关键词: 粗糙集，简化决策表，正区域，核，算法复杂度

Abstract: At present, the main method of designing algorithm for computing the core based on the positive region is discernibility matrix In this method, the core is found by discovering all discernibility elements of discenibihty matrix So this method is very time consuming. On the foundation of the simplified decision table and simplified discernibility matrix, if the objects with condition attribute value of simplified decision table are looked as numbers, they are order. Using the order, the discernibility elements including the core may be turned into a mall quantity of research space. So the core based on the positive region can be found only by searching a small quantity of discernibility elements of the simplified discernibility matrix On this condition, an efficient computing core was designed by integrating the idea of radix sorting. The time complexity and space complexity are O(|C||U|)+O(|C|2|U/C|) and O(|C||U|) respectively.Since the core can be found by searching a small quantity of discerniblity elements of the simplified discernibility matrix in the new algorithm, the efficiency of the new algorithm is improved.

Key words: Rough set, Simplified decision table, Positive region, Core, Algorithm complexity