## 5 Experiment
### Experimental Results
#### 5.3.1 Flexibility  
To analyze the flexibility of ED_Foraging with different setups, the average performance over 40 trials was collected for both the foraging and expiry rates (Figure 6). From Figure 6, it is clear that the DTA methods that use multiple collection zones, i.e., hotspot, ACO, and blind, have almost the same foraging rates, while centralized DTA produces the lowest foraging rate in most maps. These results are in agreement with those of [PERSON] (2018), where self-organized DTA is better when the environment changes rapidly. Moreover, in regard to the expiry rate (Figure 6), centralized DTA also produces the worst average expiry rate in all cases, indicating that it is better to have multiple collection zones to treat patients before they die. Nevertheless, ACO, hotspot allocation, and blind allocation behave differently, and the expiry rate results need to be further investigated to compare their performance in each map. However, it can be concluded that hotspot DTA produces the best average expiry rate in most maps when applied to ED_Foraging, followed by ACO and blind DTA. To further investigate the expiry rate in each map and clarify the differences between the methods, the detailed results of each trial are shown in Figure 7-e. In all the maps, it is clear that the centralized method produces significantly worse results than the other methods. In the 4 \(\times\) 4 and 8 \(\times\) 8 maps (Figure 7,b), ACO, hotspot, and blind DTA perform very similarly in all the trials and produce almost the same expiry rate, although the hotspot method produces slightly lower values. However, when the map size is increased, the differences become more apparent. In the 16 \(\times\) 16 map (Figure 7), the hotspot DTA has the lowest expiry rate in most trials, followed by the ACO and blind methods. In the 20 \(\times\) 20 map (Figure 7), the results for the hotspot and ACO methods coincide for the first half of the trials, indicating that they perform similarly, while the blind method is worse than both. However, for the next half of the trials, the hotspot and blind methods are similar, while the ACO method is worse. Finally, in the 40 \(\times\) 40 map (Figure 7), the hotspot and ACO methods perform similarly for the first half of the trials, while the blind method is worse than both. Then, all three methods have similar expiry rates for the next half of the trials. To further investigate the distribution of the results in each map and see how hotspot DTA performs compared to the other methods, the distributions of the results are shown in Figure 7 as box plots. In all the maps, it is clear that centralized allocation performs the worst, as previously found. The result of this method is highly variable, indicating its inconsistency between trials. Moreover, the minimum-maximum-mean lines in the plot show that centralized allocation produces a significantly higher expiry rate than the other methods. In regard to the ACO, hotspot, and blind methods, the distributions (Figure 7) are different between the maps depending on their sizes. In the 4 \(\times\) 4 map, all three methods have similar minimum-maximum-mean values, but the results for the hotspot method are more compressed than those for the ACO and blind methods. This  
Figure 6: Average flexibility of the different methods in terms of the (**a**) foraging and (**b**) expiry rates. indicates that the hotspot method is more consistent with small maps when comparing the expiry rate. In the 8 \(\times\) 8 map, the ACO, hotspot, and blind methods have similar mean values, but the hotspot method has the lowest minimum value; it also has the lowest maximum value, along with the blind method. The ACO method produces slightly worse minimum-maximum results while having a similar dispersion as the hotspot method. On the other hand, the expiry rate for the blind method is more compressed but has more outliers that could affect the results in the long run.