An accurate join for zonotopes, preserving affine input/output relations

Zonotopes are a convenient abstract domain for the precise analysis of programs with numerical variables. Compared to the domain of convex polyhedra, it is less expensive and may easily handle non-linear assignments. However, the classical join operator of this abstract domain does not always preserve linear invariants, unlike the convex hull. We present a global join operator that preserves some affine relations. We end up by showing some experiments conducted on the constrained Taylor1+ domain of Apron.