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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Self-tuned parallel runtimes: a case of study for OpenMP

Durán González, Alejandro 22 October 2008 (has links)
In recent years parallel computing has become ubiquitous. Lead by the spread of commodity multicore processors, parallel programming is not anymore an obscure discipline only mastered by a few.Unfortunately, the amount of able parallel programmers has not increased at the same speed because is not easy to write parallel codes.Parallel programming is inherently different from sequential programming. Programmers must deal with a whole new set of problems: identification of parallelism, work and data distribution, load balancing, synchronization and communication.Parallel programmers have embraced several languages designed to allow the creation of parallel applications. In these languages, the programmer is not only responsible of identifying the parallelism but also of specifying low-level details of how the parallelism needs to exploited (e.g. scheduling, thread distribution ...). This is a burden than hampers the productivity of the programmers.We demonstrate that is possible for the runtime component of a parallel environment to adapt itself to the application and the execution environment and thus reducing the burden put into the programmer. For this purpose we study three different parameters that are involved in the parallel exploitation of the OpenMP parallel language: parallel loop scheduling, thread allocation in multiple levels of parallelism and task granularity control.In all the cases, we propose a self-tuned algorithm that will first perform an on-line profiling of the application and based on the information gathered it will adapt the value of the parameter to the one that maximizes the performance of the application.Our goal is not to develop methods that outperform a hand-tuned application for a specific scenario, as this is probably just as difficult as compiler code outperforming hand-tuned assembly code, but methods that get close to that performance with a minimum effort from the programmer. In other words, what we want to achieve with our self-tuned algorithms is to maximize the ratio performance over effort so the entry level to the parallelism is lower. The evaluation of our algorithms with different applications shows that we achieve that goal.
2

Feature Construction Using Evolution-COnstructed Features for General Object Recognition

Lillywhite, Kirt D. 05 March 2012 (has links) (PDF)
Object recognition is a well studied but extremely challenging field. Human detection is an especially important part of object recognition as it has played a role in machine and human interaction, biometrics, unmanned vehicles, as well as tracking and surveillance. We first present a hardware implementation of the successful Histograms of Oriented Gradients (HOG) method for human detection. The implementation significantly speeds up the method achieving 38 frames a second on VGA video while testing 11,160 sliding windows per frame. The accuracy remains comparable to the CPU implementation. Analysis of the HOG method and other popular object recognition methods led to a novel approach for object detection using a feature construction method called Evolution-COnstructed (ECO) features. Most other approaches rely on human experts to construct features for object recognition. ECO features are automatically constructed by uniquely employing a standard genetic algorithm to discover series of transforms that are highly discriminative. Using ECO features provides several advantages over other object detection algorithms including: no need for a human expert to build feature sets or tune their parameters, ability to generate specialized feature sets for different objects, and no limitations to certain types of image sources. We show in our experiments that ECO features perform better or comparable with state-of-the-art object recognition algorithms making it the first feature construction method to compete with features created by human experts at general object recognition. An analysis is given of ECO features which includes a visualization of ECO features and improvements made to the algorithm.

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