287 research outputs found
Definition of a Method for the Formulation of Problems to be Solved with High Performance Computing
Computational power made available by current technology has been continuously increasing, however today’s problems are larger and more complex and demand even more computational power. Interest in computational problems has also been increasing and is an important research area in computer science. These complex problems are solved with computational models that use an underlying mathematical model and are solved using computer resources, simulation, and are run with High Performance Computing. For such computations, parallel computing has been employed to achieve high performance. This thesis identifies families of problems that can best be solved using modelling and implementation techniques of parallel computing such as message passing and shared memory. Few case studies are considered to show when the shared memory model is suitable and when the message passing model would be suitable. The models of parallel computing are implemented and evaluated using some algorithms and simulations. This thesis mainly focuses on showing the more suitable model of computing for the various scenarios in attaining High Performance Computing
GPU Computing to Improve Game Engine Performance
Although the graphics processing unit (GPU) was originally designed to accelerate the image creation for output to display, today's general purpose GPU (GPGPU) computing offers unprecedented performance by offloading computing-intensive portions of the application to the GPGPU, while running the remainder of the code on the central processing unit (CPU). The highly parallel structure of a many core GPGPU can process large blocks of data faster using multithreaded concurrent processing. A game engine has many "components" and multithreading can be used to implement their parallelism. However, effective implementation of multithreading in a multicore processor has challenges, such as data and task parallelism. In this paper, we investigate the impact of using a GPGPU with a CPU to design high-performance game engines. First, we implement a separable convolution filter (heavily used in image processing) with the GPGPU. Then, we implement a multiobject interactive game console in an eight-core workstation using a multithreaded asynchronous model (MAM), a multithreaded synchronous model (MSM), and an MSM with data parallelism (MSMDP). According to the experimental results, speedup of about 61x and 5x is achieved due to GPGPU and MSMDP implementation, respectively. Therefore, GPGPU-assisted parallel computing has the potential to improve multithreaded game engine performance
Improving GPU SIMD Control Flow Efficiency via Hybrid Warp Size Mechanism
High single instruction multiple data (SIMD) efficiency and low power consumption have made graphic processing units (GPUs) an ideal platform for many complex computational applications. Thousands of threads can be created by programmers and grouped into fixed-size SIMD batches, known as warps. High throughput is then achieved by concurrently executing such warps with minimal control overhead. However, if a branch instruction occurs, which assigns different paths to different threads, this warp will be broken into multiple warps that have to be executed serially, consequently reducing the efficiency advantage of SIMD.
In this thesis, the contemporary fixed-size warp design is abandoned and a hybrid warp size (HWS) mechanism is proposed. Mixed-size warps are generated according to HWS and are scheduled and issued flexibly. Once a branch divergence occurs, split warps are squeezed according to the proposed algorithm, and warp sizes are downscaled wherever applicable. Based on updated warp sizes, warp schedulers calculate the number of cycles the current warp needs and issue the next warp accordingly. As a result, hybrid warps are pushed into pipelines as soon as possible and more pipeline stages are overlapped. The simulation results show that this mechanism yields an average speedup of 1.20 over the baseline architecture for a wide variety of general purpose GPU applications.
This work also integrates HWS with dynamic warp formation (DWF), which is a well-known branch handling mechanism aimed at improving SIMD utilization by forming new warps out of split warps in real time. The warp forming policy is modified to better tolerate warp conflicts. Also, squeeze operations are added before a warp merges with other warps. The simulation shows that the combination of DWF and HWS generates an average speedup of 1.27 over the DWF-only platform for the same set of GPU benchmarks
Adaptive Parallel Iterative Deepening Search
Many of the artificial intelligence techniques developed to date rely on
heuristic search through large spaces. Unfortunately, the size of these spaces
and the corresponding computational effort reduce the applicability of
otherwise novel and effective algorithms. A number of parallel and distributed
approaches to search have considerably improved the performance of the search
process. Our goal is to develop an architecture that automatically selects
parallel search strategies for optimal performance on a variety of search
problems. In this paper we describe one such architecture realized in the
Eureka system, which combines the benefits of many different approaches to
parallel heuristic search. Through empirical and theoretical analyses we
observe that features of the problem space directly affect the choice of
optimal parallel search strategy. We then employ machine learning techniques to
select the optimal parallel search strategy for a given problem space. When a
new search task is input to the system, Eureka uses features describing the
search space and the chosen architecture to automatically select the
appropriate search strategy. Eureka has been tested on a MIMD parallel
processor, a distributed network of workstations, and a single workstation
using multithreading. Results generated from fifteen puzzle problems, robot arm
motion problems, artificial search spaces, and planning problems indicate that
Eureka outperforms any of the tested strategies used exclusively for all
problem instances and is able to greatly reduce the search time for these
applications
A RECONFIGURABLE AND EXTENSIBLE EXPLORATION PLATFORM FOR FUTURE HETEROGENEOUS SYSTEMS
Accelerator-based -or heterogeneous- computing has become increasingly
important in a variety of scenarios, ranging from High-Performance Computing (HPC) to embedded systems. While most solutions use sometimes
custom-made components, most of today’s systems rely on commodity highend CPUs and/or GPU devices, which deliver adequate performance while
ensuring programmability, productivity, and application portability. Unfortunately, pure general-purpose hardware is affected by inherently limited
power-efficiency, that is, low GFLOPS-per-Watt, now considered as a primary metric. The many-core model and architectural customization can
play here a key role, as they enable unprecedented levels of power-efficiency
compared to CPUs/GPUs. However, such paradigms are still immature and
deeper exploration is indispensable.
This dissertation investigates customizability and proposes novel solutions
for heterogeneous architectures, focusing on mechanisms related to coherence and network-on-chip (NoC). First, the work presents a non-coherent
scratchpad memory with a configurable bank remapping system to reduce
bank conflicts. The experimental results show the benefits of both using a
customizable hardware bank remapping function and non-coherent memories for some types of algorithms. Next, we demonstrate how a distributed
synchronization master better suits many-cores than standard centralized
solutions. This solution, inspired by the directory-based coherence mechanism, supports concurrent synchronizations without relying on memory
transactions. The results collected for different NoC sizes provided indications about the area overheads incurred by our solution and demonstrated
the benefits of using a dedicated hardware synchronization support. Finally, this dissertation proposes an advanced coherence subsystem, based
on the sparse directory approach, with a selective coherence maintenance
system which allows coherence to be deactivated for blocks that do not require it. Experimental results show that the use of a hybrid coherent and
non-coherent architectural mechanism along with an extended coherence
protocol can enhance performance.
The above results were all collected by means of a modular and customizable heterogeneous many-core system developed to support the exploration
of power-efficient high-performance computing architectures. The system is
based on a NoC and a customizable GPU-like accelerator core, as well as
a reconfigurable coherence subsystem, ensuring application-specific configuration capabilities. All the explored solutions were evaluated on this real heterogeneous system, which comes along with the above methodological
results as part of the contribution in this dissertation. In fact, as a key
benefit, the experimental platform enables users to integrate novel hardware/software solutions on a full-system scale, whereas existing platforms
do not always support a comprehensive heterogeneous architecture exploration
An automated OpenCL FPGA compilation framework targeting a configurable, VLIW chip multiprocessor
Modern system-on-chips augment their baseline CPU with coprocessors and accelerators to increase overall computational capacity and power efficiency, and thus have evolved into heterogeneous systems. Several languages have been developed to enable this paradigm shift, including CUDA and OpenCL. This thesis discusses a unified compilation environment to enable heterogeneous system design through the use of OpenCL and a customised VLIW chip multiprocessor (CMP) architecture, known as the LE1. An LLVM compilation framework was researched and a prototype developed to enable the execution of OpenCL applications on the LE1 CPU. The framework fully automates the compilation flow and supports work-item coalescing to better utilise the CPU cores and alleviate the effects of thread divergence. This thesis discusses in detail both the software stack and target hardware architecture and evaluates the scalability of the proposed framework on a highly precise cycle-accurate simulator. This is achieved through the execution of 12 benchmarks across 240 different machine configurations, as well as further results utilising an incomplete development branch of the compiler. It is shown that the problems generally scale well with the LE1 architecture, up to eight cores, when the memory system becomes a serious bottleneck. Results demonstrate superlinear performance on certain benchmarks (x9 for the bitonic sort benchmark with 8 dual-issue cores) with further improvements from compiler optimisations (x14 for bitonic with the same configuration
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