  In this paper, we report a reimplementation of the core algorithms of
relativistic coupled cluster theory aimed at modern heterogeneous
high-performance computational infrastructures. The code is designed for
efficient parallel execution on many compute nodes with optional GPU
coprocessing, accomplished via the new ExaTENSOR back end. The resulting
ExaCorr module is primarily intended for calculations of molecules with one or
more heavy elements, as relativistic effects on electronic structure are
included from the outset. In the current work, we thereby focus on exact
2-component methods and demonstrate the accuracy and performance of the
software. The module can be used as a stand-alone program requiring a set of
molecular orbital coefficients as starting point, but is also interfaced to the
DIRAC program that can be used to generate these. We therefore also briefly
discuss an improvement of the parallel computing aspects of the relativistic
self-consistent field algorithm of the DIRAC program.
