Finally, e orts have been made to make this so ware as developer friendly as possible thanks to a very modular architecture that allows any developer to create his/her own module and to directly bene t from all pre-existing work. e e ciency of the storage as a hash table was measured on a dual socket Intel Xeon E5-2680 v2@2.80GHz processor, taking the water molecule with the cc-pVQZ basis set (115 MOs). e time to access all the integrals was measured by looping over the entire set of ERIs using di erent loop orderings. e results are given in Table , the reference being the storage as a plain four-dimensional array.