an improving successor state is found, the remaining of the actions are not processed, thus avoiding to compute all the applicable to the current state actions. Note however that it is not guaranteed that these actions can always be applied to the current state. In case where no improving state can be found, the remaining of the applicable to the current state actions are taken into account.

Figure 13 presents comparative performance results in *logistics* and *elevator* problems, using both search strategies. In the *logistics* problems, the *most promising facts* selection method of enhancing the goals has been used. As it results from the experimental data, in the *logistics* problems and with the use of the hill-climbing strategy, there is a significant reduction in the solution time of about 52%. The cost is an increment of about 3% in the length of the plans. In the elevator problems, there is also a reduction in the solution time of about 29%, whereas the produced plans are identical.

![0_image_0.png](0_image_0.png)

We tested the efficiency of the fast action selection mechanism, by also running GRT with the hill-climbing strategy but without this mechanism in the same *logistics* and *elevator* problems. 

Concerning the *logistics* problems, the speedup was about 47%, while the increment in the solution length was 3% on average again. Concerning the elevator problems, the speedup was 28%, whereas the produced plans were again identical. The conclusion from these additional measurements is that the speedup is primarily due to the hill-climbing strategy and secondly due to the fast action selection mechanism. The contribution of this mechanism depends on the domain and it is more important in the *logistics* and less in the *elevator*. Its inefficiency in the *elevator* domain means that the actions that are selected by this mechanism do not usually lead to an improving state or they are not applicable, so all the applicable actions have to be computed.

Results for other domains, like *blocks-world* and *freecell*, are not presented, since in these domains hill-climbing usually fails to find a plan and GRT restarts on a best-first basis. However, in 