Grid

C++ code examples for the Grid library (www.github.com/paboyle/Grid)

Abstract

This repository contains some example programs for the Grid library. This repo addresses people that like to do Lattice Quantum Chromodynamic (LQCD) and want to try out this new library. The examples show how to use Grid's features. They also provide some benchmarks whose corresponding Chroma files can be found in my Chroma repo (www.github.com/fim16418/Chroma) and used for comparison of the two libraries. For the compilation I used the release/v0.7.0 branch of the Grid repository.

The files

rng.cpp

This example shows how to set up an instance of GridCartesian and how to fill it with random numbers from the GridParallelRNG (Random Number Generator).

gridThreads.cpp & ompThreads.cpp

When it comes to using multiple threads, one can either use the OpenMP (omp.h) or Grid functions. As can be seen in gridThreads.cpp, the number of threads cannot be increased once set (which should not be done anyways). I would suggest users to use the functions from gridThreads.cpp.

peekPoke.cpp & peekPoke2.cpp

Accessing tensors for read (peek) and write (poke) operations can be done via two different ways. Either the peek & poke functions are used in the way presented in peekPoke.cpp or the elements are accessed directly as done in peekPoke2.cpp

benchmarkCorrelation.cpp & benchmarkDerivative.cpp

Those programs serve as benchmarks for Grid's performance while computing the correlation (two-point) function (with/without derivative).

Benchmark_su3.cpp

This file is a modified version of the Benchmark_su3.cc file from the Grid repository. Command line arguments where added to make it more comfortable to use (e.g. with bash scripts).

BenchmarkSu3.cpp

Same as benchmarkCorrelation but only featuring a LatticePropagator x LatticePropagator multiplication.

loop.sh & slurm.sh

In order to run the benchmarks for various lattice sizes and other parameters, this bash script can be modified and executed.

benchmarkMDA[x].cpp

Those benchmarks aim to test different ways of calculating the Meson Distribution Amplitude (MDA) with Grid.

mdaFull.cpp

Implementation of an efficient algorithm for computing the MDA of propagator combinations involving their derivatives.