Uma extensão à OpenMP para suporte à memória transacional

Abstract

One of the most complex aspects of developing programs in environments with shared memory is the synchronization of concurrent activities accessing shared data. Transactional Memory was proposed as a mechanism that abstracts some of the complexities associated with concurrent access to shared data while promoting the development of more readable programs by offering a higher-level programming interface. Although the modern tools for multithreaded programming offer resources for efficient exploitation of the hardware, the supports for synchronization to shared data still reflect models based on the synchronization of execution flows. The aim of the work is to extend the state of the art in interfaces for multithreaded concurrent programming by introducing features for handling Transactional Memory in consolidated programming tools. The objective was achieved by the characterization of an extension to OpenMP, allowing the manipulation of data in a transactional way. Unlike other similar approaches found in the bibliography, the proposal presented stands out for performing synchronization on the data and not on the execution flows, as predicted in the Transactional Memory model itself. In the thesis, the specification of the proposed extension, its prototyping, and its qualitative and quantitative validation are presented. Qualitative validation took place by comparison, considering metrics obtained by code analysis, between the codes obtained in implementations of different applications in programs using the proposed extension with other solutions. This analysis indicated that the solution presented met the desired abstraction requirements. The prototype, built to verify the feasibility of implementing the interface, was also evaluated in terms of performance, in the quantitative analysis. The prototype was built in the form of an intermediate language, allowing to instantiate the program on different tools to support Transactional Memory in software. The performance analyzes considered a varied set of case studies, and the analysis of the results allowed to attest the feasibility of implementing the proposed interface.