Lettuce

Description

This repository contains code for carrying out multi-threaded CPU simulations of 4-dimensional SU(3) gauge theory. The primary motivation behind this code is to test different algorithms aimed at alleviating the problem of topological freezing. Some of the results from simulations performed using this code can be found in the following two papers:

[2307.04742] - Parallel Tempered Metadynamics: Overcoming potential barriers without surfing or tunneling
[2210.11453] - Topology changing update algorithms for SU(3) gauge theory

Note that the code is currently undergoing a complete rewrite (to support simulations with dynamical fermions, GPU offloading, and other gauge groups), and the main branch may soon be designated as a legacy branch. The current version lacks tests and contains several areas under active development. Still, if you have any questions, feel free to reach out to me.

Requirements

This project requires Eigen and the PCG PRNG. Both header-only libraries have been included in the repository, so there should be no need to manually install these libraries. Other than that, you need a compiler supporting C++20 (while the current version only rarely uses C++20 features, the upcoming rewrite will heavily rely on concepts).

Building

Since all dependencies are already included in the repository as header files, you can simply compile the code via:

make

Optionally, the flag 'FIXED_SEED' may be set during compilation to seed the inbuilt PRNG class (used for the update algorithms) with a fixed seed:

make FLGS=-DFIXED_SEED

The following parameters need to be known/set at compile-time:

Lattice extents (Nt, Nx, Ny, Nz)
Update algorithm parameters (which type of update algorithms, sweep number, ...):
- Number of update sweeps per algorithm (Metropolis (and number of subsequent hits per link), heat bath, overrelaxation, HMC, ...)
- Use of Metadynamics and related parameters (number of smearing steps for CV, should the bias potential be updated, ...)
- Use of Parallel Tempered Metadynamics and related parameters (how many updates to perform on the measurement stream, tempering swap proposal frequency) Note that it only makes sense to set the 'tempering_enabled' parameter to true if 'metadynamics_enabled' is also set to true

The parameters can be found in LettuceGauge/defines.hpp

Citing Lettuce

If you use this code, please cite the following:

@mastersthesis{EichhornThesis,
  author  = "Eichhorn, Timo",
  title   = "{Slowing Down Critical Slowing Down}",
  school  = "University of Wuppertal",
  year    = "2023"
}

License