Speeding up Variable Reordering of OBDDs

In this paper we suggest a block restricted sifting strategy which is based on the restriction of Rudell s sifting to certain blocks of variables The application of this strategy results in a consider able improvement of the time performance without causing a substantial increase of OBDD size The blocks of variables were determined according to some structural properties re ecting the communi cation complexity within the considered OBDD without using any additional information about its functionality or dependency of variables This assures the general usability of the heuristic and the possibility to use it dynamically