A linear-time algorithm to find modules of fault trees

A module of a fault tree is a subtree whose terminal events do not occur elsewhere in the tree. Modules, which are independent subtrees, can be used to reduce the computational cost of basic operations on fault trees, such as the computation of the probability of the root event or the computation of the minimal cut sets. This paper presents a linear time algorithm to detect modules of a fault tree, coherent or not, that is derived from the Tarjan algorithm to find strongly connected components of a graph. The authors show, on a benchmark of real fault trees, that their method detects modules of trees with several hundred gates and events within few milliseconds on a personal computer