Title: pMR: A high-performance communication library,
Abstract: On many parallel machines, the time LQCD applications spent in communication
is a significant contribution to the total wall-clock time, especially in the
strong-scaling limit. We present a novel high-performance communication library
that can be used as a de facto drop-in replacement for MPI in existing
software. Its lightweight nature that avoids some of the unnecessary overhead
introduced by MPI allows us to improve the communication performance of
applications without any algorithmic or complicated implementation changes. As
a first real-world benchmark, we make use of the pMR library in the coarse-grid
solve of the Regensburg implementation of the DD-$\alpha$AMG algorithm. On
realistic lattices, we see an improvement of a factor 2x in pure communication
time and total execution time savings of up to 20%.