Abstract : State space generation suffers from the typical combinatorial explosion problem when dealing with industrial specifications. In particular, memory consumption while storing the state space must be tackled to verify safety properties. Decision Diagrams are a way to tackle this problem. However, their performance strongly rely on the way variables encode a system. Another way to fight combinatorial explosion is to hierarchically encode the state space of a system.
This paper presents how we mix the two techniques via the hierarchization of a precomputed variable order. This way we obtain a hierarchical static order for the variables encoding a system. This heuristic was implemented and exhibits good performance.