- talks - lists.cs.princeton.edu

Distinguished Colloquium Speaker Wed. March 10- Barbara Liskov
by Nicole E. Wagenblast 08 Mar '10

08 Mar '10

The Power of Abstraction Barbara Liskov Wednesday, March 10- 4:30pm Friend Convocation Room Abstraction is at the center of much work in Computer Science. It encompasses finding the right interface for a system as well as finding an effective design for a system implementation. Furthermore, abstraction is the basis for program construction, allowing programs to be built in a modular fashion. This talk will discuss how the abstraction mechanisms we use today came to be, how they are supported in programming languages, and some possible areas for future research.

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Colloquium Speaker, Mon. March 8, 2010- Ranjit Jhala
by Nicole E. Wagenblast 04 Mar '10

04 Mar '10

Algorithmic Software Verification Ranjit Jhala, University of California, San Diego Monday, March 8, 2010- 4:30pm Small Auditorium, CS 105 Software is everywhere, and yet, extremely unreliable. One key to reliability is the design of cost-effective techniques whereby developers can formally specify essential properties of their code, and, machines can rigorously verify that the properties hold, or demonstrate corner cases where they fail. In this talk, we describe two such techniques. First, a scheme that uses logical predicates and theorem provers to automatically compute safety proofs. Second, an approach that uses random walks to find liveness bugs in distributed systems. We describe the key algorithms underlying these approaches and the resulting tools that have helped verify and find subtle defects in a variety of complex software.

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Today's Colloquium moved to CS104
by Nicole E. Wagenblast 03 Mar '10

03 Mar '10

Today's Colloquium moved to the Large Auditorium CS104 Behind the Scenes at Pixar Rob Cook, Pixar Today- 4:30pm LARGE Auditorium CS 104 This talk takes you behind the scenes at Pixar Animation Studios for a look at how its 3D computer graphics films are made. The process starts with the development of the story and continues with modeling the geometry, animating the characters, simulating things like water and cloth and hair, defining the look of the surfaces, putting lights in the scene, and rendering the images. Making a computer animated film requires a close collaboration between artists and technical experts in many areas of expertise and is a great example of the value of bringing different disciplines together. Rob was the co-architect and primary author of RenderMan, software that creates photo-realistic computer images. Every film nominated for a Visual Effects Oscar in the last 15 years has used RenderMan. In 2001, along with two colleagues, Rob received an Oscar for his contributions, the first ever given for software. He has also received the Steven A. Coons Award for lifetime achievement in computer graphics and was inducted into the National Academy of Engineering. Rob has a Bachelor's degree in Physics from Duke University and a Master's in Computer Graphics from Cornell University. At Cornell, he worked on simulating realistic surfaces, taking computer-generated images beyond the distinctive plastic look they had at the time. In 1981, he joined Lucasfilm / Pixar, where he developed the first programmable shader, which is now an essential part of GPUs and game engines. He was the first to use Monte Carlo techniques in computer graphics, which was essential for the simulation of complex, realistic lights and camera effects. The latter proved particularly important in the special effects industry, because it allowed computer-generated imagery to match the motion blur and depth of field of the live-action footage with which it was combined. He is currently the Vice President of Advanced Technology at Pixar.

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Distinguished Colloquium Speaker Wed. March 3- Rob Cook
by Nicole E. Wagenblast 01 Mar '10

01 Mar '10

Behind the Scenes at Pixar Rob Cook, Pixar 4:30pm Small Auditorium CS 105 This talk takes you behind the scenes at Pixar Animation Studios for a look at how its 3D computer graphics films are made. The process starts with the development of the story and continues with modeling the geometry, animating the characters, simulating things like water and cloth and hair, defining the look of the surfaces, putting lights in the scene, and rendering the images. Making a computer animated film requires a close collaboration between artists and technical experts in many areas of expertise and is a great example of the value of bringing different disciplines together. Rob was the co-architect and primary author of RenderMan, software that creates photo-realistic computer images. Every film nominated for a Visual Effects Oscar in the last 15 years has used RenderMan. In 2001, along with two colleagues, Rob received an Oscar for his contributions, the first ever given for software. He has also received the Steven A. Coons Award for lifetime achievement in computer graphics and was inducted into the National Academy of Engineering. Rob has a Bachelor's degree in Physics from Duke University and a Master's in Computer Graphics from Cornell University. At Cornell, he worked on simulating realistic surfaces, taking computer-generated images beyond the distinctive plastic look they had at the time. In 1981, he joined Lucasfilm / Pixar, where he developed the first programmable shader, which is now an essential part of GPUs and game engines. He was the first to use Monte Carlo techniques in computer graphics, which was essential for the simulation of complex, realistic lights and camera effects. The latter proved particularly important in the special effects industry, because it allowed computer-generated imagery to match the motion blur and depth of field of the live-action footage with which it was combined. He is currently the Vice President of Advanced Technology at Pixar.

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Colloquium Speaker Monday, March 1- Eran Tromer
by Nicole E. Wagenblast 25 Feb '10

25 Feb '10

Side Channels and their Mitigation in Cloud Computing Security Eran Tromer, MIT 4:30pm Small Auditorium CS 105 Today's computers run numerous processes of different sensitivity and trustworthiness, and often the only boundary between a hostile network and sensitive data relies on flimsy confinement assumptions. The platform purports to protect processes from each other, but side channels arise from lower architectural layers, such as contention for shared hardware resources, and create inadvertent cross-talk. For example, we have shown how observing contention for the CPU cache allows an attacker to steal other users' encryption keys in a few milliseconds. Confinement violations are especially grievous in the context of cloud computing ("infrastructure as a service"), where users acquire computational capacity in the form of virtual machines running on a service provider's shared hardware pool. Cross-talk between mutually-untrusting virtual machines running on the same hardware creates the risk of information exfiltration across machines and between users, as we have demonstrated on Amazon EC2. These security vulnerabilities raise the challenge of achieving trustworthy computation on leaky platforms. We discuss potential solutions, including a new work on mitigating side channels using just-in-time dynamic transformation of x86 machine code. This talk includes joint works with Saman Amarasinghe, Dag Arne Osvik, Thomas Ristenpart, Ron Rivest, Stephan Savage, Hovav Shacham, Adi Shamir and Qin Zhao.

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D Steurer preFPO
by Melissa Lawson 24 Feb '10

24 Feb '10

David Steurer will present his preFPO on Monday March 1 at 3PM in Room 402. The members of his committee are: Sanjeev Arora, advisor; Russell Impagliazzo (IAS), Boaz Barak, Moses Charikar, and Bernard Chazelle. Everyone is invited to attend his talk. His abstract follows below. ----------------------------------------------------------- On Strengths and Limits of Relaxations for Combinatorial Optimization Mathematical programming relaxations are powerful tools for solving or approximating combinatorial optimization problems. This thesis explores the strengths and limits of these tools for a selection of basic optimization problems. A central open question in this context is the Unique Games Conjecture (Khot 2002), which asserts that a certain optimization problem, called Unique Games, is hard to approximate in a certain regime. In recent years, a sequence of works established that this conjecture has profound implications: If the conjecture is true, then a certain semidefinite relaxations, called Basic-SDP, is optimal for a large range of optimization problems, in the sense that no efficient relaxation can achieve a better approximation for any of these problems. We make the following contributions towards a better understanding of the Unique Games Conjecture and semidefinite relaxations of combinatorial optimization problems: - We exhibit an optimal rounding scheme for constraint satisfaction problems (CSPs), a well-studied class of combinatorial optimization problem. The guarantee of the scheme matches the integrality gap of the Basic-SDP relaxation for every CSP. In contrast to many previous rounding algorithms, our scheme is generic and very simple. Moreover, it allows for a principled analysis. - Using our rounding scheme and a framework (Arora and Kale 2007) for solving semidefinite relaxations, we develop an approximation algorithm for CSPs whose approximation guarantee matches the integrality of the Basic-SDP relaxation and whose running time is quasi-linear. Assuming the Unique Games Conjecture, no polynomial time algorithm can have a better approximation guarantee. - We confirm the Unique Games Conjecture for a restricted model of computation given by a hierarchy of semidefinite relaxations. In particular, we show that for every CSP, the integrality gap of the Basic-SDP cannot be improved by adding a large class of valid inequalities. It was a long-standing open question whether such stronger relaxation could lead to better approximation algorithms for problems like Max-Cut or Multiway-Cut. Our result answers this question in the negative. - Finally, we establish a connection between the Unique Games Conjecture and the problem of approximating the expansion profile of graphs. In particular, we show that the Unique Games Conjecture is true if the expansion of small sets in graphs is hard to approximate in a certain regime. This result provides the first non-trivial sufficient condition for the truth of the conjecture. (Previously, only implications of the truth of the conjecture were known.) Based on joint works with Prasad Raghavendra.

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Colloquium Speaker, Feb. 24, 2010- Edgar Berdahl
by Nicole E. Wagenblast 23 Feb '10

23 Feb '10

Physical Interfaces For Applications In Music Edgar Berdahl, Stanford University 4:30pm Small Auditorium CS 105 Since the 1960s at the latest, the computer has been capable of digitally synthesizing any perceivable sound. However, in a live context, human-computer interfaces limit the bandwidth and quality of the interaction between the performer and the sound synthesizer. This talk focuses on physical interfaces for music, which operate according to the laws of physics to seamlessly and intimately connect musicians with sound synthesizers. In particular, we study how to design interfaces that assist a performer in making musical gestures. For example, the haptic drum provides a performer's drumstick with an extra push every time that the performer strikes the drum. This device allows the performer to make gestures that would otherwise be very difficult or impossible, such as arbitrarily long one-handed drum rolls and arbitrarily complex rudiments. Next, we explain how to assist a performer in accurately selecting pitches from a continuous range on a Theremin-like haptic interface. We augment it with detents allowing the performer to feel the locations of equal-tempered pitches, yet the performer can still perform arbitrary pitch inflections such as glissandi, falls, and scoops. With the help of a subject test, we demonstrate that traditional detents as well as novel force-sensitive detents can provide accuracy improvements over simpler types of haptic feedback, such as spring feedback. In closing, we relate the work to research in robotics and mixed reality.

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Talk Friday, Feb 19: Jason Sanders of NVIDIA
by Nicole E. Wagenblast 19 Feb '10

19 Feb '10

Jason Sanders, NVIDIA Friday, February 19, 4:30 PM Small Auditorium (CS 105) Abstract: The computing industry is currently undergoing a parallel computing revolution. The era of upward-spiraling clock speeds has drawn to a close, and the era of increasing core counts is upon us. The graphics processing unit (GPU) features a massively parallel computing architecture and is well poised to figure heavily in this evolving landscape. Two programming interfaces for the GPU, CUDA C and OpenCL, are readily available. In this presentation, NVIDIA GPU architecture and its programming models are explored. Bio: Jason Sanders is currently a senior software engineer in the CUDA team. He has been at NVIDIA for over two years, where he has developed system software and most recently has completed a book on CUDA C, due to hit shelves in 2010. He received his BSE from Princeton University in 2001 and an MS from the University of California Berkeley in 2007.

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M Mahmoody Ghidary preFPO
by Melissa Lawson 19 Feb '10

19 Feb '10

Mohammad Mahmoody Ghidary will present his preFPO on Wednesday February 24 at 10:30AM in Room 402. The members of his committee are: Boaz Barak, advisor; Russell Impagliazzo (IAS/UCSD) and Moses Charikar, readers; Sanjeev Arora and Bernard Chazelle, nonreaders. Everyone is invited to attend his talk. His abstract follows below ------------------------------------------------------------ Title: Security vs Efficiency, NP-hard Primitives, and Unconditional Cryptography. Abstract: The questions that I have studied in my thesis can be divided into the following three categories: I) How efficient a (public key) cryptographic object can be while achieving a desired quantitative level of security? -We give tight lower-bounds on the efficiency of black-box constructions of two of the main public-key cryptographic objects from "random like functions": (1) public key encryption and (2) public key authentication (i.e. signature schemes). II) Since mathematical conjectures like P<>NP are necessary for the possibility of cryptography in the standard model of computation, can we build cryptographic primitives solely by assuming P <> NP, or do we need stronger assumptions? -For some cryptographic primitives such as collision resistant hash functions we prove that basing them on P<>NP through a black-box reduction has surprising implications about the prover complexity of proving co-NP. Also for the more general question of basing average-case hardness of NP on its worst-case hardness we present a connection to the question of whether SAT has program checkers. III) Which non-standard models offer us unconditional security, while being implementable in real life? -We study the possibility of achieving unconditionally secure protocols for the main cryptographic tasks in the model of stateless tokens of Katz. We present unconditionally secure commitment schemes and efficient zero-knowledge proof systems for NP which use only one token and fall into the much simpler model of "Interactive PCP" by Kalai-Raz. We also prove that unconditionally secure oblivious transfer is not possible in the full general form of the stateless token model.

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Fwd: Colloquium Speaker, Feb. 24, 2010- Edgar Berdahl
by Nicole E. Wagenblast 19 Feb '10

19 Feb '10

Physical Interfaces For Applications In Music Edgar Berdahl, Stanford University 4:30pm Small Auditorium CS 105 Since the 1960s at the latest, the computer has been capable of digitally synthesizing any perceivable sound. However, in a live context, human-computer interfaces limit the bandwidth and quality of the interaction between the performer and the sound synthesizer. This talk focuses on physical interfaces for music, which operate according to the laws of physics to seamlessly and intimately connect musicians with sound synthesizers. In particular, we study how to design interfaces that assist a performer in making musical gestures. For example, the haptic drum provides a performer's drumstick with an extra push every time that the performer strikes the drum. This device allows the performer to make gestures that would otherwise be very difficult or impossible, such as arbitrarily long one-handed drum rolls and arbitrarily complex rudiments. Next, we explain how to assist a performer in accurately selecting pitches from a continuous range on a Theremin-like haptic interface. We augment it with detents allowing the performer to feel the locations of equal-tempered pitches, yet the performer can still perform arbitrary pitch inflections such as glissandi, falls, and scoops. With the help of a subject test, we demonstrate that traditional detents as well as novel force-sensitive detents can provide accuracy improvements over simpler types of haptic feedback, such as spring feedback. In closing, we relate the work to research in robotics and mixed reality.

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