1,470 research outputs found
Analysis of Crowdsourced Sampling Strategies for HodgeRank with Sparse Random Graphs
Crowdsourcing platforms are now extensively used for conducting subjective
pairwise comparison studies. In this setting, a pairwise comparison dataset is
typically gathered via random sampling, either \emph{with} or \emph{without}
replacement. In this paper, we use tools from random graph theory to analyze
these two random sampling methods for the HodgeRank estimator. Using the
Fiedler value of the graph as a measurement for estimator stability
(informativeness), we provide a new estimate of the Fiedler value for these two
random graph models. In the asymptotic limit as the number of vertices tends to
infinity, we prove the validity of the estimate. Based on our findings, for a
small number of items to be compared, we recommend a two-stage sampling
strategy where a greedy sampling method is used initially and random sampling
\emph{without} replacement is used in the second stage. When a large number of
items is to be compared, we recommend random sampling with replacement as this
is computationally inexpensive and trivially parallelizable. Experiments on
synthetic and real-world datasets support our analysis
Real-time deformation and fracture in a game environment
This paper describes a simulation system that has been developed to model the deformation and fracture of solid objects in a real-time gaming context. Based around a corotational tetrahedral finite element method, this system has been constructed from components published in the graphics and computational physics literatures. The goal of this paper is to describe how these components can be combined to produce an engine that is robust to unpredictable user interactions, fast enough to model reasonable scenarios at real-time speeds, suitable for use in the design of a game level, and with appropriate controls allowing content creators to match artistic direction. Details concerning parallel implementation, solver design, rendering method, and other aspects of the simulation are elucidated with the intent of providing a guide to others wishing to implement similar systems. Examples from in-game scenes captured on the Xbox 360, PS3, and PC platforms are included. © 2009 ACM
Rapid Parallelization by Collaboration
The widespread adoption of Chip Multiprocessors has renewed the emphasis on the use of parallelism to improve performance. The present and growing diversity in hardware architectures and software environments, however, continues to pose difficulties in the effective use of parallelism thus delaying a quick and smooth transition to the concurrency era. In this document, we describe the research being conducted at the Computer Science Department at Columbia University on a system called COMPASS that aims to simplify this transition by providing advice to programmers considering parallelizing their code. The advice proffered to the programmer is based on the wisdom collected from programmers who have already parallelized some code. The utility of COMPASS rests, not only on its ability to collect the wisdom unintrusively but also on its ability to automatically seek, find and synthesize this wisdom into advice that is tailored to the code the user is considering parallelizing and to the environment in which the optimized program will execute in. COMPASS provides a platform and an extensible framework for sharing human expertise about code parallelization -- widely and on diverse hardware and software. By leveraging the "Wisdom of Crowds" model which has been conjunctured to scale exponentially and which has successfully worked for Wikis, COMPASS aims to enable rapid parallelization of code and thus continue to extend the benefits for Moore's law scaling to science and society
Ten Quick Tips for Using a Raspberry Pi
Much of biology (and, indeed, all of science) is becoming increasingly
computational. We tend to think of this in regards to algorithmic approaches
and software tools, as well as increased computing power. There has also been a
shift towards slicker, packaged solutions--which mirrors everyday life, from
smart phones to smart homes. As a result, it's all too easy to be detached from
the fundamental elements that power these changes, and to see solutions as
"black boxes". The major goal of this piece is to use the example of the
Raspberry Pi--a small, general-purpose computer--as the central component in a
highly developed ecosystem that brings together elements like external
hardware, sensors and controllers, state-of-the-art programming practices, and
basic electronics and physics, all in an approachable and useful way. External
devices and inputs are easily connected to the Pi, and it can, in turn, control
attached devices very simply. So whether you want to use it to manage
laboratory equipment, sample the environment, teach bioinformatics, control
your home security or make a model lunar lander, it's all built from the same
basic principles. To quote Richard Feynman, "What I cannot create, I do not
understand".Comment: 12 pages, 2 figure
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3D TV: A Scalable System for Real-Time Acquisition, Transmission, and Autostereoscopic Display of Dynamic Scenes
Three-dimensional TV is expected to be the next revolution in the history of television. We implemented a 3D TV prototype system with real-time acquisition, transmission, and 3D display of dynamic scenes. We developed a distributed, scalable architecture to manage the high computation and bandwidth demands. Our system consists of an array of cameras, clusters of network-connected PCs, and a multi-projector 3D display. Multiple video streams are individually encoded and sent over a broadband network to the display. The 3D display shows high-resolution (1024 × 768) stereoscopic color images for multiple viewpoints without special glasses. We implemented systems with rear-projection and front-projection lenticular screens. In this paper, we provide a detailed overview of our 3D TV system, including an examination of design choices and tradeoffs. We present the calibration and image alignment procedures that are necessary to achieve good image quality. We present qualitative results and some early user feedback. We believe this is the first real-time end-to-end 3D TV system with enough views and resolution to provide a truly immersive 3D experience.Engineering and Applied Science
Parallel Tempering Simulation of the three-dimensional Edwards-Anderson Model with Compact Asynchronous Multispin Coding on GPU
Monte Carlo simulations of the Ising model play an important role in the
field of computational statistical physics, and they have revealed many
properties of the model over the past few decades. However, the effect of
frustration due to random disorder, in particular the possible spin glass
phase, remains a crucial but poorly understood problem. One of the obstacles in
the Monte Carlo simulation of random frustrated systems is their long
relaxation time making an efficient parallel implementation on state-of-the-art
computation platforms highly desirable. The Graphics Processing Unit (GPU) is
such a platform that provides an opportunity to significantly enhance the
computational performance and thus gain new insight into this problem. In this
paper, we present optimization and tuning approaches for the CUDA
implementation of the spin glass simulation on GPUs. We discuss the integration
of various design alternatives, such as GPU kernel construction with minimal
communication, memory tiling, and look-up tables. We present a binary data
format, Compact Asynchronous Multispin Coding (CAMSC), which provides an
additional speedup compared with the traditionally used Asynchronous
Multispin Coding (AMSC). Our overall design sustains a performance of 33.5
picoseconds per spin flip attempt for simulating the three-dimensional
Edwards-Anderson model with parallel tempering, which significantly improves
the performance over existing GPU implementations.Comment: 15 pages, 18 figure
Control System in Open-Source FPGA for a Self-Balancing Robot
Computing in technological applications is typically performed with software running on
general-purpose microprocessors, such as the Computer Processing Unit (CPU), or specific ones,
like the Graphical Processing Unit (GPU). Application-Specific Integrated Circuits (ASICs) are an
interesting option when speed and reliability are required, but development costs are usually high.
Field-Programmable Gate Arrays (FPGA) combine the flexibility of software with the high-speed
operation of hardware, and can keep costs low. The dominant FPGA infrastructure is proprietary, but
open tools have greatly improved and are a growing trend, from which robotics can benefit. This
paper presents a robotics application that was fully developed using open FPGA tools. An inverted
pendulum robot was designed, built, and programmed using open FPGA tools, such as IceStudio and
the IceZum Alhambra board, which integrates the iCE40HX4K-TQ144 from Lattice. The perception
from an inertial sensor is used in a PD control algorithm that commands two DC motors. All the
modules were synthesized in an FPGA as a proof of concept. Its experimental validation shows good
behavior and performance.This work was partially funded by the Community of Madrid through the RoboCity2030-III project
(S2013/MIT-2748) and by the Spanish Ministry of Economy and Competitiveness through the RETOGAR project
(TIN2016-76515-R)
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