riper is a module for the calculation of ground state energies for molecular and periodic systems at the DFT level. In this program a combination of the Resolution of Identity (RI) approximation and continuous fast multipole method (CFMM) is applied for efficient evaluation of the electronic Coulomb term. For the exchange-correlation term an octree-based adaptive numerical integration scheme is used. For the molecular systems a low-memory modification of the RI approximation is implemented aimed specifically for calculations on very large molecules. More details are given in Refs ,  and .
Current functionalities and limitations of riper are: