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Simulations, Data Analysis and Algorithms

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Figure 4 | Computational Astrophysics and Cosmology

Figure 4

From: On the reliability of N-body simulations

Figure 4

Scaling of Brutus . In the top left panel we show the scaling of the wall-clock time that Brutus needs as a function of number of stars N. The dotted curve is a fit to the data given by \(t_{\mathrm{CPU}} \propto N^{2.6}\). In the top right panel we show the speed-up when the number of cores, p, is increased. The bottom, solid curve represents \(N=32\) and each curve above has an N a factor two higher than the previous curve. The dotted curve represents ideal scaling. In the bottom left panel we plot the slowdown factor as a function of the Bulirsch-Stoer tolerance ϵ, for a fixed word-length of 1,024 bits. In the bottom right panel we plot the slowdown factor as a function of word-length \(L_{\mathrm{w}}\), for a fixed tolerance of 10−10. The slowdown of the simulations is mainly caused by the very small Bulirsch-Stoer tolerances required.

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