Lattice QCD with two dynamical Wilson fermions on APE100 parallel systems

摘要

The cost for stochastic sampling of quantum chromodynamics (QCD) vacuum configura- tions outweighs by far the costs of the remaining computational tasks in Lattice QCD, due to the non-local forces arising from the dynamics of fermion loops in the vacuum fluctua- tions. The evaluation of quality and hence efficiency of sampling algorithms is largely deter- mined by the assessment of their decorrelation capacity along the Monte Carlo time series. In order to gain control over statistical errors, state-of the-art research and development on QCD sampling algorithms need substantial amount of teraflops-hours. Over the past years two German--Italian collaborations, SESAM and TXL, carried out exploratory simulations, joining their resources in a meta-computing effort on various computer platforms in Italy and Germany. In this article, we shall discuss the practical aspects of this work, present highlights of autocorrelation measurements, illustrate the impact of unquenching on some fundamental parameters of QCD and describe the lessons to be learned for future, more realistic computer experiments of this kind.