Parallelizing a 1-Dim Nagel-Schreckenberg Traffic Model

The Nagel-Schreckenberg model is a stochastic one-dimensional traffic model. In this assignment, we guide students through the process of implementing a shared-memory parallel and reproducible version of an existing serial code that implements this model, and to analyze its scaling behavior. One of the key elements in this traffic model is the presence of randomness, without which it would lack realistic phenomena such as traffic jams. Its implementation thus requires techniques associated with Monte Carlo simulations and pseudo-random number generation (PRNG). PRNGs are notoriously tricky to deal with in parallel when combined with the requirement of reproducibility. This assignment was created for the graduate course PHY1610 Scientific Computing for Physicists at the University of Toronto, which had its origin in the training program of the SciNet HPC Consortium, and is also very suitable for other scientific disciplines. Several variations of the assignment have been used over the years.Comment: To be presented at the "EduHPC-23: Workshop on Education for High-Performance Computing" to be held in conjunction with SC23. Starter code and handout can be found in the "complimentary" material section or the GitHub repository https://github.com/Practical-Scientific-and-HPC-Computing/Traffic_EduHPC-2

Software-Enhanced Teaching and Visualization Capabilities of an Ultra-High-Resolution Video Wall

This paper presents a modular approach to enhance the capabilities and features of a visualization and teaching room using software. This approach was applied to a room with a large, high resolution (7680$\times$4320 pixels), tiled screen of 13 $\times$ 7.5 feet as its main display, and with a variety of audio and video inputs, connected over a network. Many of the techniques described are possible because of a software-enhanced setup, utilizing existing hardware and a collection of mostly open-source tools, allowing to perform collaborative, high-resolution visualizations as well as broadcasting and recording workshops and lectures. The software approach is flexible and allows one to add functionality without changing the hardware.Comment: PEARC'19: "Practice and Experience in Advanced Research Computing", July 28-August 1, 2019 - Chicago, IL, US

Short-time fluctuations of displacements and work

A recent theorem giving the initial behavior of very short-time fluctuations of particle displacements in classical many-body systems is discussed. It has applications to equilibrium and non-equilibrium systems, one of which is a series expansion of the distribution of work fluctuations around a Gaussian function. To determine the time-scale at which this series expansion is valid, we present preliminary numerical results for a Lennard-Jones fluid. These results suggest that the series expansion converges up to time scales on the order of a picosecond, below which a simple Gaussian function for the distribution of the displacements can be used.Comment: 10 pages, 3 figure

Discontinuous Molecular Dynamics for Rigid Bodies: Applications

Event-driven molecular dynamics simulations are carried out on two rigid body systems which differ in the symmetry of their molecular mass distributions. First, simulations of methane in which the molecules interact via discontinuous potentials are compared with simulations in which the molecules interact through standard continuous Lennard-Jones potentials. It is shown that under similar conditions of temperature and pressure, the rigid discontinuous molecular dynamics method reproduces the essential dynamical and structural features found in continuous-potential simulations at both gas and liquid densities. Moreover, the discontinuous molecular dynamics approach is demonstrated to be between 2 to 100 times more efficient than the standard molecular dynamics method depending on the specific conditions of the simulation. The rigid discontinuous molecular dynamics method is also applied to a discontinuous-potential model of a liquid composed of rigid benzene molecules, and equilibrium and dynamical properties are shown to be in qualitative agreement with more detailed continuous-potential models of benzene. Qualitative differences in the dynamics of the two models are related to the relatively crude treatment of variations in the repulsive interactions as one benzene molecule rotates by another.Comment: 14 pages, double column revte