Rank: a tool to check program termination and computational complexity

International audienceProving the termination of a flowchart program can be done by exhibiting a ranking function, i.e., a function from the program states to a well-founded set that strictly decreases at each program step. In a previous paper 1 , we proposed an algorithm to compute multidimensional affine ranking functions for flowcharts of arbitrary structure. Our method, although greedy, is provably complete for the class of rankings we consider. The ranking functions we generate can also be used to get upper bounds for the computational complexity (number of transitions) of the source program. This estimate is a polynomial, which means that we can handle programs with more than linear complexity. This abstract aims at presenting R ANK, the tool that implements our algorithm