In this paper, we present a novel method to compute the number of all stack filters. In our approach, the Boolean function is represented by Hasse diagram. Owing to the decomposition property of Hasse diagram, the n-variable positive Boolean function can be synthesized by positive Boolean functions with variable size fewer than n - 2 which leads to the reduction of memory requirement. Besides, the positive Boolean functions of ii variables can be partitioned into 2(n) + 1 parts according to the cardinality of all the truth input vectors instead of the minimals of truth input vectors. This partition method reveals the symmetrical distribution behavior of positive Boolean functions, which results in the saving of the total computation effort nearly by half (C) 1998 Published by Elsevier Science B.V. All rights reserved.