Simulations at physical quark masses are affected by the critical slowing down of the solvers.Multigrid preconditioning has proved to effectively deal with this problem. The ETM collaboration is performing multigrid accelerated simulations at the physical point to generate Nf = 2 and Nf = 2 + 1 + 1 gauge ensembles. The adaptive aggregation-based domain decomposition multigrid solver, referred to as DD-αAMG, is being used. In this talk we will present our simulation strategy, which consists of an hybrid approach using different solvers, like Conjugate Gradient (CG), multi-mass-shift CG and DD-αAMG. We will discuss the multigrid preconditioning for the non-degenrate twisted mass operator, which represents the strange and the charm quarks, and discuss the performance of the multigrid approach during the integration of the Molecular Dynamics. We will show results on different HPC platforms presenting a speed up of almost an order of magnitude compared to previously done simulations.

Algorithms and Machines