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A Study of Parallel Efficiency of Modified Direct Algorithm Applied to Thermohydrodynamic Lubrication

Published online by Cambridge University Press:  05 May 2011

N. Wang ,
C.-M. Tsai  and
K.-C. Cha
N. Wang*
Affiliation:
Department of Mechanical Engineering, Chang Gung University, Tao-Yuan, Taiwan 33302, R.O.C.
C.-M. Tsai*
Affiliation:
Department of Mechanical Engineering, Chang Gung University, Tao-Yuan, Taiwan 33302, R.O.C.
K.-C. Cha*
Affiliation:
Department of Mechanical Engineering, Chang Gung University, Tao-Yuan, Taiwan 33302, R.O.C.
*
*Professor, corresponding author
**Ph.D. student
***Assistant Professor
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Abstract

This study examines the parallel computing as a means to minimize the execution time in the optimization applied to thermohydrodynamic (THD) lubrication. The objective of the optimization is to maximize the load capacity of a slider bearing with two design variables. A global optimization method, DIviding RECTangle (DIRECT) algorithm, is used. The first approach was to apply the parallel computing within the THD model in a shared-memory processing (SMP) environment to examine the parallel efficiency of fine-grain computation. Next, a distributed parallel computing in the search level was conducted by use of the standard DIRECT algorithm. Then, the algorithm is modified to provide a version suitable for effective parallel computing. In the latter coarse-grain computation the speedups obtained by the DIRECT algorithms are compared with some previous studies using other parallel optimization methods. In the fine-grain computation of the SMP machine, the communication and overhead time costs prohibit high speedup in the cases of four or more simultaneous threads. It is found that the standard DIRECT algorithm is an efficient sequential but less parallel-computing-friendly method. When the modified algorithm is used in the slider bearing optimization, a parallel efficiency of 96.3% is obtained in the 16-computing-node cluster. This study presents the modified DIRECT algorithm, an efficient parallel search method, for general engineering optimization problems.

Keywords

OptimizationParallel computingThermohydrodynamic lubricationDIRECT algorithm.
Type
Articles
Information
Journal of Mechanics , Volume 25 , Issue 2 , June 2009 , pp. 143 - 150
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2009

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