Performance of a simple optimiser using different fragment lengths L and move sizes M as a function of noise for (a) F = 5 and (b) F = 25. We mainly consider settings where L = M (as used in standard Rosetta), but the graph for L = 18, M = 3 is used to illustrate an additional effect of search space size. Performance is assessed using the mean number of iterations required to identify a solution with MSE (≤ 9, over 100 runs). The results demonstrate clearly that optimal move size decreases, as noise levels increase. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]