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Multitasking a Navier-Stokes algorithm on the CRAY-2

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Abstract

This paper presents the results of multitasking a Navier-Stokes algorithm on the CRAY-2. The algorithm is a compact difference scheme for the solution of the incompressible, two-dimensional, time-dependent Navier-Stokes equations. Two implementations of multitasking on the CRAY-2 are considered: macrotasking (parallelism at the subroutine level) and microtasking (parallelism at the do-loop level). These two techniques are briefly described. The implementation of the algorithm is discussed in relation to these techniques, and the results for three problem sizes are presented. The timing results for both techniques are, in general, comparable with differences ranging between 2% and 14%, depending on the problem size. The best achieved speedup in a dedicated environment is 3.62 for macrotasking and 3.32 for microtasking. The task granularity for both techniques is computed, and the synchronization costs are estimated. For macrotasks of granularity of up to 0.5 msec, microtasking outperformed macrotasking, while the latter outperformed the former for granularity of over one msec.

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Authors and Affiliations

  1. Sterling Software, 94303, Palo Alto, CA, USA

    R. A. Fatoohi

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  1. R. A. Fatoohi
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This research was supported by NASA Contract No. NAS2-11555 while the author was an employee of Sterling Software under contract to the Numerical Aerodynamic Simulation Systems Divison at NASA Ames Research Center, Moffett Field, CA 94035.

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Fatoohi, R.A. Multitasking a Navier-Stokes algorithm on the CRAY-2. J Supercomput 3, 109–124 (1989). https://doi.org/10.1007/BF00129845

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