Abelian-Higgs cosmic string evolution with multiple GPUs
  Topological defects form at cosmological phase transitions by the Kibble
mechanism. Cosmic strings and superstrings can lead to particularly interesting
astrophysical and cosmological consequences, but this study is is currently
limited by the availability of accurate numerical simulations, which in turn is
bottlenecked by hardware resources and computation time. Aiming to eliminate
this bottleneck, in recent work we introduced and validated a GPU-accelerated
evolution code for local Abelian-Higgs strings networks. While this leads to
significant gains in speed, it is still limited by the physical memory
available on a graphical accelerator. Here we report on a further step towards
our main goal, by implementing and validating a multiple GPU extension of the
earlier code, and further demonstrate its good scalability, both in terms of
strong and weak scaling. A $8192^3$ production run, using $4096$ GPUs, runs in
$33.2$ minutes of wall clock time on the Piz Daint supercomputer.
