Hi, When I use asimut to compile amd.vbe, it needs -bdd parameter, if I only use -b -c, as the tutorial says, it says " Fatal error 101 executing `beh_abl2gex`: unknown terminal operand `'d'` ". I read the manual of asimut , and -bdd means " use BDDs to represent expressions...," that means this parameter is not necessary, just used for accelerating the compiling. Why it is necessary for amd compiling? Thanks. Jie