April 2012 - talks - lists.cs.princeton.edu

Dominic Kao MSE thesis talk
by Melissa M. Lawson 10 Apr '12

10 Apr '12

Dominic Kao will present his MSE thesis talk on Monday April 16 at 2PM in room 402. The members of his committee are: Yael Niv (PSY), her postdoc Carlos Diuk, and Adam Finkelstein, reader. Everyone is invited to attend his talk. His abstract follows below. --------------------- The world has already spent 5.93 million years playing the video game World of Warcraft. What makes video games rewarding? We suggest that one important factor in a player's enjoyment of a game is the schedule of rewards, specifically, we hypothesized that variable rewards are more interesting and enticing than a fixed reward size. To test this hypothesis we studied several variable reward schedules contrasted with a fixed reward schedule in a custom-built video game. We found that variable reward schedules were preferred, except when the schedule’s range included very small or non-existent (zero) rewards. Participants consistently mischaracterized the variable reward schedule as having a higher mean than the fixed schedule. We further hypothesized that reward schedule preference is an indicator for game genre preference. Ultimately, the conclusions made can be applied more broadly to the now ubiquitous game mechanics that surround us in both the real and virtual world.

1 0

J Huang preFPO
by Melissa M. Lawson 05 Apr '12

05 Apr '12

Jialu Huang will present her preFPO on Monday April 9 at 1PM in Room 301 (note room!!) The members of her committee are: David August, advisor; David Walker and Kai Li, readers; Doug Clark and JP Singh, nonreaders. Everyone is invited to attend her talk. Her abstract follows below. ========================================================================================= Abstract: Automatic parallelization is a promising approach to deliver scalable multi-threaded programs for multi-core architectures. Most existing techniques parallelize independent loops and insert global synchronizations at the end of each loop invocation. For programs with few loop invocations, these global synchronizations do not limit parallel execution performance. However, for programs with many loop invocations, those synchronizations can easily become the performance bottleneck since they frequently force all threads to wait, losing potential parallelization opportunities. Some automatic parallelization techniques apply static analyses to enable cross-invocation parallelization. Instead of waiting, threads can execute iterations from follow-up invocations if they do not cause any conflict. However, static analyses must be conservative, and therefore cannot handle programs with irregular dependence patterns. In order to enable more parallelization across loop invocations, this thesis presents two novel automatic parallelization techniques: BLISS and SBS. Unlike existing techniques relying on static analyses, these two techniques take advantage of runtime information to achieve much more aggressive parallelization. BLISS constructs a custom runtime engine which non-speculatively observes dependences at runtime and synchronizes iterations only when necessary; while SBS applies software speculative barriers to permit some of the threads to execute past the invocation boundaries. The two techniques are complimentary in the sense that they can parallelize programs with potentially very different characteristics. SBS is most effective when a program's cross-invocation dependences rarely cause a runtime conflict. BLISS' runtime engine imposes a marginal amount of overhead, but it also enables the technique to effectively parallelize programs whose dependences can cause frequent conflicts. Preliminary implementation and evaluation demonstrate that both techniques can achieve much better scalability compared to existing automatic parallelization techniques. ==============================================================================================

1 0

J Terrace preFPO
by Melissa M. Lawson 05 Apr '12

05 Apr '12

Jeff Terrace will present his preFPO on Thursday April 12 at 4PM in Room 302 (note room!). The members of his committee are: Michael Freedman, advisor; Adam Finkelstein and Phil Levis (Stanford), readers; Vivek Pai and Szymon Rusinkiewicz, nonreaders. Everyone is invited to attend his talk. His abstract follows below. --------------------- Metaverses are three-dimensional virtual worlds where anyone can add and script new objects. Metaverses today, such as Second Life, are dull, lifeless, and stagnant because users can see and interact with only a tiny region around them, rather than a large and immersive world. Current metaverses impose this distance restriction on visibility and interaction in order to scale to large worlds, as the restriction avoids appreciable shared state in underlying distributed systems. We present a brief summary of the design and implementation of the Sirikata metaverse server. The Sirikata server scales to support large, complex worlds, even as it allows users to see and interact with the entire world. It achieves both goals simultaneously by leveraging properties of the real world and 3D environments in its core systems, such as a novel distributed data structure for virtual object queries based on visible size. A virtual-world environment becomes a truly engaging platform when users have the ability to insert 3D content into the world. However, arbitrary 3D content is often not optimized for real-time rendering, limiting the ability of clients to display large scenes consisting of hundreds or thousands of objects. We present the design and implementation of an automatic, unsupervised conversion process that transforms 3D content into a format suitable for real-time rendering while minimizing loss of quality. The resulting progressive format includes a base mesh, allowing clients to quickly display the model, and a progressive portion for streaming additional detail as desired. Sirikata’s public, open-source content repository is currently using this method and has processed over 700 3D models. 3D meshes are large--often several megabytes in size. When a client enters a scene containing many objects, it can take a long time to download meshes, resulting in poor visual fidelity. A progressive mesh format allows a client to download a low-resolution version of a mesh at a much lower cost in bandwidth, but deciding how to order downloads has a huge impact on performance. Should a client download a higher texture resolution for one model, or stream additional vertices for another? Worse, underpowered clients might not be able to display a high resolution mesh, resulting in wasted time downloading unneeded content. We present the design and implementation of a framework for evaluating scheduling algorithms for progressive meshes and we perform this evaluation on several different algorithms. The result is a mesh scheduling algorithm that optimizes for visual fidelity given a fixed bandwidth constraint.

1 0

W Clarkson FPO
by Melissa M. Lawson 03 Apr '12

03 Apr '12

Will Clarkson will present his FPO on Monday April 9 at 8:30AM in the 3rd Floor Conference Room in Sherrerd Hall. Note time and location! The members of his committee are: Ed Felten, advisor; Andrew Appel and Adam Finkelstein, readers; Brian Kernighan and Rebecca Fiebrink, nonreaders. A copy of his thesis, "Breaking Assumptions: Distinguishing Between Seemingly identical Items Using Cheap Sensors", is on display in Room 310. Everyone is invited to attend his talk.

1 0