“…Problems GEN(C, F π , X ) and GEN(C, G π , Y) arise in many practical applications and in a variety of fields, including artificial intelligence [14], game theory [18,19], reliability theory [8,12], database theory [9,14,17], integer programming [4,6,20], learning theory [1], and data mining [2,6,9]. Even though these two problems may be NP-hard in general (see e.g.…”