Simple and Precise Widenings for H-Polyhedra

While the definition of the revised widening for polyhedra is defined in terms of inequalities, most implementations use the double description method as a means to an efficient implementation. We show how standard widening can be implemented in a simple and efficient way using a normalized H-representation (constraint-only) which has become popular in recent approximations to polyhedral analysis. We then detail a novel heuristic for this representation that is tuned to capture linear transformations of the state space while ensuring quick convergence for non-linear transformations for which no precise linear invariants exist.