

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

only one problem while being slightly better in 6 problems. In this domain, it seems that there is big improvement from zero to one look-ahead, while infinite-lookahead is a slight improvement over one-lookahead. (The plots for the Rovers domain are not shown in the figure as all the different look-ahead options seem to lead to near identical results in that domain.) Finally, since the heuristic is based completely on cost (α =1), we do not, in theory, expect to see any conclusive patterns in the makespan values of the solutions produced for the different lookahead options.

## 8.1.2 Utility Of The Resource Adjustment Technique

In our previous work (Do & Kambhampati, 2001), we show that the resource adjustment technique can lead to significant quality and search speed improvements in problems such as the metric temporal logistics domain in which there are several types of resource consumption objects like trucks and airplanes.

In the competition, there are two domains in which we can test the utility of the resource adjustment technique discussed in Section 5.2. The ZenoTravel domain and the Rovers domain have actions consuming resources and other (refueling) actions to renew them. Of these, the resource adjustment technique gives mixed results in the ZenoTravel domain and has no effect in the Rovers domain. Therefore, we only show the comparison for the ZenoTravel domain in Figure 15. In the ZenoTravel domain, Sapa with the resource adjustment runs slightly faster in 10 of 14 problems, returns shorter solutions in 5 problems and longer solutions in 3 problems. The solution makespan with the resource adjustment technique is also generally better than without the adjustment technique. In conclusion, the resource adjustment technique indeed helps Sapa in this domain.

In contrast, in the Rovers domain, this technique is of virtually no help. Actually, in the Rovers domain, the number of search nodes with and without the resource adjustment is the same for all solved problems. One reason maybe that in the Rovers domain, there are additional constraints on the *recharge* action so that it can only be carried out at a certain location. Therefore, even if we know that we need to add a recharge action to the current relaxed plan, we may not be able to add it because the plan does not visit the right location.