Authors: Huayang Xie, Mengjie Zhang, Peter Andreae
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Abstract: The standard tournament selection samples individuals with replacement. The sampling-with-replacement strategy has its advantages but also has issues. One of the commonly recognised issues is that it is possible to have some individuals not sampled at all during the selection phase. The not-sampled issue aggravates the loss of diversity. However, it is not clear how the issue affects GP search. This paper uses a round-replacement tournament selection to investigate the importance of the issue. The theoretical and experimental results show that although the issue can be solved and the loss of diversity can be minimised for small tournament sizes, the different selection behaviour in the round-replacement tournament selection cannot significantly improve the GP performance. The not-sampled issue does not seriously affect the selection performance in the standard tournament selection.