OpenRaiser/Intern-Atlas huggingface dataset:
Sampling approach to sparse approximation problem: determining degrees of freedom by simulated annealing
Venue: arXiv cs.IT 2016
Year: 2016

The approximation of a high-dimensional vector by a small combination of column vectors selected from a fixed matrix has been actively debated in several different disciplines. In this paper, a sampling approach based on the Monte Carlo method is presented as an efficient solver for such problems. Especially, the use of simulated annealing (SA), a metaheuristic optimization algorithm, for determining degrees of freedom (the number of used columns) by cross validation is focused on and tested. Test on a synthetic model indicates that our SA-based approach can find a nearly optimal solution for the approximation problem and, when combined with the CV framework, it can optimize the generalization ability. Its utility is also confirmed by application to a real-world supernova data set.
Contextual trace refinement for concurrent objects: Safety and progress
Venue: arXiv cs.DC 2016
Year: 2016

Correctness of concurrent objects is defined in terms of safety properties such as linearizability, sequential consistency, and quiescent consistency, and progress properties such as wait-, lock-, and obstruction-freedom. These properties, however, only refer to the behaviours of the object in isolation, which does not tell us what guarantees these correctness conditions on concurrent objects provide to their client programs. This paper investigates the links between safety and progress properties of concurrent objects and a form of trace refinement for client programs, called contextual trace refinement. In particular, we show that linearizability together with a minimal notion of progress are sufficient properties of concurrent objects to ensure contextual trace refinement, but sequential consistency and quiescent consistency are both too weak. Our reasoning is carried out in the action systems framework with procedure calls, which we extend to cope with non-atomic operations.
Optimized Polynomial Evaluation with Semantic Annotations
Venue: arXiv cs.PL 2016
Year: 2016

In this paper we discuss how semantic annotations can be used to introduce mathematical algorithmic information of the underlying imperative code to enable compilers to produce code transformations that will enable better performance. By using this approaches not only good performance is achieved, but also better programmability, maintainability and portability across different hardware architectures. To exemplify this we will use polynomial equations of different degrees.
Low Complexity Hybrid Precoding and Channel Estimation Based on Hierarchical Multi-Beam Search for Millimeter-Wave MIMO Systems
Venue: arXiv cs.IT 2016
Year: 2016

In millimeter-wave (mmWave) MIMO systems, while a hybrid digital/analog precoding structure offers the potential to increase the achievable rate, it also faces the challenge of the need of a low-complexity design. In specific, the hybrid precoding may require matrix operations with a scale of antenna size, which is generally large in mmWave communication. Moreover, the channel estimation is also rather time consuming due to the large number of antennas at both Tx/Rx sides. In this paper, a low-complexity hybrid precoding and channel estimation approach is proposed. In the channel estimation phase, a hierarchical multi-beam search scheme is proposed to fast acquire $N_{\rm{S}}$ (the number of streams) multipath components (MPCs)/clusters with the highest powers. In the hybrid precoding phase, the analog and digital precodings are decoupled. The analog precoding is designed to steer along the $N_{\rm{S}}$ acquired MPCs/clusters at both Tx/Rx sides, shaping an equivalent $N_{\rm{S}}\times N_{\rm{S}}$ baseband channel, while the digital precoding performs operations in the baseband with the reduced-scale channel. Performance evaluations show that, compared with a state-of-the-art scheme, while achieving a close or even better performance when the number of radio-frequency (RF) chains or streams is small, both the computational complexity of the hybrid precoding and the time complexity of the channel estimation are greatly reduced.
New Algorithms for Maximum Disjoint Paths Based on Tree-Likeness
Venue: arXiv cs.DS 2016
Year: 2016

We study the classical NP-hard problems of finding maximum-size subsets from given sets of $k$ terminal pairs that can be routed via edge-disjoint paths (MaxEDP) or node-disjoint paths (MaxNDP) in a given graph. The approximability of MaxEDP/NDP is currently not well understood; the best known lower bound is $Ω(\log^{1/2-ε}{n})$, assuming NP$~\not\subseteq~$ZPTIME$(n^{\mathrm{poly}\log n})$. This constitutes a significant gap to the best known approximation upper bound of $O(\sqrt{n})$ due to Chekuri et al. (2006) and closing this gap is currently one of the big open problems in approximation algorithms. In their seminal paper, Raghavan and Thompson (Combinatorica, 1987) introduce the technique of randomized rounding for LPs; their technique gives an $O(1)$-approximation when edges (or nodes) may be used by $O(\frac{\log n}{\log\log n})$ paths. In this paper, we strengthen the above fundamental results. We provide new bounds formulated in terms of the feedback vertex set number $r$ of a graph, which measures its vertex deletion distance to a forest. In particular, we obtain the following. * For MaxEDP, we give an $O(\sqrt{r}\cdot \log^{1.5}{kr})$-approximation algorithm. As $r\leq n$, up to logarithmic factors, our result strengthens the best known ratio $O(\sqrt{n})$ due to Chekuri et al. * Further, we show how to route $Ω(\mathrm{OPT})$ pairs with congestion $O(\frac{\log{kr}}{\log\log{kr}})$, strengthening the bound obtained by the classic approach of Raghavan and Thompson. * For MaxNDP, we give an algorithm that gives the optimal answer in time $(k+r)^{O(r)}\cdot n$. If $r$ is at most triple-exponential in $k$, this improves the best known algorithm for MaxNDP with parameter $k$, by Kawarabayashi and Wollan (STOC 2010). We complement these positive results by proving that MaxEDP is NP-hard even for $r=1$, and MaxNDP is W$[1]$-hard for parameter $r$.
Proof of Threshold Saturation for Spatially Coupled Sparse Superposition Codes
Venue: arXiv cs.IT 2016
Year: 2016

Recently, a new class of codes, called sparse superposition or sparse regression codes, has been proposed for communication over the AWGN channel. It has been proven that they achieve capacity using power allocation and various forms of iterative decoding. Empirical evidence has also strongly suggested that the codes achieve capacity when spatial coupling and approximate message passing decoding are used, without need of power allocation. In this note we prove that state evolution (which tracks message passing) indeed saturates the potential threshold of the underlying code ensemble, which approaches in a proper limit the optimal threshold. Our proof uses ideas developed in the theory of low-density parity-check codes and compressive sensing.
Online Learning to Rank with Feedback at the Top
Venue: arXiv cs.LG 2016
Year: 2016

We consider an online learning to rank setting in which, at each round, an oblivious adversary generates a list of $m$ documents, pertaining to a query, and the learner produces scores to rank the documents. The adversary then generates a relevance vector and the learner updates its ranker according to the feedback received. We consider the setting where the feedback is restricted to be the relevance levels of only the top $k$ documents in the ranked list for $k \ll m$. However, the performance of learner is judged based on the unrevealed full relevance vectors, using an appropriate learning to rank loss function. We develop efficient algorithms for well known losses in the pointwise, pairwise and listwise families. We also prove that no online algorithm can have sublinear regret, with top-1 feedback, for any loss that is calibrated with respect to NDCG. We apply our algorithms on benchmark datasets demonstrating efficient online learning of a ranking function from highly restricted feedback.
A Real-Time and Energy-Efficient Implementation of Difference-of-Gaussian with Flexible Thin-Film Transistors
Venue: arXiv cs.ET 2016
Year: 2016

With many advantageous features, softness and better biocompatibility, flexible electronic devices have developed rapidly and increasingly attracted attention. Many currently applications with flexible devices are sensors and drivers, while there is nearly no utilization aiming at complex computation since flexible devices have lower electron mobility, simple structure and large process variation. In this paper, we proposed an innovative method that enabled flexible devices to implement real-time and energy-efficient Difference-of-Gaussian, which illustrated feasibility and potentials for them to achieve complicated real-time computation in future generation products.
Towards a DSL for Perception-Based Safety Systems
Venue: arXiv cs.RO 2016
Year: 2016

This paper is an extension to an early presented programming language, called a domain specific language. This paper extends the proposed concept with new sensors and behaviours to address real-life situations. The functionality was tested in lab experiments, and an extension to the earlier concepts is proposed.
On the Implicit Graph Conjecture
Venue: arXiv cs.CC 2016
Year: 2016

The implicit graph conjecture states that every sufficiently small, hereditary graph class has a labeling scheme with a polynomial-time computable label decoder. We approach this conjecture by investigating classes of label decoders defined in terms of complexity classes such as P and EXP. For instance, GP denotes the class of graph classes that have a labeling scheme with a polynomial-time computable label decoder. Until now it was not even known whether GP is a strict subset of GR. We show that this is indeed the case and reveal a strict hierarchy akin to classical complexity. We also show that classes such as GP can be characterized in terms of graph parameters. This could mean that certain algorithmic problems are feasible on every graph class in GP. Lastly, we define a more restrictive class of label decoders using first-order logic that already contains many natural graph classes such as forests and interval graphs. We give an alternative characterization of this class in terms of directed acyclic graphs. By showing that some small, hereditary graph class cannot be expressed with such label decoders a weaker form of the implicit graph conjecture could be disproven.
Linear Codes over Galois Ring $GR(p^2,r)$ Related to Gauss sums
Venue: arXiv cs.IT 2016
Year: 2016

Linear codes over finite rings become one of hot topics in coding theory after Hommons et al.([4], 1994) discovered that several remarkable nonlinear binary codes with some linear-like properties are the images of Gray map of linear codes over $Z_4$. In this paper we consider two series of linear codes $C(G)$ and $\widetilde{C}(G)$ over Galois ring $R=GR(p^2,r)$, where $G$ is a subgroup of $R^{(s)^*}$ and $R^{(s)}=GR(p^2,rs)$. We present a general formula on $N_β(a)$ in terms of Gauss sums on $R^{(s)}$ for each $a\in R$, where $N_β(a)$ is the number of a-component of the codeword $c_β\in C(G) (β\in R^{(s)})$ (Theorem 3.1). We have determined the complete Hamming weight distribution of $C(G)$ and the minimum Hamming distance of $\widetilde{C}(G)$ for some special G (Theorem 3.3 and 3.4). We show a general formula on homogeneous weight of codewords in $C(G)$ and $\widetilde{C}(G)$ (Theorem 4.5) for the special $G$ given in Theorem 3.4. Finally we obtained series of nonlinear codes over $\mathbb{F}_{q} \ (q=p^r)$ with two Hamming distance by using Gray map (Corollary 4.6).
Complete Elgot Monads and Coalgebraic Resumptions
Venue: arXiv cs.LO 2016
Year: 2016

Monads are extensively used nowadays to abstractly model a wide range of computational effects such as nondeterminism, statefulness, and exceptions. It turns out that equipping a monad with a (uniform) iteration operator satisfying a set of natural axioms allows for modelling iterative computations just as abstractly. The emerging monads are called complete Elgot monads. It has been shown recently that extending complete Elgot monads with free effects (e.g. operations of sending/receiving messages over channels) canonically leads to generalized coalgebraic resumption monads, previously used as semantic domains for non-wellfounded guarded processes. In this paper, we continue the study of the relationship between abstract complete Elgot monads and those that capture coalgebraic resumptions, by comparing the corresponding categories of (Eilenberg-Moore) algebras. To this end we first provide a characterization of the latter category; even more generally, we formulate this characterization in terms of Uustalu's parametrized monads. This is further used for establishing a characterization of complete Elgot monads as precisely those monads whose algebras are coherently equipped with the structure of algebras of coalgebraic resumption monads.
Who are Like-minded: Mining User Interest Similarity in Online Social Networks
Venue: arXiv cs.SI 2016
Year: 2016

In this paper, we mine and learn to predict how similar a pair of users' interests towards videos are, based on demographic (age, gender and location) and social (friendship, interaction and group membership) information of these users. We use the video access patterns of active users as ground truth (a form of benchmark). We adopt tag-based user profiling to establish this ground truth, and justify why it is used instead of video-based methods, or many latent topic models such as LDA and Collaborative Filtering approaches. We then show the effectiveness of the different demographic and social features, and their combinations and derivatives, in predicting user interest similarity, based on different machine-learning methods for combining multiple features. We propose a hybrid tree-encoded linear model for combining the features, and show that it out-performs other linear and treebased models. Our methods can be used to predict user interest similarity when the ground-truth is not available, e.g. for new users, or inactive users whose interests may have changed from old access data, and is useful for video recommendation. Our study is based on a rich dataset from Tencent, a popular service provider of social networks, video services, and various other services in China.
Elastic Functional Coding of Riemannian Trajectories
Venue: arXiv cs.CV 2016
Year: 2016

Visual observations of dynamic phenomena, such as human actions, are often represented as sequences of smoothly-varying features . In cases where the feature spaces can be structured as Riemannian manifolds, the corresponding representations become trajectories on manifolds. Analysis of these trajectories is challenging due to non-linearity of underlying spaces and high-dimensionality of trajectories. In vision problems, given the nature of physical systems involved, these phenomena are better characterized on a low-dimensional manifold compared to the space of Riemannian trajectories. For instance, if one does not impose physical constraints of the human body, in data involving human action analysis, the resulting representation space will have highly redundant features. Learning an effective, low-dimensional embedding for action representations will have a huge impact in the areas of search and retrieval, visualization, learning, and recognition. The difficulty lies in inherent non-linearity of the domain and temporal variability of actions that can distort any traditional metric between trajectories. To overcome these issues, we use the framework based on transported square-root velocity fields (TSRVF); this framework has several desirable properties, including a rate-invariant metric and vector space representations. We propose to learn an embedding such that each action trajectory is mapped to a single point in a low-dimensional Euclidean space, and the trajectories that differ only in temporal rates map to the same point. We utilize the TSRVF representation, and accompanying statistical summaries of Riemannian trajectories, to extend existing coding methods such as PCA, KSVD and Label Consistent KSVD to Riemannian trajectories or more generally to Riemannian functions.
Leveraging MPI-3 Shared-Memory Extensions for Efficient PGAS Runtime Systems
Venue: arXiv cs.DC 2016
Year: 2016

The relaxed semantics and rich functionality of one-sided communication primitives of MPI-3 makes MPI an attractive candidate for the implementation of PGAS models. However, the performance of such implementation suffers from the fact, that current MPI RMA implementations typically have a large overhead when source and target of a communication request share a common, local physical memory. In this paper, we present an optimized PGAS-like runtime system which uses the new MPI-3 shared-memory extensions to serve intra-node communication requests and MPI-3 one-sided communication primitives to serve inter-node communication requests. The performance of our runtime system is evaluated on a Cray XC40 system through low-level communication benchmarks, a random-access benchmark and a stencil kernel. The results of the experiments demonstrate that the performance of our hybrid runtime system matches the performance of low-level RMA libraries for intra-node transfers, and that of MPI-3 for inter-node transfers.
The Design Principles of Konrad Zuse's Mechanical Computers
Venue: arXiv cs.OH 2016
Year: 2016

Konrad Zuse built the Z1, a mechanical programmable computing machine, between 1935/36 and 1937/38. The Z1 was a binary floating-point computing device. The individual logical gates were constructed using metallic plates and interconnection rods. This paper describes the design principles Zuse followed in order to complete a complex calculating machine, as the Z1 was. Zuse called his basic switching elements "mechanical relays" in analogy to the electrical relays used in telephony.
Robust static output feedback control using a Particle Swarm Optimization-DE-linear matrix inequality algorithm hybrid algorithm
Venue: arXiv cs.SY 2016
Year: 2016

Under the multi-objective framework, this paper presents a hybrid algorithm to solve robust static output feedback control problem for continuous poly-topic uncertain system. To obtain static output feedback gain, a new hybrid algorithm is proposed by combination of a hybrid algorithm of the Particle Swarm Optimization and Differential Evolution (DE), and the linear matrix inequality method. The proposed algorithm is used to solve a optimization problem with a bi-linear matrix inequality constraints. The Particle Swarm Optimization-DE hybrid algorithm was used to obtain a population of controllers, and linear matrix inequality approach was used to optimize a performance criterion of the system. Taking a hybrid H 2/H infinite control problem as example, the detailed algorithm is presented to solve robust static output feedback control problem. The simulation results show that the proposed hybrid algorithm improves the convergence rate and accuracy of iterative methods and the original DE-linear matrix inequality algorithm.
Exponential stability of a PI plus reset integrator controller by a sampled-data system approach
Venue: arXiv cs.SY 2016
Year: 2016

The paper deals with the stability analysis of time-delay reset control systems, for which the resetting law is assumed to satisfy a time-dependent condition. A stability analysis of the closed-loop system is performed based on an appropriate sampled-data system. New linear matrix inequality (LMI) conditions are proposed to ensure the exponential stability of the closed-loop resulting of the connection of a plant with a proportional and integral controller together with a reset integrator (PI+RI).
The Exploratory Research of the Effect Communication Model and Effect Improving Strategy of Interactive Advertising
Venue: arXiv cs.CY 2016
Year: 2016

Interactive advertising which characterized by interactivity has become the mainstream of advertising by gradually replacing traditional one-way advertising during the new media era. This paper has obeyed the research outline below, literature review, background description, assumption proposed, and empirical analysis. Therefore, this paper proposed the communication model of interactive advertising and drawn two related important conclusions, interactivity has brought positive effect to advertising communication, different type of consumers tend to use different interactive options in different ways. Furthermore, this paper also presented three related optimization strategies to improving the communication of interactive advertising, namely, 1.changing communication model from one-way to two-way, 2.renovating new communication process and effect-generated path, 3.renovating new strategy portfolio to improving the communication effect of interactive advertising.
Testing fine-grained parallelism for the ADMM on a factor-graph
Venue: arXiv cs.DC 2016
Year: 2016

There is an ongoing effort to develop tools that apply distributed computational resources to tackle large problems or reduce the time to solve them. In this context, the Alternating Direction Method of Multipliers (ADMM) arises as a method that can exploit distributed resources like the dual ascent method and has the robustness and improved convergence of the augmented Lagrangian method. Traditional approaches to accelerate the ADMM using multiple cores are problem-specific and often require multi-core programming. By contrast, we propose a problem-independent scheme of accelerating the ADMM that does not require the user to write any parallel code. We show that this scheme, an interpretation of the ADMM as a message-passing algorithm on a factor-graph, can automatically exploit fine-grained parallelism both in GPUs and shared-memory multi-core computers and achieves significant speedup in such diverse application domains as combinatorial optimization, machine learning, and optimal control. Specifically, we obtain 10-18x speedup using a GPU, and 5-9x using multiple CPU cores, over a serial, optimized C-version of the ADMM, which is similar to the typical speedup reported for existing GPU-accelerated libraries, including cuFFT (19x), cuBLAS (17x), and cuRAND (8x).
Sums of read-once formulas: How many summands suffice?
Venue: arXiv cs.CC 2016
Year: 2016

An arithmetic read-once formula (ROF) is a formula (circuit of fan-out 1) over $+,\times$ where each variable labels at most one leaf. Every multilinear polynomial can be expressed as the sum of ROFs. In this work, we prove, for certain multilinear polynomials, a tight lower bound on the number of summands in such an expression.