The most significant technique we u

The most significant technique we use to address the cost of fitness evaluation is to take advantage of a special Characteristic of the problem domain, namely that we can separately evaluate the quality of a solution and the validity of a solution. Only valid (or as explained below, nearly valid) solutions are of interest, but among those we want to minimize the total weight. We can calculate the weight of a solution much faster than we can check its validity, and so we use this capability to help us decide whether we want to check the validity of a solution at all.