We present EDIpack, an exact diagonalization package to solve generic quantum impurity problems. The algorithm includes a generalization of the look-up method introduced in Ref. [1] and enables a massively parallel execution of the matrix-vector linear operations required by Lanczos and Arnoldi algorithms. We show that a suitable Fock basis organization is crucial to optimize the inter-processors communication in a distributed memory setup and to reach sub-linear scaling in sufficiently large systems. We discuss the algorithm in details indicating how to deal with multiple orbitals and electron-phonon coupling. Finally, we outline the download, installation and functioning of the package. Program summary: Program title: EDIpack CPC Library link to program files: https://doi.org/10.17632/2hxhw9zjg9.1 Code Ocean capsule: https://codeocean.com/capsule/3537659 Licensing provisions: GPLv3 Programming language: Fortran, Python External dependencies: CMake (>=3.0.0), Scifortran, MPI Nature of problem: The solution of multi-orbital quantum impurity systems at zero or low temperatures, including the effective description of lattice models of strongly correlated electrons, are difficult to determine. Solution method: Use parallel exact diagonalization algorithm to compute the low lying spectrum and evaluate dynamical correlation functions.
