  We present the results of an effort to accelerate a Rational Hybrid Monte
Carlo (RHMC) program for lattice quantum chromodynamics (QCD) simulation for 2
flavours of staggered fermions on multiple Kepler K20X GPUs distributed on
different nodes of a Cray XC30. We do not use CUDA but adopt a higher level
directive based programming approach using the OpenACC platform. The lattice
QCD algorithm is known to be bandwidth bound; our timing results illustrate
this clearly, and we discuss how this limits the parallelization gains. We
achieve more than a factor three speed-up compared to the CPU only MPI program.
