https://hal.inria.fr/inria-00360243Le Gall, FrançoisFrançoisLe GallERATO-SORST Quantum Computation and Information Project - Japan Science and Technology AgencyEfficient Isomorphism Testing for a Class of Group ExtensionsHAL CCSD2009polynomial-time algorithmsgroup isomorphismblack-box groups[INFO.INFO-CC] Computer Science [cs]/Computational Complexity [cs.CC][INFO.INFO-DM] Computer Science [cs]/Discrete Mathematics [cs.DM]Loria, PublicationsSusanne Albers and Jean-Yves Marion2009-02-10 17:01:182017-11-29 10:27:372009-02-11 11:13:31enConference papersapplication/pdf1The group isomorphism problem asks whether two given groups are isomorphic or not. Whereas the case where both groups are abelian is well understood and can be solved efficiently, very little is known about the complexity of isomorphism testing for nonabelian groups. In this paper we study this problem for a class of groups corresponding to one of the simplest ways of constructing nonabelian groups from abelian groups: the groups that are extensions of an abelian group A by a cyclic group Zm. We present an efficient algorithm solving the group isomorphism problem for all the groups of this class such that the order of A is coprime with m. More precisely, our algorithm runs in time almost linear in the orders of the input groups and works in the general setting where the groups are given as black-boxes.