The Taub Faculty of Computer Science Events and Talks

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Modern software employs dynamic memory allocation to support its memory needs. Allocation and de-allocation of memory create fragmentation: holes between the allocated objects in the memory may be too small to further satisfy future allocation. Fragmentation complicates memory allocation. Furthermore, fragmentation creates a space overhead sometimes making a program crash even though enough memory for allocation is available. Compaction defragments the memory by compacting all obj...
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Tandem mass spectrometry (MS/MS) has emerged as the tool of choice for high-throughput proteomics analysis. In a typical MS/MS experiment, a protein mixture sample is digested to peptides and is chromatographically separated. Homogenous sets of peptide molecules are then selected by the mass spectrometer and fragmented via collision induced dissociation. The outcome of this process is recorded as a mass spectrum, which is a list of fragment masses and their corresponding int...
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Let F be the finite field of q elements. An (n,k)-affine extractor is a coloring of F^n with 2 colors, such that every affine subspace of dimension at least k in F^n is colored in a balanced way. Roughly speaking, the problem of explicitly constructing affine extractors gets harder as the field size q gets smaller and easier as k gets larger. In this work, we construct affine extractors whenever q = \Omega( (n/k)^2), provided that F has characteristic \Omega(n/k). For ...
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We present Video SnapCut, a robust video object cutout system that significantly advances the state-of-the-art. In our system segmentation is achieved by the collaboration of a set of local classifiers, each adaptively integrating multiple local image features. We show how this segmentation paradigm naturally supports local user editing and propagates them across time. The object cutout system is completed with a novel coherent video matting technique. A comprehensive evaluation a...
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Fitting an algebraic equation to observed data is one of the first steps of many computer vision applications. For example, we fit lines and curves to points in 2D and planes and surfaces in 3D. Computing computing the fundamental matrix or the homography matrix can also be viewed as fitting in a high-dimensional space. A naive way for this is the least squares, also known as ``algebraic distance minimization'', minimizing the sum of squares of terms that should b...
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If D is a countable set of positive reals, let X_n(D) be the following graph: the vertices are the points of the n-dimensional Euclidean space, two points joined if their distance is in D. We determine the list-chromatic number of these graphs as much as possible...
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We introduce a new geometric definition of affine combinations of two compact subsets of R^n. The 4-point interpolatory subdivision schemes for points is adapted to sets, by first expressing the insertion rule in terms of repeated binary averages, and then replacing these affine combinations of pairs of points by the new affine combinations of sets. This subdivision scheme is applied to the reconstruction of multidimensional objects from cross-sections....
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Server virtualization has been widely adopted by the market, and the number of servers running virtual machines is increasing daily. As machine virtualization gains popularity, the hypervisor itself, along with its management stack, becomes a basic and required part of the system. The next natural evolution phase in the virtualization abstraction chain is to view the hypervisor as part of the user workload, and to be able to run multiple hypervisors inside virtual machines, each w...
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Biological systems are complex, involving feedbacks across numerous processes, mechanisms and objects. Experimental analysis, by its nature, rarely captures the behavior of the complete biological system as it divides the system into static interactions with reduced spatial dimensionality and minimal dynamics. To bridge the gap between experimental findings and the underlying system behavior, we formalize biological findings into mathematically and algorithmically rigorous specifi...
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In learning with privileged information (Vapnik, 2006) the labeled training examples have two views, primary and secondary, and the test examples have only a primary view. The goal of the learner is to leverage the information from these two views in order to build an accurate classifier in the primary view. SVM+ algorithm, introduced by Vapnik, is a major tool for learning with privileged information. Recently Vapnik, Vashist and Pavlovich (2009) showed that by utilizi...
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Comparative study of real-time graphics architectures The graphics industry is undergoing dramatic changes. A variety of new graphics pipeline topologies are now emerging, converging between GPUs and multicore-based graphics processors, both leaning on high parallelism and increasing flexibility. The GPUs, based on hardware graphics pipeline, are becoming more flexible by increased programmability, precision and performance, having improved load balance by hundreds of unified shad...
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Aviv Sharon is a contributor to the game, mainly in the graphics area. In addition to the presentation of the game, we hope to establish a reasonably-fast IRC chat with a group of the leading developers of 0AD, on: #0ad on QuakeNet. The purpose of the chat is to refer questions to the leading developers. You are all invited to lurk on the channel, even if you miss the talk... ...
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We describe a new part based detection algorithm. The proposed algorithm uses an empirical model, based on data extracted from the test image to bound the probability that a model candidate arises from a noncategory-related image. The decision is adaptive and does not rely on parameters optimized for possibly unrelated non-category images. Finally, the decision process provides an bound on the number of false alarms in the image. We explain the a-contrario method, deriv...
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The famous Hall's marriage theorem from 1935 states that in a bipartite graph with sides M and W, there is a matching of M into W if and only if every subset A of M has at least |A| neighbors in W. A generalization of this theorem for r-partite hypergraphs was proved by Aharoni and Haxell in 2000, using topological methods. In 2005 Aharoni, Berger and Meshulam proved a stronger version of this theorem, using a new function on graphs, called the Gamma function. This function ...
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The well known learning models in Computational Learning Theory are either adversarial, meaning that the examples are arbitrarily selected by the teacher, or i.i.d., meaning that the teacher generates the examples independently and identically according to a certain distribution. However, it is also quite natural to study learning models in which the teacher generates the examples according to a stochastic process. A particularly simple and natural time-driven process is the rand...
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In this talk, I will talk about a new invariance principle for polytopes (intersection of halfspaces) and some applications of the same. Invariance Principle: Let X be randomly chosen from {−1,1}^n, and let Y be randomly chosen from a spherical Gaussian on R^n. For any polytope P formed by the intersection of k halfspaces, |Pr[X∈P]−Pr[Y∈P]|≤polylog(k)·∆, where ∆ is a parameter that is small for “regular” polytopes. A polytope is said to be regul...
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Full reference image Quality Index (QI) is an important tool for a cheap and fast assessment of image degradation by different algorithms. A short survey and comparison of recent gray-scale and color image QI is presented. We choose to divide degradation of images into two: luminance changes and saturation changes. From the comparison we see that, in the case of luminance changes, gray scale QI better correlates with Human Visual System (HVS) test results. On the other hand ...
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Images taken through a medium may suffer from poor visibility and loss of contrast. Light passing through undergoes absorption and scattering. Wavelength dependent attenuation causes changes in color and brightness. In addition, light that is scattered back from the medium into the camera (backscatter) veils the object, degrading visibility and contrast. Low signal to noise ratio imposes resolution limits, even if there is no blur. Moreover, refraction between the medium an...
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Compressive sensing is a relatively new theory that is based on the fact that many natural signals (or images) can be sparsely represented in some basis. The theory of compressive imaging is applied to directly capture a compressed version of an object's image. Here, we give an overview of different CI techniques, and focus on two that were developed in our group. While implementing conventional CS for imaging we have encountered some practical implement...
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Almost a year ago, Larry Guth and Nets Hawk Katz have obtained the tight upper bound $O(n^{3/2})$ on the number of joints in a set of $n$ lines in 3-space, where a joint is a point incident to at least three non-coplanar lines, thus closing the lid on a problem that has been open for nearly 20 years. While this in itself is a significant development, the groundbreaking nature of their work is the proof technique, which uses fairly simple tools from algebraic geometry, a tot...
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One of the principal goals of Computer Vision is to build artificial systems that are able to perceive and understand the world, obtaining information from images acquired by one or more cameras. The same objective, extended to generic sensors, can be found in Robotics, where autonomous robots require a complete knowledge of the environment to provide services and perform tasks as planning, obstacles avoidance or objects grasping. During this talk I will present a novel approach f...
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In general, I will be sharing my discovery with you: When the debugging of modern software is required, basic GDB techniques are insufficient, but new techniques can be created from the nearly 160 commands available in GDB. "Modern software" refers to multi- threading, using STL and other libraries, IPC, signals and exception mechanisms. In this lecture, I will explain techniques for debugging large, modern software written in C++. The presentation will be accompanied ...
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The ASPP family proteins have a key role in apoptosis regulation. ASPP1 and ASPP2 promote, while iASPP inhibits p53 mediated apoptosis. ASPP stands for _A_poptosis _S_timulating_P_rotein of _ p_53, as well as representing the domain constitution: _A_nkyrin repeats, _S_H3 and _P_roline rich containing _P_rotein. The ankyrin repeats and SH3 domains (Ank-SH3) mediate the interactions of the ASPP family members with major apoptosis regulators, including p53, Bcl-2 and NFκB....
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This work uses static data and control flow code analysis to aid in proving properties of systems with aspects. Some new categories of aspect advices (code segments) and introduced methods are defined, beyond the existing ones. The categories are chosen considering their effectiveness, in that they both provide real aid in verification of properties, and are automatically detectable using data and control flow. The theoretical part of the thesis investigates which linear t...
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Why do we need a cross-platform toolkit The qmake build system Strings, list + iterators in Qt4 signals+slots Basic GUI building The purpose of the lecture is not to teach Qt4, but to explain what is available in Qt4 and motivate you to sit on your behind and learn it. ...
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Nikolay Skarbnik Department of Electrical Engineering The Technion Abstract: Signal's phase is a non-trivial quantity. It is therefore often ignored in favor of signal's magnitude. However, phase conveys more information regarding signal structure than magnitude does, especially in the case of images. It is therefore essential to use phase information in various signal/image processing schemes as well as in computer vision. This is true for global phase and, even more so, for loca...
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We explain the "what", "who" and "how" of the Free Software Foundation GPL Compliance Lab. We go through five sample questions based on real questions the lab received and discuss their answers. We finish with a few words about GPL violations. The lecture is intended for the general audience interested in free software licensing and in particular the licenses published by the FSF. ...
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We present a method for automatic surface comparison and alignment based on principles from conformal geometry and optimal mass transportation. One application of the method is efficient calculation of point correspondences between surfaces. Another application is a novel distance definition between disc-type surfaces which forms a tractable alternative to the Gromov-Hausdorff distance. Joint work with I. Daubechies and T. Funkhouser. ...
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Graph isomorphism is an important problem and has received lot of attention over several years. Its complexity is still open. There have been polynomial-time algorithms for several subclasses of graphs, including planar graphs. For isomorphism of some of these graph classes, the focus has been on determining the parallel complexity. The goal has been to show the isomorphism problem for various graph classes to be complete for some natural complexity class. For pla...
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We will focus in this lecture about Linux Kernel sockets. Specifically, we will deal with the implementation the following sockets in the Linux kernel: UDP socket. Raw sockets. Unix Domain sockets. Netlink sockets. We will describe the mechanism of sending and receiveing packets with these types of kernel sockets, demonstrating it with short user space applications. We will also deal with Control Messages (aka "ancillary data") and demonstrate...
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Relief Analysis and Extraction We present an approach for extracting relieves and details from relief surfaces. We consider a relief surface as a surface composed of two components: a base surface and a height function which is defined over this base. However, since the base surface is unknown, the decoupling of these components is a challenge. We show how to estimate a robust height function over the base, without explicitly extracting the base surface. This height func...
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As far as protein-coding genes are concerned, there is a non-zero probability that at least one of the five possible overlapping sequences of any gene will contain an open-reading frame (ORF) of a length that may be suitable for coding a functional protein. It is, however, very difficult to determine whether or not such an ORF is functional. We developed a new method that employs evolutionary principles to identify functional overlapping genes based on the signat...
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We will deal in this lecture with Mesh networking, kernel sockets, netlink/rtnelink sockets and transport layer sockets. ...
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Tracking humans, understanding their actions and interpreting them are crucial to a great variety of applications. Tracking is used in automated surveillance, human-computer interface applications and in security applications. During the last decade extended research has been conducted on this subject. Analysis of human interactions is a complicated and challenging task for several reasons. First, the large number of body parts makes it hard to detect each part separately. Second,...
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Tracking humans, understanding their actions and interpreting them are crucial to a great variety of applications. Tracking is used in automated surveillance, human-computer interface applications and in security applications. During the last decade extended research has been conducted on this subject. Analysis of human interactions is a complicated and challenging task for several reasons. First, the large number of body parts makes it hard to detect each part separately. Second,...
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Tracking humans, understanding their actions and interpreting them are crucial to a great variety of applications. Tracking is used in automated surveillance, human-computer interface applications and in security applications. During the last decade extended research has been conducted on this subject. Analysis of human interactions is a complicated and challenging task for several reasons. First, the large number of body parts makes it hard to detect each part separately. Second,...
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Tracking humans, understanding their actions and interpreting them are crucial to a great variety of applications. Tracking is used in automated surveillance, human-computer interface applications and in security applications. During the last decade extended research has been conducted on this subject. Analysis of human interactions is a complicated and challenging task for several reasons. First, the large number of body parts makes it hard to detect each part separately. Second,...
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Tracking humans, understanding their actions and interpreting them are crucial to a great variety of applications. Tracking is used in automated surveillance, human-computer interface applications and in security applications. During the last decade extended research has been conducted on this subject. Analysis of human interactions is a complicated and challenging task for several reasons. First, the large number of body parts makes it hard to detect each part separately. Second,...
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This lecture is an overview of developing applications for Google's Android. We start by introducing Android and its components, we look at the anatomy of an Android application, we show the basic components of Android application development including UI design and finally we say some things about the development environment. The lecture is for people with no prior knowledge of the Android system as it is only an overview. ...
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Cell-to-cell and temporal variations in the concentrations of biomolecular components are inevitable. These variations in turn propagate along networks of chemical reactions to impart changes in the concentrations of still other species, such as phosphorylated transcription factors, that influence biological activity. Because excessive variations in the levels of certain active molecules might sometimes be deleterious to cell function, regulation systems have evolved that act to m...
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In this talk we will discuss the SLIC project developed at the University of Arizona and IBM Almaden Research center. The SLIC (Semantically Linked Instructional Content ) aims to assist students and scholars efficiently browse and seek segments of interest in educational videos of lectures and talks. In particular, it focuses on lectures that use slides, where the content of the slides file gives valuable hints as to how to break the video into meaningful parts (segments), and ho...
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KSM is a linux driver that allows dynamically sharing identical memory pages between one or more processes. Unlike traditional page sharing that is made at the allocation of the memory, ksm do it dynamically after the memory was created. Memory is periodically scanned; identical pages are identified and merged. The sharing is unnoticeable by the process that use this memory. (the shared pages are marked as readonly, and in case of write do_wp_page() take care to create new ...
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Say we place m balls sequentially into n bins, where each ball is placed by randomly selecting d bins and placing it in the least loaded of them. What is the load of the maximum bin when m>>n? It is well known that when d=1 the maximum load is m/n + \tildeO(sqrt(m/n)), whereas when d>=2 the maximum load is m/n + loglog n. Thus when more than one bin is sampled, the gap between maximum and average does not increase with the number of balls. We investigate a larger famil...
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One goal of Artificial Intelligence is to enable the creation of robust, fully autonomous agents that can coexist with us in the real world. Such agents will need to be able to learn, both in order to correct and circumvent their inevitable imperfections, and to keep up with a dynamically changing world. They will also need to be able to interact with one another, whether they share common goals, they pursue independent goals, or their goals are in direct conflict. This talk wi...
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Locally testable codes (LTCs) are error-correcting codes for which membership, in the code, of a given word can be tested by examining it in very few locations. Most known constructions of locally testable codes are linear codes, and give error-correcting codes whose duals have (superlinearly) {\em many} small weight codewords. Examining this feature appears to be one of the promising approaches to proving limitation results for (i.e., upper bounds on the rate of) LT...
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Compression of facial images using sparse and redundant representations and the K-SVD algorithm...
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Arduino is an open source hardware platform. Since its launch it became much more than just a hobbyist playground. This presentation will introduce the Arduino platform, go over some of the messy details and explore its potential to the casual hacker. No electric engineering background is needed, some basic C knowledge is assumed. ...
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Using ideas from automata theory we design a new efficient (deterministic) identity test for the noncommutative polynomial identity testing problem. More precisely, given as input a noncommutative circuit C computing a polynomial of degree d in the noncommutative ring F{x_1,x_2,...,x_n} with at most t monomials, where the variables x_i are noncommuting, we give a deterministic polynomial identity test that checks if C=0 and runs in time polynomial in d, n, size(C), an...
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In the affine rank minimization problem, the goal is to minimize the rank of a matrix subject to a set of affine constraints. This is in general an NP-hard problem. We study a convex relaxation of this problem where the rank objective function is replaced by the gamma_2 norm. The gamma_2 norm can be viewed as a weighted version of the trace norm and can be expressed as a semidefinite program. We show that, given certain conditions on the constraint matrices, if the...
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Let f_{1},f_{2}, f_{3} : F_2^n -> {0,1} be three Boolean functions. We say a triple (x,y,x+y) is a triangle in the function triple (f_{1}, f_{2}, f_{3}) if f_{1}(x)=f_{2 (y)=f_{3}(x+y)= 1. (f_{1}, f_{2}, f_{3}) is said to be triangle-free if there is no triangle among the three functions. The distance between a function triple and triangle-free functions is the minimum fraction of the function values one needs to modify in order to make the function triple triangle-fre...
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In this talk I describe several techniques that we developed to support the generation of high quality code for the Cell Broadband Engine, addressing some of its key challenges and advantages. The architecture of the Cell Broadband Engine developed jointly by Sony, Toshiba, and IBM, represents a new direction in processor design. In addition to a PowerPC-compatible Power Processor Element (PPE) the Cell architecture features an array of eight Synergistic Processor Elements...
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Geometric modeling deals with representing real objects in a virtual world. A popular geometric representation is the polygonal model. For many applications the need arises to improve the model while preserving its intrinsic geometric property, that it still describes the same "real" object. In this talk, we present a few applications, which although are quite different, use similar geometric concepts and mathematical machinery, the most noticeable being the notion of conformality...
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OpenCL is the first Cross-Architecture, Cross-OS, open standard for parallel computing on heterogeneous systems. It targets GPU's, CPU's, and other processing devices (like DSP's and Accelerators), providing a uniform programming model of the system. OpenCL is designed to support a wide range of usages, from GPGPU GFX usages (like Physics) to High Performance Computing. This introduction will present OpenCL Programming Model (platform, memory, compilation, etc.) & the OpenCL...
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Voronoi diagrams appear in many areas in science and technology and have diverse applications. Roughly speaking, they are a certain decomposition of a given space into cells, induced by a distance function and by a tuple of subsets called the generators or the sites. Voronoi diagrams have been the subject of extensive research during the last 35 years, and many algorithms for computing them have been published. However, these algorithms are for specific cases. They impose v...
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Collages have been a common form of artistic expression since their first appearance in China around 200 BC. Recently, with the advance of digital cameras and digital image editing tools, collages have gained popularity also as a summarization tool. We propose an approach for automating collage construction, which is based on assembling exact cutouts of salient regions in a puzzle-like manner. We show that this approach produces collages that are informative, compact, and eye-ple...
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gdb is one of the more powerful tools that you have as a programmer in the UNIX environment. This talk is an introduction to gdb and how to make it work for you. This is the second part of a 2-meetings set . In the 1st meeting we have covered everything up to the section titled 'Where Have My Source Files Gone?' in the slides. In the second meeting we'll go over the rest (writing gdb macros, debugging multi-threaded programs and debugging multi-process prog...
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An affine disperser over a field F for sources of dimension d is a function f: F^n -> F that is nonconstant (i.e., takes more than one value) on inputs coming from a d-dimensional affine subspace of F^n. Affine dispersers have been considered in the context of deterministic extraction of randomness from structured sources of imperfect randomness, and in particular, generalize the notion of dispersers for bit-fixing sources. Previously, explicit constructions ...
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Light sources and cameras are optical duals: sources emit light rays while the cameras capture them. This talk will argue that light sources can serve as better cameras in many applications, advancing the state of the art in computer vision. (a) By moving a light source instead of a camera, we show how to reconstruct highly intricate shapes like wreaths, corals and tree branches from hundreds of 'views'. (b) We leverage the 'illumination dithering' in the micromirror array of DLP ...
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Translation Efficiency (TE) is a basic process of favoring codons with higher levels of tRNAs. In this talk, I will survey three recent results that are related to studying TE from a computational/systems biological aspect: a) TE in humans is efficient: It is believed that in many unicellular organisms codon bias has evolved to optimize TE. Previous studies, however, have left the question of TE in humans an intriguingly open one. We perform the first large scale t...
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The widely held belief that BQP strictly contains BPP raises fundamental questions: Upcoming generations of quantum computers might already be too large to be simulated classically. Is it possible to experimentally test that these systems perform as they should, if we cannot efficiently compute predictions for their behavior? Vazirani has asked [Vaz07]: If computing predictions for Quantum Mechanics requires exponential resources, is Quantum Mechanics a falsifiable the...
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The widely held belief that BQP strictly contains BPP raises fundamental questions: Upcoming generations of quantum computers might already be too large to be simulated classically. Is it possible to experimentally test that these systems perform as they should, if we cannot efficiently compute predictions for their behavior? Vazirani has asked [Vaz07]: If computing predictions for Quantum Mechanics requires exponential resources, is Quantum Mechanics a falsifiable the...
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Bioinformatics Forum: It is well known that the string edit distance and the alignment of strings coincide, while the alignment of trees differs from the tree edit distance. In this talk, we recall various constraints on directed acyclic graphs that allow for a unique (up to isomorphism) representation, called the path multiplicity representation, and present a new method for the alignment of trees and directed acyclic graphs that exploits the path multiplicity representat...
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Comparative genomics and systems biology reveal several surprising universals of genome evolution such as the distribution of evolution rates across genes, the distribution of paralogous gene family size, and connections between expression and evolution rate. The existence of these universals calls for simple, general models of evolutionary processes akin to those used in statistical physics (eg, birth and death processes), and at least in some cases, such models seem to explain t...
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We derive a one-parameter local message-passing algorithm, called "norm-product", which covers both the tasks of computing approximate marginal probabilities and maximum a posteriori (MAP) assignment for general graphical models. A parameter $\epsilon$ controls a perturbation term of a "fractional entropy approximation" $\tilde H$ which includes Bethe, Tree-reweighted (TRW) and convex entropy approximations. When $\tilde H$ is the Bethe approximation, the settings $\epsilon=0$ and...
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OpenMp is a standard for shared memory parallelization of Fortran and c/c++. gcc 4.2 implements this standard in the gomp library. In the previous lecture we have reviewed some of the basic constructs. In this talk we will discuss the way to approach the task of using openMP in legacy code, and address some common implementation dilemmas the programmer is bound to hit. ...
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In a recent breakthrough, Moshkovitz and Raz [MR] proved that NP can be verified using two queries, sub-constant error, and nearly linear proof length. The main technical component of their result is a new composition theorem for certain specific 2-query PCPs. All earlier composition theorems suffered from incurring an additional query per composition. We abstract their proof and prove a generic 2-query PCP composition theorem with low error. More formally, we de...
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Fluorescent microscopy imaging has become one of the main tools of biological research. Most wet labs collect Gigabytes of images every day. The resulting data is almost exclusively annotated and analyzed by hand. Such data contains a wealth of information potentially relevant to a variety of research questions. Yet, due to the labor-intensive nature of data analysis and huge volume, the precious data is discarded without a chance to realize its full scientific value. A typical ...
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The Mean Shift procedure is a well established clustering technique that is widely used in imaging applications such as image and video segmentation, denoising, object tracking, texture classification, and others. However, the Mean Shift procedure has relatively high time complexity which is superlinear in the number of data points. In this paper we present a novel fast Mean Shift procedure which is based on the random sampling of the Kernel Density Estimate (KDE). We show theoret...
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Extracellular information received by plasma membrane receptors is encoded into complex temporal and spatial patterns of phosphorylation and topological relocation of signaling proteins. Integration of this information by protein kinase cascades creates the spatio-temporal code that confers signaling specificity and leads to important decisions that determine cell’s fate. Aberrant processing of signalling information is a leading cause of many human diseases that range from deve...
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Locally Decodable Codes (LDC) allow one to decode any particular symbol of the input message by making a constant number of queries to a codeword, even if a constant fraction of the codeword is damaged. In a recent work ~\cite{Yekhanin08} Yekhanin constructs a $3$-query LDC with sub-exponential length of size $\exp(\exp(O(\frac{\log n}{\log\log n})))$. However, this construction requires a conjecture that there are infinitely many Mersenne primes. In this paper we give the ...
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Translation validation is a technique for formally establishing the semantic equivalence of a source and a target of a code generator/compiler. In this work we present a translation validation tool for the Real-Time Workshop code generator that receives as input Simulink models and generates optimized C code. The lecture will begin with a demonstration of the Simulink models format and automatically generated C code. It will then focus on the verification condition that is ...
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Bioinformatics Forum: The reconstruction of evolutionary trees (also known as “phylogenies”) is central to many problems in Biology. With the massive amounts of molecular data being produced, attention has increasingly turned to phylogenetic analyses of larger datasets, containing several hundreds to several thousand nucleotide sequences. Accordingly, a new program, “Assembling the Tree of Life”, has set the goal of producing a highly accurate estimate of the evolutionary...
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The direct product code encodes the truth table of a function f:U-->R by a function f^k:U^k -->R^k, which lists the value of f in all k-tuples of inputs. We study its (approximate) proximity testing to this code in the "list decoding" regime. We give a 3-query tester for distance 1-exp(-k) (which is impossible with 2 queries). We also give a 2-query tester for distance 1-1/poly(k) for a derandomized version of this code (of polynomial rate). We then...
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LINUX EVENT: We will discuss the ways to promote the use in Linux among students and to improve the SSDL service. Prof. Yossi Gil will give a talk titled: "How to avoid in Linux programming". ...
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The common method of reconstructing a turbulence scene is through the creation of an artificial reference image. The reference image is usually obtained by averaging video through time. Using optical flow from that reference image to input images would give rise to such applications as: super-resolution, tracking and so forth. However this technique suffers from several drawbacks: the resulting artificial reference frame is blurred, so calculated optical-flow fields are not prec...
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This lecture is a sequel to the Linux Kernel Networking lecture, Advanced Linux Kernel Networking - Neighboring Subsystem; IPSec and IPv6 in the Linux Kernel (Advanced Linux Kernel Networking). - Short history of Linux Wireless : fullmac and softmac. - Wireless Modes of operation: infrastructure mode, independent mode (IBSS), and more. - The Linux Wireless stack (mac80211). - MLME (the management layer). - MLME operations: scanning, association....
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We consider the following question: given a two-argument boolean function $f$, represented as an $N\times N$ binary matrix, how hard is to determine the (deterministic) communication complexity of $f$? We address two aspects of this question. On the computational side, we prove that, under appropriate cryptographic assumptions (such as the intractability of factoring), the deterministic communication complexity of $f$ is hard to approximate to within some...
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We address the open engineering problem of blind separation of time/position varying mixtures. We show that there exists a large family of such mixtures that are separable without having prior information about the sources or the mixing system. Unlike studies concerned with instantaneous or convolutive mixtures, we relax the very-restrictive, widely-used, constraint of stationary in time and position, and deal with the more practical and difficult problem of a mixing syste...
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In this talk we present an algorithm that applies segment Voronoi diagrams and planar arrangements to the computation of the metric average of two simple polygons. The algorithm is relevant to approximation of set-valued functions. We describe the implementation of the algorithm and present a collection of computational examples. Based on the computational framework of the algorithm, the connectedness of the metric average of two simple polygons is studied. Finally, we exten...
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We show a connection between the semi-definite relaxation of unique games and their behavior under parallel repetition. Specifically, denoting by val(G) the value of a two-prover unique game G, and by sdpval(G) the value of a natural semi-definite program to approximate val(G), we prove that for every large enough $\ell$, if sdpval(G) is at least $1-\delta$, then the value of the $\ell$-times parallel repeated version of G is at least $sdpval(G)^{s \ell}$ where $s=O(\log(k...
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Stray light reflected by lens surfaces creates flare which affects the image. A pronounced form of this flare is aperture ghosting, where bright spots that resemble the shape of the lens aperture are overlayed on the image. This might disrupt image analysis. It occurs when a bright narrow source (usually the Sun) is in the vicinity of the field of view, though often the source may be outside the actual viewed field. This paper analyzes the geometry of this phenomenon. It theoretic...
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I'll give an overview of the Slashdot editorial process, and demonstrate the back-end tools (all running on Linux, mostly written in Perl, with an increasingly Ajax-based user interface) that we use to organize hundreds of submissions each day to select the handful that we post to the page. I'll also explain some of the software-based methods we use to identify and avoid abusive users, and answer any questions that I can. ...
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View-Dependent Texture Projection Mapping (VDTPM) is a technique used to render a photorealistic novel view of a scene based on a number of aerial photographs of the scene and an authentic 3D model of the scene. Unlike traditional texture mapping, where the texture is "pasted" on the 3D polygons, here the texture is placed on the object using texture projection. Texture projection is a technique which uses the camera model of the photograph to create a projective ...
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Distance based reconstruction methods of phylogenetic trees are split into two independent parts: first, inter-species distances are inferred using some stochastic model of sequence evolution; then the inferred distances are used to construct a tree. Most research in this area focuses on the second task. This talk concentrates on the task of inter-species distance estimation, and provides a general characterization of distance functions for stochastic substitution models. Then it ...
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We consider one-round games between a classical verifier and two provers who share entanglement. We show that when the constraints enforced by the verifier are `unique' constraints (i.e., permutations), the value of the game can be well approximated by a semidefinite program. Essentially the only algorithm known previously was for the special case of binary answers, as follows from the work of Tsirelson in 1980. Among other things, our result implies that the variant of th...
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Microsoft's End User License Agreement (EULA) allows customers to return unused copied of the Windows operation system to the manufacturer, for a refund or credit. Not surprisingly, the laptop manufacturers are not too happy with that, and they raise obstacles on customers who would like to get a refund. In this lecture I will talk about the first successful Windows Vista refund case in Israel. ...
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The classic Heilbronn's triangle problem is to maximize the area of the smallest of the $\binom{n}{3}$ triangles determined by $n$ points in the unit square. One aspect of the problem is finding the optimal locations of the points. Another issue is finding lower and upper bounds on the smallest triangle's area in the optimal configuration(s) of points. With respect to the first aspect, mathematicians and computer scientists have worked in the last decades to find good c...
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The Gowers uniformity norms U_k measure a certain kind of psuedo randomness. For example, a function f on a finite (large) dimensional vector space V over a finite field F has small U_2 norm if and only if all its Fourier coefficients are small - i.e it has no significant correlation with linear phase functions. The content of the inverse conjecture for the Gowers norms is that a similar relation exists between the U_k norms and polynomials of degree smaller th...
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There is a huge diversity of definitions of "visually meaningful" image segments, ranging from simple uniformly colored segments, textured segments, through symmetric patterns, and up to complex semantically meaningful objects. This diversity has led to a wide range of different approaches for image segmentation. We present a single unified framework for addressing this problem - "Segmentation by Composition". We define a good image segment as one which can be easily...
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Computing the Fourier transform is a basic building block used in numerous applications. For data intensive applications, even the O(N log N) running time of the Fast Fourier Transform (FFT) algorithm may be too slow, and sub-linear running time is necessary. Clearly, outputting the entire Fourier transform in sub-linear time is infeasible, nevertheless, in many applications it suffices to find only the \tau-significant Fourier transform coefficients, that is, the Four...
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The topology of metabolic networks may provide important insights not only into the metabolic capacity of species, but also into the habitats in which they evolved. In this talk I will present several analyses of metabolic networks and show how various ecological insights can be obtained from genomic-based data. I will first introduce various environmental and genetic factors that affect the structure of metabolic networks. I will then present the first large-scale co...
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Organizing images is crucial for dealing efficiently with large image collections. In this talk, I will explore approaches to such an organization and its benefits. I introduce a non-parametric Bayesian model called TAX (similar to NCRP), which can organize images into a tree-shaped taxonomy in an unsupervised manner. The main conclusions are: (a) images can be organized automatically, in a completely unsupervised manner; (b) this organization is intuitively appealin...
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Building hardware to run a Linux distro used to be quite tricky, involving plenty of trial and error with components while filing bug reports in various places. In the last year, hardware has reached the point where it is easier to build a Linux system that just works. Cathy Malmrose, a Linux hardware builder from Berkeley, California, US will share what she has learned from various OEMs and will give a broad view of how and where to get Linux-ready hardware. She will ...
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We consider private data analysis in the setting in which a trusted and trustworthy curator, having obtained a large data set containing private information, releases to the public a "sanitization'' of the data set that simultaneously protects the privacy of the individual contributors of data and offers utility to the data analyst. We focus on the case where the process is non-interactive; once the sanitization has been released the original data and the curator play no...
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In this talk I will introduce a new kind of attack (called Cube Attack) on cryptographic schemes which can be represented by an (unknown) low degree polynomial with tweakable public variables such as a plaintext or IV and fixed secret variables such as a key. Its complexity is exponential in the degree but only polynomial in the key size, and it was successfully applied to several concrete cryptographic schemes. The talk will be self contained, requiring no prior knowledg...
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