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Chen et al. J Mater Inf 2023;3:10  https://dx.doi.org/10.20517/jmi.2023.06       Page 9 of 19

               Table 6. List of the ML models based on SVM or ANN with good performance on small-sized databases
                Target                 Size of database       Algorithm     Performance            Ref.
                Phase prediction       118                    ANN           Accuracy = 0.992       [127]
                Phase prediction       401                    ANN           Accuracy = 0.943       [130]
                Phase prediction       550                    SVM           Accuracy = 0.887       [134]
                Phase prediction       322                    SVM           Accuracy = 0.9384      [139]
                Phase prediction       391                    ANN           Accuracy = 0.92        [142]
                Phase prediction       407                    SVM           Accuracy = 0.9743      [149]
                Phase prediction       209                    ANN           Accuracy = 0.9297      [150]
                Hardness prediction    155                    SVM           RMSE = 31              [122]
                                                                             2
                Hardness prediction    214                    SVM           R  = 0.873             [146]
                                                                             2
                Hardness prediction    370                    SVM           R  = 0.8836            [147]
                                                                             2
                Hardness prediction    53                     ANN           R  = 0.8575            [151]
                                                                             2
                Strength prediction    231                    ANN           R  = 0.9702            [152]
                                                                             2
                EHEA Design            321                    ANN           R  = 0.9663            [79]
                                                                             2
                EHEA Design            100                    SVM           R  = 0.916             [80]
               ANN: Artificial neural network; EHEA: Eutectic high entropy alloys; RMSE: root mean square error; SVM: support vector machine.














                                                                                                       [126]
                Figure 4. Confusion matrix of the SVM, ANN models, and the predicted results. Reproduced with permission from Jaiswal  et al.  .
                Copyright 2021, Elsevier. ANN: artificial neural network; SVM: support vector machine.

                      [147]
               (RMSE)  are usually used for regressors. It is noteworthy that the performance of the ML models should
               be judged not only by existing data (i.e. data in the database) but also by the “unseen” data (data out of the
               database). In addition to the above-mentioned numerical evaluations, experimental validation is therefore
                                                                                                       [126]
               needed that produces unseen data to test the predictability of the ML models. For instance, Jaiswal et al.
               used two different ML models (i.e., SVM and ANN) for the phase prediction of the CoCuFeNi  system.
                                                                                                  x
               While both ML models achieve a similar numerical accuracy (~0.85), it appears that the ANN model can
               predict the result being consistent only with the experimental observation for low Ni content (x = 5, 10). In
               contrast, the SVM model can predict the results correctly only for high Ni content (x = 15, 20, 25), as
               illustrated in Figure 4.


               Among the above-mentioned ML algorithms, the SVM and ANN are the ones that are widely used in the
                                                                                            [148]
               design of HEAs, including EHEAs, due to their good performance on small-sized databases , as shown in
               Table 6 [79,80,122,127,130,134,139,142,146,147,149-152] . Here, we note that the reported ML models for EHEAs with good
               performance are mostly regressors, outperforming the classifier. This phenomenon could be attributed to
               the data imbalance in the EHEA database (i.e. the number of EHEAs is significantly smaller than that of
                                [153]
               non-eutectic HEAs) . In practice, data shortage and/or imbalance could be an issue, particularly for the
               design of EHEAs. To mitigate the negative effect, people proposed a few methods, including (1) data
                                                                                  [154]
               rebalancing with the Synthetic Minority Oversampling Technique (SMOTE)  and the Tomek links for
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