Rule-Tolerant Verification Algorithms for Completeness of Chinese-Chess Endgame Databases

Abstract

Retrograde analysis has been successfully applied to solve Awari [6], and construct 6-piece Western chess endgame databases [7]. However, its application to Chinese chess is limited because of the special rules about indefinite move sequences. In [4], problems caused by the most influential rule, checking indefinitely, have been successfully tackled by Fang, with the 50 selected endgame databases were constructed in concord with this rule, where the 60-move rule was ignored. A conjecture is that other special rules have much less effect on staining the endgame databases, so that the corresponding stain rates are zero or small. However, the conjecture has never been verified before. In this paper, a rule-tolerant approach is proposed to verify this conjecture. There are two rule sets of Chinese chess: an Asian rule set and a Chinese rule set. Out of these 50 databases, 24 are verified complete with Asian rule set, whereas 21 are verified complete with Chinese rule set (i.e., not stained by the special rules). The 3 databases, KRKCC, KRKPPP and KRKCGG, are complete with Asian rule set, but stained by Chinese rules.