## 5 Results Using Test Data Obtained with FEM Model
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**OF and** & \multicolumn{5}{c}{**Method**} \\
**Parameters** & \multicolumn{2}{c}{**DE/rand/1/exp**} & **DE/rand/2/exp** & **DE/best/1/bin** & **TLBO** & **ABC** \\ \hline \multirow{3}{*}{OF (\%)} & B & 1.1544 & 1.1544 & 1.1544 & 1.1544 & 1.1658 \\  & W & 1.6153 & 1.5850 & 3.8752 & 1.5699 & 1.4157 \\  & M & 1.1997 & 1.1797 & 1.5044 & 1.4256 & 1.2230 \\  & SD & \(1.3042\times 10^{-1}\) & \(9.7386\times 10^{-2}\) & \(3.8659\times 10^{-1}\) & \(1.7582\times 10^{-1}\) & \(5.1185\times 10^{-2}\) \\ \hline \(\rho_{1}\) (\(\Omega\)m) & B & 201.39 & 201.44 & 201.38 & 201.39 & 201.70 \\ \hline \(h_{1}\) (m) & B & 52.29 & 52.33 & 52.29 & 52.30 & 52.52 \\ \hline \(\rho_{2}\) (\(\Omega\)m) & B & 3473.14 & 2659.33 & 3500.00 & 3499.54 & 1011.04 \\ \hline \(h_{2}\) (m) & B & 2.74 & 3.57 & 2.71 & 2.71 & 9.30 \\ \hline \(\rho_{3}\) (\(\Omega\)m) & B & 5.00 & 5.00 & 5.00 & 5.00 & 6.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: OF and best value of the calculated parameters for 50 independent runs for the BF subarea. For easier conclusions, the mean OF values for all five optimization methods and all nine subareas are shown in Figure 8.  
Based on Tables 5-13 and Figure 8, the following can be seen:  
* ABC was better than other methods in the case of seven subareas (AD, AE, AF, BD, CD, CE, and CF). * In the case of BE, DE/rand/2/exp and TLBO were slightly better than ABC. * In the case of BF, DE/rand/1/exp and DE/rand/2/exp were slightly better than ABC. * In the case of the CD subarea, ABC was 19% better than the next best. * In the case of the CE subarea, ABC was 23% better than the next best. * In the case of the CF subarea, ABC was 25% better than the next best. Taking into account the given findings, we can claim that the ABC method is the best among the tested methods for the problem considered. When comparing evolutionary methods, the convergence of each method is also important. Due to the use of the random generator, each calculation flow is different. Therefore, the average convergence speed of each method was determined. The results are shown in Figure 9, where the average FEs required to achieve OF < 10%, OF < 9%, etc., with the OF values shown. Based on Figure 8, it can be seen that the convergence of DE/best/1/bin was fastest. The convergences of DE/rand/1/exp, DE/rand/2/exp, and TLBO were similar. The convergence of ABC was fastest in the case of CD and slowest for all the other cases. It is interesting that ABC gave the best results despite the slowest convergence. As mentioned, the calculation time is also an important calculation parameter, due to the nine subareas. The mean calculation times for 50 independent runs for the five optimization methods and all nine subareas are presented in Table 14.  
Based on Table 14, it can be seen that the calculation times of the ABC method are longer than those of the other methods. The different calculation times are due to the different search spaces in the cases of different methods. The time of numerical integration of expression (3) depends on the soil parameters during the optimization, which leads to the searched soil parameters. Figure 8: Mean OF values for all five optimization methods and all nine subareas.