PURPOSE: To shorten the time needed for calculating a satisfactory solution of the optimization problem by providing a constitution where a certain parent genetic code replaces by itself the value of the genes of two or more parent genetic codes with the value of the genes of the parts corresponding to the value of the genes of the parent genetic codes.

CONSTITUTION: In a crossing process of a genetic algorithm, three or more parent genetic codes are selected decisively or in terms of probability as the crossing objects based on some rule. Then a certain parent genetic code replaces the value of the genes of the different parts of two or more other parent genetic codes with the value of its own genes of the parts corresponding to those genetic codes. For instance, the gene d1 of the first parent genetic code is replaced with the gene d2 of the second parent genetic code, the gene d2 is replaced with the gene d3 of the third parent genetic code, and the gene d3 is replaced with the gene d1 respectively among these three genetic codes. Thus various genetic codes are acquired.