Speaker
Description
Clover fermions are widely used in lattice QCD due to their cost effectiveness and O(a) improvement, but the condition number of their Dirac operator grows problematically at small quark masses and large lattice volumes, limiting HMC step sizes and simulation stability. Exponentiated clover fermions have emerged as an alternative that has shown a better-conditioned eigenvalue spectrum, potentially enabling larger molecular dynamics step sizes and improved HMC acceptance rates.
The implementation of the HMC force terms for exponentiated clover fermions is more involved than for standard clover. The force terms require the application of multiple powers of the clover term, which introduces a tradeoff between storing intermediate powers in memory or recomputing them on the fly. We have implemented the latter in Chroma using QDP-JIT for GPU acceleration, with solver support for both the native Chroma inverters and QUDA.
We present strong scaling results from 2+1 dynamical fermion simulations on AMD GPUs on the Frontier supercomputer, using lattice sizes of 16³×32, 24³×48. Performance is compared against standard clover fermions to assess the overhead introduced by the exponentiated action. These results inform the viability of exponentiated clover fermions for gauge field generation on larger ensembles.