Enhancing productivity and performance portability of opencl applications on heterogeneous systems using runtime optimizations

Initially driven by a strong need for increased computational performance in science and engineering, heterogeneous systems have become ubiquitous and they are getting increasingly complex. The single processor era has been replaced with multi-core processors, which have quickly been surrounded by satellite devices aiming to increase the throughput of the entire system. These auxiliary devices, such as Graphics Processing Units, Field Programmable Gate Arrays or other specialized processors have very different architectures. This puts an enormous strain on programming models and software developers to take full advantage of the computing power at hand. Because of this diversity and the unachievable flexibility and portability necessary to optimize for each target individually, heterogeneous systems remain typically vastly under-utilized. In this thesis, we explore two distinct ways to tackle this problem. Providing automated, non intrusive methods in the form of compiler tools and implementing efficient abstractions to automatically tune parameters for a restricted domain are two complementary approaches investigated to better utilize compute resources in heterogeneous systems. First, we explore a fully automated compiler based approach, where a runtime system analyzes the computation flow of an OpenCL application and optimizes it across multiple compute kernels. This method can be deployed on any existing application transparently and replaces significant software engineering effort spent to tune application for a particular system. We show that this technique achieves speedups of up to 3x over unoptimized code and an average of 1.4x over manually optimized code for highly dynamic applications. Second, a library based approach is designed to provide a high level abstraction for complex problems in a specific domain, stencil computation. Using domain specific techniques, the underlying framework optimizes the code aggressively. We show that even in a restricted domain, automatic tuning mechanisms and robust architectural abstraction are necessary to improve performance. Using the abstraction layer, we demonstrate strong scaling of various applications to multiple GPUs with a speedup of up to 1.9x on two GPUs and 3.6x on four

Efficient execution of Java programs on GPU

Dissertação de mestrado em Informatics EngineeringWith the overwhelming increase of demand of computational power made by fields as Big Data, Deep Machine learning and Image processing the Graphics Processing Units (GPUs) has been seen as a valuable tool to compute the main workload involved. Nonetheless, these solutions have limited support for object-oriented languages that often require manual memory handling which is an obstacle to bringing together the large community of object oriented programmers and the high-performance computing field. In this master thesis, different memory optimizations and their impacts were studied in a GPU Java context using Aparapi. These include solutions for different identifiable bottlenecks of commonly used kernels exploiting its full capabilities by studying the GPU hardware and current techniques available. These results were set against common used C/OpenCL benchmarks and respective optimizations proving, that high-level languages can be a solution to high-performance software demand.Com o aumento de poder computacional requisitado por campos como Big Data, Deep Machine Learning e Processamento de Imagens, as unidades de processamento gráfico (GPUs) tem sido vistas como uma ferramenta valiosa para executar a principal carga de trabalho envolvida. No entanto, esta solução tem suporte limitado para linguagens orientadas a objetos. Frequentemente estas requerem manipulação manual de memória, o que é um obstáculo para reunir a grande comunidade de programadores orientados a objetos e o campo da computação de alto desempenho. Nesta dissertação de mestrado, diferentes otimizações de memória e os seus impactos foram estudados utilizando Aparapi. As otimizações estudadas pretendem solucionar bottle-necks identificáveis em kernels frequentemente utilizados. Os resultados obtidos foram comparados com benchmarks C / OpenCL populares e as suas respectivas otimizações, provando que as linguagens de alto nível podem ser uma solução para programas que requerem computação de alto desempenho

Design and implementation of a generalised computer aided learning system

This thesis surveys the development of computer aided learning and outlines the tools that are used for creating computer aided learning systems. A project to create and port over a computer aided learning system from a VAX 11/750 to a PDF model 11/44 based on the UNIX operating system is described. The computer aided learning system makes extensive use of existing software tools available on UNIX and is hence named CALUNIX for Computer Aided Learning on UNIX

BeEngine: 2D Game Engine

This document contains the description of the development of a C++ game engine named BeEngine, as the final university project. The engine is focused on 2D game development and aims to provide all the necessary components and tools to create and deploy a video game from start to finish. The result is astandalone program that can be execute dinany Windows machine, tha thas the ability to load and manage resources (such as images, scripts, audio, etc.), and allows the user to implement the logic and test the results before generating the final game. This project goes through some of the techniques and the logic behind the modules and tools of this engine, and the process of implementation followed to accomplish the final results

A framework for efficient execution of data parallel irregular applications on heterogeneous systems

Exploiting the computing power of the diversity of resources available on heterogeneous systems is mandatory but a very challenging task. The diversity of architectures, execution models and programming tools, together with disjoint address spaces and di erent computing capabilities, raise a number of challenges that severely impact on application performance and programming productivity. This problem is further compounded in the presence of data parallel irregular applications. This paper presents a framework that addresses development and execution of data parallel irregular applications in heterogeneous systems. A uni ed task-based programming and execution model is proposed, together with inter and intra-device scheduling, which, coupled with a data management system, aim to achieve performance scalability across multiple devices, while maintaining high programming productivity. Intradevice scheduling on wide SIMD/SIMT architectures resorts to consumer-producer kernels, which, by allowing dynamic generation and rescheduling of new work units, enable balancing irregular workloads and increase resource utilization. Results show that regular and irregular applications scale well with the number of devices, while requiring minimal programming e ort. Consumer-producer kernels are able to sustain signi cant performance gains as long as the workload per basic work unit is enough to compensate overheads associated with intra-device scheduling. This not being the case, consumer kernels can still be used for the irregular application. Comparisons with an alternative framework, StarPU, which targets regular workloads, consistently demonstrate signi cant speedups. This is, to the best of our knowledge, the rst published integrated approach that successfully handles irregular workloads over heterogeneous systems.This work is funded by National Funds through the FCT - Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) and by ERDF - European Regional Development Fund through the COMPETE Programme (operational programme for competitiveness) within projects PEst-OE/EEI/UI0752/2014 and FCOMP-01-0124-FEDER-010067. Also by the School of Engineering, Universidade do Minho within project P2SHOCS - Performance Portability on Scalable Heterogeneous Computing Systems