## 5 Experiment
### Experimental Results
#### 5.3.3 Robustness
However, it is interesting that the hotspot method results are more consistent than the results of the other methods. Its results are 40 to 55% in all trials, while the ACO and blind results are 20 to 60%. The ACO and blind methods produce low expiry rates in half of the trials while showing higher expiry rates in other trials. This will be further clarified in the box plot visualization. Figure 10: Average robustness of the different methods in terms of the (**a**) foraging and (**b**) expiry rates. Based on the expiry rate distribution shown in the box plot (Figure 10(f)), it can be confirmed that the centralized method is not robust to changes in the map size. Other than in the 16 \(\times\) 16 map, the distribution of the centralized method is the highest and most dispersed, indicating that it has a significantly worse expiry rate than the other methods. In the 16 \(\times\) 16 map, the centralized method results extend from 0% to 70% and are highly dispersed. This shows that even though the average expiry rate (Figure 10b) of the centralized method is the lowest in the 16 \(\times\) 16 map, from the distribution shown in Figure 10(f), this result is not guaranteed, and the expiry rate is highly inconsistent from one trial to another. In regard to the ACO, hotspot, and blind distributions (Figure 10(f)), the behavior differs from one map to another. However, the hotspot method behaves consistently in all cases, preserving a similar rank in all map sizes in comparison to the other methods. In the 40 \(\times\) 40 map, the ACO method produces the worst expiry rate distribution in comparison to the hotspot and blind methods, and it is highly dispersed and has the maximum values. Figure 11: Robustness results for 40 trials with different setups. The results are ordered from smallest to largest for better representation (**a–f**). The hotspot and blind methods, on the other hand, produce similar expiry rates in this map size. When increasing the size to 8 \(\times\) 8, the blind method has the worst expiry rate distribution, with the hotspot method still ranking in the middle, while the ACO method has the best distribution. In the 16 \(\times\) 16 map, however, the blind method produces the best distribution, while the ACO and hotspot methods have similar distributions. In the 20 \(\times\) 20 map, the blind method has the lowest minimum value but the most dispersed result, indicating that its robustness is not consistent. The ACO method is second in regard to the minimum value, but it is negatively skewed, and its results are more dispersed than those of the hotspot method. With the hotspot method, although its average expiry rate (Figure 10b) is slightly higher than those of the ACO and blind methods in the 20 \(\times\) 20 map, the distribution shows that its maximum value is lower than that of the other methods and that its results are more compressed than the other methods while also being positively skewed. This indicates that the hotspot method performance in this map is more consistent, i.e., robust, and produces results on the lower end of the scale in comparison to the other methods. In a very large map (40 \(\times\) 40), the ACO, hotspot, and blind methods have the same maximum and mean expiry rates but different minimums and dispersions. The results for the minimum expiry rate and dispersion of the hotspot method fall between the results of the ACO and blind methods. On the other hand, the blind method has the lowest expiry rate value, while ACO has the most compressed results. Therefore, from all the results of the box plot distribution (Figure 11f), it can be concluded that the hotspot method performs consistently, with an intermediate robustness in all map sizes, unlike the other methods, which offer the best results in some maps but the worst results in others.