As explained previously, the proposed method was designed based on four ideas. To investigate the contribution of each idea to the overall performance, we implemented the five variants listed in Table : (1) SMC-RECUR-GTM-SR-PL, (2) SMC-RECUR-GTM, (3) SMC, (4) Random, and (5) Random-RECUR. The meanings of the abbreviations attached to each method are as follows: