RHMC with Block Solvers and Multiple Pseudofermions

by Liam Roger George Keegan (CERN)

Thursday 27 Sept 2018, 14:30 → 15:30 Europe/Zurich

4/2-037 - TH meeting room (CERN)

The dominant cost of most lattice QCD simulations is the inversion of
the Dirac operator required to calculate the force term in the RHMC
update. One way to improve this situation is to use multiple
pseudofermions, which reduces the size and variance of this force and
hence allows a larger integration step size to be used. This means
fewer force term calculations are required, but at the cost of having
to invert the Dirac operator for each pseudofermion field. This
bottleneck can be addressed: recently there has been renewed interest
in the use of block Krylov solvers, which can solve multiple right
hand side vectors with significantly fewer iterations than are
required if each vector is solved using a separate Krylov solver. We
combine these two ideas, achieving a significant speed-up of RHMC
lattice QCD simulations.

Cern2018.pdf