  Targeting simulations on parallel hardware architectures, this paper presents
computational kernels for efficient computations in mortar finite element
methods. Mortar methods enable a variationally consistent imposition of
coupling conditions at high accuracy, but come with considerable numerical
effort and cost for the evaluation of the mortar integrals to compute the
coupling operators. In this paper, we identify bottlenecks in parallel data
layout and domain decomposition that hinder an efficient evaluation of the
mortar integrals. We then propose a set of computational strategies to restore
optimal parallel communication and scalability for the core kernels devoted to
the evaluation of mortar terms. We exemplarily study the proposed algorithmic
components in the context of three-dimensional large-deformation contact
mechanics, both for cases with fixed and dynamically varying interface
topology, yet these concepts can naturally and easily be transferred to other
mortar applications, e.g. classical meshtying problems. To restore parallel
scalability, we employ overlapping domain decompositions of the interface
discretization independent from the underlying volumes and then tackle parallel
communication for the mortar evaluation by a geometrically motivated reduction
of ghosting data. Using three-dimensional contact examples, we demonstrate
strong and weak scalability of the proposed algorithms up to 480 parallel
processes as well as study and discuss improvements in parallel communication
related to mortar finite element methods. For the first time, dynamic load
balancing is applied to mortar contact problems with evolving contact zones,
such that the computational work is well balanced among all parallel processors
independent of the current state of the simulation.
