Abstract. This paper describes an implementation of the Unordered Parallel Reverse Cuthill-McKee algorithm which is compared with its well-known serial version. The OpenMP framework is used for supporting the parallelism and a strategy for reducing lazy threads is evaluated. Large sparse matrices are used to test sequential and parallel approaches. The computational cost reduction and the quality of matrices bandwidth minimization are validated by CPU time and speedup.
Abstract-This work presents a new parallel non-speculative implementation of the Unordered Reverse Cuthill-McKee algorithm. Reordering quality (bandwidth reduction) and reordering performance (CPU time) are evaluated in comparison with a serial implementation of the algorithm made available by the state-of-the-art mathematical software library HSL. The bandwidth reductions reached by our parallel RCM were more than 90% for several large matrices out of the ones tested, and the time reordering improvement was up to 57.82%. Speedups higher than 3.0X were achieved with the parallel RCM. The underlying parallelism was supported by the OpenMP framework and three strategies for reducing idle threads were incorporated into the algorithm.
This work presents a parallel implementation of a graph-generating algorithm designed to be straightforwardly adapted to traverse large datasets. This new approach has been validated in a correlated scenario known as the word ladder problem. The new parallel algorithm induces the same topological structure proposed by its serial version and also builds the shortest path between any pair of words to be connected by a ladder of words. The implemented parallelism paradigm is the Multiple Instruction Stream - Multiple Data Stream (MIMD) and the test suite embraces 23-word ladder instances whose intermediate words were extracted from a dictionary of 183,719 words (dataset). The word morph quality (the shortest path between two input words) and the word morph performance (CPU time) were evaluated against a serial implementation of the original algorithm. The proposed parallel algorithm generated the optimal solution for each pair of words tested, that is, the minimum word ladder connecting an initial word to a final word was found. Thus, there was no negative impact on the quality of the solutions comparing them with those obtained through the serial ANG algorithm. However, there was an outstanding improvement considering the CPU time required to build the word ladder solutions. In fact, the time improvement was up to 99.85%, and speedups greater than 2.0X were achieved with the parallel algorithm.
Controladores de redes OpenFlow vêm sendo implementados por meio de diversas iniciativas em paralelo e em distintas linguagens de programação. Essa diversidade gera um potencial impacto sobre a usabilidade dos controladores enquanto plataformas de desenvolvimento. Este trabalho apresenta uma análise comparativa da usabilidade de diferentes controladores implementados na linguagem Java. A avaliação foi feita sob a perspectiva do desenvolvimento de uma aplicação para rede OpenFlow. Um conjunto de critérios de usabilidade foi definido a fim de estabelecer os parâmetros da análise efetuada.
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