A method includes: classifying sampling points (SPs) into ranks so as to satisfy a condition such as a condition that no SP belonging to a certain rank is dominated by another SP belonging to a rank higher than the certain rank; determining, in ascending order from a lowest rank, whether a first SP belonging to a first rank dominates a second SP belonging to a second rank higher than the first rank. When the first SP dominates, while changing the rank from a rank immediately lower than the first rank to the lowest rank, the first SP and SPs dominating the first SP and included in a first set of the first SP are added to a dominating source set of the second SP, and the first SP and SPs in the first set are excluded from SPs for which the determining is executed with respect to the second SP.