The present invention provides a method, apparatus and article of manufacture for generating hints for use when performing reach-ability analysis of a program such as programmatic representations of hardware circuits. The hints are generated from external inputs to the program which are used in conditional statements of the program. Further such an external input may be excluded from the hints if none of the statements of at least one of the alternative paths following from the conditional statement in which it is used have a data dependency to another statement of the program.