Speeding up the HMC algorithm: Some new results

TL;DR

This paper presents new performance results for the Hybrid Monte Carlo algorithm applied to dynamical clover-improved Wilson fermions, demonstrating that symmetric even-odd preconditioning enhances efficiency, especially with an improved pseudo-fermion action.

Contribution

It shows that symmetric even-odd preconditioning combined with an improved pseudo-fermion action improves HMC performance for dynamical clover-improved Wilson fermions.

Findings

Performance gain of about 1.3 times for lightest quark mass case.

Symmetric preconditioning outperforms asymmetric version.

Improved pseudo-fermion action further enhances HMC efficiency.

Abstract

We give some new performance results for the Hybrid Monte Carlo (HMC) simulation of dynamical clover-improved Wilson fermions using an improved pseudo-fermion action. The generalisation of even-odd preconditioning for the standard Wilson fermion matrix to the clover-improved case is not unique. In the literature the so called symmetric and asymmetric versions are discussed. Most of the previous simulations of dynamical clover-improved Wilson fermions were done with the asymmetric version. Only recently, the JLQCD collaboration has pointed out that the symmetric version leads to a better performance of the HMC algorithm. Here, we show that also in combination with an improved pseudo-fermion action, the symmetric version of even-odd preconditioning leads to a better performance. For our lightest quark mass, which corresponds to $m_{PS}/m_{V} \approx 0.44$, we see a gain in performance by a factor of about 1.3.