show fixed-parameter tractability for several parameters and provide a unified explanation for various isomorphism results concerned with parameters related to tree decompositions. As a possibly first step towards intractability results for parameterized graph isomorphism we develop an fpt Turing-reduction from strong tree width to the a priori unrelated parameter maximum degree.
Asynchronous Orthogonal Differential Decoding for Multiple Access Channels
Venue: arXiv cs.IT 2014
Year: 2014

We propose several differential decoding schemes for asynchronous multi-user MIMO systems based on orthogonal space-time block codes (OSTBCs) where neither the transmitters nor the receiver has knowledge of the channel. First, we derive novel low complexity differential decoders by performing interference cancelation in time and employing different decoding methods. The decoding complexity of these schemes grows linearly with the number of users. We then present additional differential decoding schemes that perform significantly better than our low complexity decoders and outperform the existing synchronous differential schemes but require higher decoding complexity compared to our low complexity decoders. The proposed schemes work for any square OSTBC, any constant amplitude constellation, any number of users, and any number of receive antennas. Furthermore, we analyze the diversity of the proposed schemes and derive conditions under which our schemes provide full diversity. For the cases of two and four transmit antennas, we provide examples of PSK constellations to achieve full diversity. Simulation results show that our differential schemes provide good performance. To the best of our knowledge, the proposed differential detection schemes are the first differential schemes for asynchronous multi-user systems.
Tile optimization for area in FPGA based hardware acceleration of peptide identification
Venue: arXiv cs.CE 2014
Year: 2014

Advances in life sciences over the last few decades have lead to the generation of a huge amount of biological data. Computing research has become a vital part in driving biological discovery where analysis and categorization of biological data are involved. String matching algorithms can be applied for protein/gene sequence matching and with the phenomenal increase in the size of string databases to be analyzed, software implementations of these algorithms seems to have hit a hard limit and hardware acceleration is increasingly being sought. Several hardware platforms such as Field Programmable Gate Arrays (FPGA), Graphics Processing Units (GPU) and Chip Multi Processors (CMP) are being explored as hardware platforms. In this paper, we give a comprehensive overview of the literature on hardware acceleration of string matching algorithms, we take an FPGA hardware exploration and expedite the design time by a design automation technique. Further, our design automation is also optimized for better hardware utilization through optimizing the number of peptides that can be represented in an FPGA tile. The results indicate significant improvements in design time and hardware utilization which are reported in this paper.
Heterogeneous processor pipeline for a product cipher application
Venue: arXiv cs.AR 2014
Year: 2014

Processing data received as a stream is a task commonly performed by modern embedded devices, in a wide range of applications such as multimedia (encoding/decoding/ playing media), networking (switching and routing), digital security, scientific data processing, etc. Such processing normally tends to be calculation intensive and therefore requiring significant processing power. Therefore, hardware acceleration methods to increase the performance of such applications constitute an important area of study. In this paper, we present an evaluation of one such method to process streaming data, namely multi-processor pipeline architecture. The hardware is based on a Multiple-Processor System on Chip (MPSoC), using a data encryption algorithm as a case study. The algorithm is partitioned on a coarse grained level and mapped on to an MPSoC with five processor cores in a pipeline, using specifically configured Xtensa LX3 cores. The system is then selectively optimized by strengthening and pruning the resources of each processor core. The optimized system is evaluated and compared against an optimal single-processor System on Chip (SoC) for the same application. The multiple-processor pipeline system for data encryption algorithms used was observed to provide significant speed ups, up to 4.45 times that of the single-processor system, which is close to the ideal speed up from a five-stage pipeline.
On the Outage Probability of the Full-Duplex Interference-Limited Relay Channel
Venue: arXiv cs.IT 2014
Year: 2014

In this paper, we study the performance, in terms of the asymptotic error probability, of a user which communicates with a destination with the aid of a full-duplex in-band relay. We consider that the network is interference-limited, and interfering users are distributed as a Poisson point process. In this case, the asymptotic error probability is upper bounded by the outage probability (OP). We investigate the outage behavior for well-known cooperative schemes, namely, decode-and-forward (DF) and compress-and-forward (CF) considering fading and path loss. For DF we determine the exact OP and develop upper bounds which are tight in typical operating conditions. Also, we find the correlation coefficient between source and relay signals which minimizes the OP when the density of interferers is small. For CF, the achievable rates are determined by the spatial correlation of the interferences, and a straightforward analysis isn't possible. To handle this issue, we show the rate with correlated noises is at most one bit worse than with uncorrelated noises, and thus find an upper bound on the performance of CF. These results are useful to evaluate the performance and to optimize relaying schemes in the context of full-duplex wireless networks.
Learning detectors quickly using structured covariance matrices
Venue: arXiv cs.CV 2014
Year: 2014

Computer vision is increasingly becoming interested in the rapid estimation of object detectors. Canonical hard negative mining strategies are slow as they require multiple passes of the large negative training set. Recent work has demonstrated that if the distribution of negative examples is assumed to be stationary, then Linear Discriminant Analysis (LDA) can learn comparable detectors without ever revisiting the negative set. Even with this insight, however, the time to learn a single object detector can still be on the order of tens of seconds on a modern desktop computer. This paper proposes to leverage the resulting structured covariance matrix to obtain detectors with identical performance in orders of magnitude less time and memory. We elucidate an important connection to the correlation filter literature, demonstrating that these can also be trained without ever revisiting the negative set.
Axiomatization of Finite Algebras
Venue: arXiv cs.LO 2014
Year: 2014

We show that the set of all formulas in n variables valid in a finite class A of finite algebras is always a regular tree language, and compute a finite axiom set for A. We give a rational reconstruction of Barzdins' liquid flow algorithm (Barzdin+Barzdin, 1991). We show a sufficient condition for the existence of a class A of prototype algebras for a given theory T. Such a set allows us to prove T |= p simply by testing whether p holds in A.
Slime mould electronic oscillators
Venue: arXiv cs.ET 2014
Year: 2014

We construct electronic oscillator from acellular slime mould Physarum polycephalum. The slime mould oscillator is made of two electrodes connected by a protoplasmic tube of the living slime mould. A protoplasmic tube has an average resistance of 3~MOhm. The tube's resistance is changing over time due to peristaltic contractile activity of the tube. The resistance of the protoplasmic tube oscillates with average period of 73~sec and average amplitude of 0.6~MOhm. We present experimental laboratory results on dynamics of Physarum oscillator under direct current voltage up to 15~V and speculate that slime mould P. polycephalum can be employed as a living electrical oscillator in biological and hybrid circuits.