3D DISCRETE DISLOCATION DYNAMICS APPLIED TO ... - NUMODIS

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84 Parallelization of the Discrete Dislocation Dynamics method Time per step(seconds) 160 140 120 100 80 60 40 20 0 0 5 10 15 20 25 30 35 40 Number of CPUs N=77198 N=57605 N=37182 N=13185 Figure 3.18: Elapsed time per step, in seconds, as a function of the number of processors for 13185, 37182, 57605 and 77198 segments. 100. Fig.3.18 shows the average elapsed time required to complete one time step using up to 36 processors in a 2D array of processors on the IBM p690 architecture with 1.7GHz POWER4 processors 13 . Fig.3.19 shows the speedup of each number of processors and compares the actual data with the speedup model. Measured data agrees well with the model except in the 13185 segments case. The speedup decrease in the 13185 segments case for large values of P is due to the the proportion of the computation time over the communication time decreases with the number of processors. 3.4.4 Load balancing As pointed out in Sec. 3.4.2, good load balancing is crucial to achieve high performance of a parallel computation. In many cases, DDD simulations involve highly heterogeneous dislocation structures. An example is the formation of intense slip bands in fatigue simulations as shown in Fig. 3.21 (see Sec. 4.3). Fig. 3.21 shows the worst case in load balancing, due to the inherent highly heterogeneous 13 The author would like to acknowledge the support from KISTI (Korea Institute of Science and Technology Information) under "the 5th Strategic Supercomputing Applications Support Program’ with Dr. Sangmin LEE as the technical supporter. The use of the computing system of the Supercomputing Center is also greatly appreciated.
3.4 Performance improvment 85 Speedup 40 35 30 25 20 15 10 5 0 Ideal case N=37182 N=57605 N=77198 N=13185 t c =0.015t s stress 0 5 10 15 20 25 30 35 40 Number of CPUs Figure 3.19: Speedup by using P processors in 2D array for 13185, 37182, 57605 and 77198 segments (on IBM p690 architecture) Efficiency 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 Ideal case N=37182 N=57605 N=77198 N=13185 0 5 10 15 20 25 30 35 40 Number of CPUs Figure 3.20: Efficiency by using P processors in 2D array for 13185, 37182, 57605 and 77198 segments (on IBM p690 architecture)
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INSTITUT NATIONAL POLYTECHNIQUE DE
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Acknowledgements First of all, I ex
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Résumé La dynamique des dislocati
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viii CONTENTS 2.3.5 Plastic strain
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Chapter 1 Introduction 1.1 Computat
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1.2 Dislocation dynamics 3 (a) Weak
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1.3 Scope of Thesis 5 Recently the
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1.3 Scope of Thesis 7 coupling meth
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10 Description of the simulation me
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4.3 Fatigue simulations of material
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Chapter 5 Conclusions and perspecti
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namics codes into a parallel versio
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Bibliography [Abraham 97] Abraham F
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BIBLIOGRAPHY 155 [Devincre & Robert
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BIBLIOGRAPHY 157 [Khraishi et al. 0
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BIBLIOGRAPHY 159 [Risbet et al. 03]
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3D DISCRETE DISLOCATION DYNAMICS APPLIED TO ... - NUMODIS

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