Geoscience Reference
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To illustrate this further, Fig. 5.15 is presented, which shows the graph of evaluated function
values (minima and maxima) for different numbers of function evaluations. This example is for
forecasts at 84 hours with 3 subperiods and varying temporal patterns over subbasins using the
nGA. The figure clearly shows that the improvement in the function value is extremely
slow after a certain number of function evaluations. Specifically, in the evaluation of
the minimum function value (Fig. 5.15(a)) the gain in the function value is very slow
after 1000 function evaluations. Similarly, in the evaluation of the maximum function
value (Fig. 5.15(b)) the gain is very slow after 1200 function evaluations. In practical ap-
plications, it is normally not affordable to go for function evaluations as high as ten thousand
as shown in Fig. 5.15. Moreover, the difference between the same temporal pattern for all
subbasins and the temporal pattern varying over all subbasins (Fig. 5.14) is not very significant.
Therefore, for the results presented in Fig. 5.14, the function evaluations are limited to 2000.
Figure 5.15. Performance of the algorithm for the determination of (a) minima,
and (b) maxima, for the forecast at 84 h with 3 subperiods and varying
temporal patterns over subbasins using the nGA.
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