On the real arity of multiparent recombination

Several papers have reported experimental results for multiparent recombination operators, looking at the effects of using more parents. Tacitly, these studies assume that the number of parents (the arity of the given recombination operator) tells how many old individuals contribute to a new one by passing their genetic information to it. We point out that this assumption is not valid for a number of well-known recombination operators and distinguish parents and donors, the latter being those parents that really deliver information to the offspring. We perform a mainly theoretical analysis on the number of donors. We also consider the mechanisms for choosing the alleles for a child and find indications for a too strong genetic drift for occurrence-based scanning. Experimental results are provided to support theoretical estimates and predictions