Lattice calculations of Quantum Chromodynamics (QCD) are continuously becoming more realistic. Where Ukawa famously concluded only fourteen years ago that simulations including two physically light sea quarks are basically impossible even with today’s computers, algorithmic developments over the last years have changed this situation drastically. Nowadays up and down quark masses light enough to control the chiral extrapolation reliably are standard and also the sea quark effects of strange (and charm) quark are included.Modern lattice simulations are an intricate interplay between a large variety of numerical methods on one side and the computer hardware on the other side. The main areas of progress have been the solvers used for the Dirac equation, fermion determinant factorisations and better integrators for the molecular dynamics which is at the heart of most algorithms used for QCD simulations.In lattice QCD simulations the path integral is computed via a Markov Chain Monte Carlo method. In virtually all projects with dynamical fermions a variant of the Hybrid Monte Carlo algorithm is employed to generate the Markov chain, where the fields are updated using molecular dynamics. But there is considerable freedom in how to include the fermion determinant into the simulation. Factorisations of this determinant have been essential in the progress of recent years, being successful in particular together with improved integrators of the molecular dynamics.The solution of the Dirac equation constitutes the most computer time consuming element of simulations with fermions. The dramatic speedup for small fermion mass due to locally deflated solvers5, 6 has therefore had a significant impact on what is possible in the simulations. These algorithms have practically eliminated the increase in cost of the solution as the quark mass is lowered
