Application of multi-grid solvers in lattice QCD simulations at physical quark masses

Lattice QCD simulations requires to constantly solve thousands or even millions of large linear equations involving the discretised Dirac operator. This is done by using iterative Krylov methods, which become highly efficient if preconditioned via a coarse grid correction. A lattice QCD library, which implements such multi-grid methods for Wilson-Dirac-type fermions, is given by DDalphaAMG. In my talk I will discuss how we applied multi-grid methods, in particular DDalphaAMG, within simulations of twisted mass fermions at physical quark masses. This includes the tuning process as well as its adaptation in rational approximation of the square root. Additional I will discuss challenges of using multigrid solver applications on current and future HPC systems. This includes a discussion on how to scale and speed up the calculation of the coarse grid corrections.